Observational Astronomy Reports -- February, 2001
"Penta"-zium
Date: Friday, February 2nd 2001Earlier in the day, I layed out all my equipment on the back deck for "sunning". This particular ritual involves warming everything up to drive off accumulated condensation. Typically, the equipment (OTA, diagonal, eyepieces, filters, etc.) is exposed just long enough to warm to the touch and drive off visible dew. On this occasion, I noticed quite a bit of condensation on the primary mirror itself. To banish this I had to open the cap over the focuser and spin the telescope barrel toward (but not directly at) the sun. This method means more than the usual heat build up. I expected that evening cool-down problems would occur resulting in "tube currents".
The phenomenon of "tube currents" is pretty straightforward to understand. Heat rises inside the telescope tube. The motion (and density variations) of the air distorts light passing through it. You end up with "comatose" star images. In a Maksutov-Cassegrain both ends of the tube are blocked, and the phenomenon can persist quite a while. (An hour is not uncommon in my scope.) During cool down, the scope is OK for diffuse deep-sky objects, but poor for anything possessing fine detail (like Jupiter) or tight clearances (like double stars). Most nights I don't have problems with currents. (It normally doesn't overheat.) Tonight was different.
My usual check of Iota showed poor resolution. The presence of the moon, along with high thin clouds, meant that I could only just make out the 12Mag field star at 180x. Checking a few bright stars (for "twinkling"), I concluded that stability was better than the Iota split suggested. Turning the scope on Sirius (magnitude -1.4) I de-focused the image and looked for vertical distortion in the diffraction rings. The taletale "thin tear drop" was there. I decided to put off double-star work and track down open cluster NGC1245 in Perseus.
Even with a collective magnitude of 6.9, this particular open cluster could not be definitively seen in the finderscope. Basically the object was too close to the moon. Light scatter polluted the finder field. (No trouble seeing the crosshairs tonight.) Complicating all this is the fact that thios particular region of Perseus is dominated by an extended field of stars referred to as "MEL20". NGC1245 is located less than one arc-minute away from MEL20's southwestern border. 1245 is also about as compact as the MEL20 region. All of this makes identifying 1245 very difficult. I made numerous passes at triangulating between Alpha and Iota Perseus before finally deciding that I had actually lit on the cluster.
The cluster itself is quite unusual in configuration. It possesses no sense of a core. In fact this group of 40-50 stars has two voids separated by a string of 8th and 9th magnitude stars. The voids and stars that separate (and circumscribe) them give the cluster a "B" shape. (I was also reminded of the Mandelbrot set by the configuration.) The "B" is oriented roughly along the north-south axis. That axis extends perhaps 40 arc-minutes. (The east-west axis perhaps 30.) West of the "B"'s dimple are six or seven ninth and tenth magnitude stars. These resemble an arrowhead. The point again to the west. A hint of unresolved nebulosity is suspected. This could prove to be dimmer stars or perhaps the matrix out of which the cluster formed.One other thought came to mind while observing this cluster. Our own local region of space, consisting of more than the usual number of stars - many of which are also brighter than the norm -- may very well make up a "cluster" similar to NGC1245.
By the time I found 1245 and took the time to view it and write up my field notes the scope had stabilized. A quick check of Sirius (de-focused) confirmed this and I decided to spend time viewing Zeta Orionis (and environs).
NOTE: On the notion that the object described above was not, in fact, NGC1245 I did a little research on the Internet. The real "1245" is described as "densely packed" possessing an integrated magnitude of 8.4 and an apparent field of 10 arc-minutes circular. I'm not sure where my original figures came from but it is clear that I need to revisit this region of space and determine if I can find an object that better matches this description...
Zeta is the southeastern star of The Hunter's Belt". It consists of a tight (separation 2.5 arc-seconds), bright (magnitudes 2.0 & 5.7) double and a more remote 9th magnitude come (at roughly 1 arc-minute). Success at splitting this pair cleanly requires excellent seeing conditions for all scopes (due to the relative brightness of both stars and the interaction of their individual diffraction rings). On this particular evening, and at 180X, the secondary showed a nice spurious disk while the primary had considerable "light scatter". So there was effectively no "open space" between the two to be seen - though both were visible. The primary itself is brilliantly white and the secondary a more placid version of the same color. The come looked grey blue. The primary lies between the secondary and the come. (The secondary due south of the primary and the come slightly east of north.) A quick check at 70X showed the come (although 180 gave the brighter presentation). At that same magnification Zeta was definitely "elongated" -- the primary and secondary's spurious disks fused at the limits.
While in the region, I pulled out the 25mm Plossl with OIII filter. (I believe the Plossl passes slightly more light than the 25mm Ultrascopic though it doesn't have as wide a field of view.) Addition of the filter winked out the ninth magnitude come. Star disks became even smaller. The brightness of the Zeta pair also extinguished quite a bit. The object now was to scan the region for nebulosity. Several "mounds" of luminosity were faintly detectable. One located about 15 arc-minutes east of Zeta (NGC2024) could be made out vaguely without the filter. The other (about 30 minutes south -- NGC2023) could not. There may have been other mounds in the region but these two were enough for an initial scan. Neither of the mounds were directly aligned with stars -- so star haze was not a factor. Incidentally, if I hadn't recently confirmed NGC604 in M31 I probably wouldn't be as confident about "seeing" these two light mounds. Both were on the fringes of detection (under the present conditions).
Given the stability of the air, it's relative warmth and dryness, it made sense to visit M42 and the Trapezium of stars in its midst. One object I had in mind was to see if I could make out the "brightness cliff" to the south of the Trapezium (opposite the "tongue of darkness"). A second was to determine if other members of the Trapezium group could be detected. Finally, fellow amateur Otto Piechewski had mentioned the wealth of detail he had seen in M42 at high magnifications. I wanted to follow up on this as well.
Despite the moon and the high thin clouds, M42 gave a wonderful appearance this evening. Nebulosity was quite extensive both with and without an OIII filter. Trapezium members looked especially sharp and bright. The darkness cliff was just directly perceptible at 70X. I switched over to the 10mm Ultrascopic. At 180X the nebulosity lost some of its "whiteness". However, the darkness cliff was obvious. Billowy nebular folds could be made out all around it. Calling it a "cliff" made good sense. But this was no "sea cliff". It is more akin to the roll off within the ocean where the continental shelf drops away into the depths. In a phrase the whole thing "abounded in a wealth of subtle detail". Otto was right. Even at 180X there was plenty of light to go around. Instead of bleeding it out, the additional magnification revealed details of exceptional interest to the eye.
Before dwelling on Theta Orionis (The Trapezium) in detail, I decided to scan around the M42 region for other delights. Just to the north (and slightly toward the east) is an 8th magnitude star surrounded by considerable nebulosity. In the past I had always assumed that this was simply an extension of the main nebula and therefore hadn't given it much notice. However, this region apparently has its own designation -- M43 to be exact. On it's own, M43 would probably be counted one of the more easily observed (and more highly regarded) nebulae in the heavens. Its proximity to the far more spectacular M42 causes it to pale and be taken for granted (if not be completely overlooked).
As nice as M43 may be, it is perhaps less interesting to the eye than the fine collection of 7th and 8th magnitude stars 30 arc-minutes to the south (and slightly west) of the main event (M42). This loose cluster of approximately 20 stars gives the appearance of an ellipse (or "noose") attached to a beam. At the base of the ellipse is a beautiful triple star of roughly the 4th, 7th and 10th magnitudes (colors: yellow, gold and turqoise). Separation is probably less than 10 arc-seconds on the main pair with the tertiary out at about 45 arc-seconds.
NOTE: After the fact I reviewed Webb's "Celestial Objects for Common Telescopes" The "triple" is Iota Orionis. Webb gives magnitudes 3.2 and 7.3 separated by 11.3 arc-seconds. The third star is of the 11th magnitude and lies 49 arc-seconds distant. Webb terms it a come. By this is meant a field star -- probably not part of the system per se. (Traditionally any star more than 35 arc-seconds distant is normally ruled out as a member of a system and is regarded as a come until some proper motion indicates that it revolves around the primary in some fashion.) There is no suggestion that the "Noose with Crossbeam" group is a designated open cluster -- but I suspect that it is entitled to such an appellation since many of it's component's demonstrate "family ties".
After drinking in the ocean of M42 detail for awhile, and exploring the neigboring region, I shifted over to the Trapezium members in earnest. At 180X members were well spread out, but more importantly the light spill was minimum along with spurious image sizes. Comming into this I had no idea as to where the two 11th magnitude components were to be found. So I started a search pattern looking around and between the four main components. While making this search, I began to notice that the region immediately around the trapezium was "darker" than neighboring regions. Further to the north (and slighlty east) I also detected a pair of 10th (and possibly 11th magnitude) stars emersed in nebulosity. With more "noticing" I began to repeatedly (but not continuously) detect a dim 11th magnitude star between the southeast and northeast members. Soon confidence over took me and made the admission: "This is it". A fifth traepezium member had been found.
The star in question is actually closer to but slightly outside the irregular square made up by the four members of the trapezium. It looked to be about 5 arc-seconds from the southeast member. The configuration looks something like this:
south (51)*[C] (67)*[A] (110)*[E] west (67)*[D] (79)*[B]
A second 11th magnitude star was also hinted at between C and D [F] but I decided that confirmation of this component is something to look forward to on a later occasion.
Having confirmed this fifth component, I was ready to break things down, pack the hatchback and head home. Just as I was about to settle into the cab, I felt a warmth and gratitude spread through my being. Despite it's demands and difficulties, and irrespective of its origins, the universe is an extraordinary place in which to live, and move, and have being. Earthquakes may rock the soil beneath our feet. Asteroids may pummel the earth from above our heads. Droughts may fill our bellies with thirst and hunger. Personal catstrophies may strike us down. The long haul of survival in a competitive world may weary us. But there are moments when none of it matters. A vaster perspective is possible, life is worth all the marbles.to: top of page
"Seven Sisters and Their Many Cousins"
Date: Saturday, February 3, 2001Headed back up to the ridge this evening to revisit a few of last evenings observations and continue to advance the observing plan (before the moon becomes overpowering). Some good work can be accomplished regardless of the moon, however most of that work requires steady skies. (Examples along this line are lunar --of course--, planetary, and double-star observations). Finally, even when skies are bright and relatively unstable, it is still possible to study open clusters, since such clusters are generally easy to locate and describe even under poor seeing circumstances.
As it turned out, stability was poor this evening (Iota Cassiopeia was a "dirty" split.) Transparency was acceptable (as long as the scope -- and eyes -- were directed well away from the moon. (The 12th magnitude Iota field star was direct at 120X.)
After assessing the seeing, I turned the scope on NGC1981 (located roughly 1 degree north of the Great Nebula in Orion). 1981 (it was the best of years-- it was the worst of years) displayed 20 to 30 5th to 12th magnitude stars with an apparent size of roughly 25 X 35 arc-minutes. Orientation is along the east-west axis. The two brightest stellar components are found at the southeast perimeter of the cluster. A "backbone" of about a half dozen 5th through 8th magnitude stars extends just west of the bright pair. The arrangement of these stars is in rough order of decreasing magnitude (increasing brightness). To the west of the northern half of this backbone is an elongated circlet of 7 to 12th magnitude stars. Opposite this circlet (to the east) are a small number of additional 9th and 10th magnitude components.
Using the 25mm ep with OIII filter I inspected the region around NGC1981. Roughly 20 arc-minutes south of 1981 is a small "W" of 5th through 10th magnitude stars. The brightest star (the southeastern) is steeped in the nebula M42. Other stars in the asterism show nebula sign (subtle variations in surface brightness). West of the circlet forming the northwest frontier of 1981 is a hint of an extended "bridge" of nebulosity perhaps 10 arc-minutes in height by 20 arc-minutes in length. The "bridge" itself leads to a small group of 7th to 10th magnitude stars. (These take the form of a rough parallelogram.) Finally 15 arc-minutes north of the circlet is an 8X8 arc-minute nebular mound. As I scanned the entire region, I was constantly aware of "textural" variations in luminosity. (Almost) needless to say, everything cited above needs to be checked on a clear moonless night.
Despite the poor stability, I took a quick 180X look at the Trapezium. Only the four main stars were visible. Members showed over-large and somewhat unstable spurious images (non-airy disks). Not the best conditions in which to makeout 11th magnitude companions separated by a mere 4 arc seconds.
In the double star mood, I swung the scope over to Gemini where I carefully compared views of Castor and Pollux. At 70X, Castor (the westerly bright twin) was obviously elongated. (Pollux was not.) Remembering that the OIII filter helped eliminate lightscatter, I installed the 25mm Plossl (replacing the 25mm Ultrascopic). Wow, the hunch paid off. The filter revealed the airy disks of both the 2.0 and 2.8 magnitude components. There was no sign of the diffraction rings. Two distinctly separate stellar disks were seen, separated by the black of space. (Another good reason for the original investment.) To complete the test, I tried out the 15 and 10mm Ultrascopics in turn (without the filter). No success. At best I was only able to get a "dirty split" at 180X.
NOTE: While writing up my notes, I analyzed the Castor pair using the double star resolution calculator. It recommended 78X under fairly stable conditions to cleanly resolve this bright pair. I'll have to add a note suggesting that an OIII filter be used whenever two bright stars are targeted -- especially under poor conditions.
NOTE: Done!Despite the fact that the moon lay within 30 degrees (or so) of the Pleiades, I decided to turn the scope on it and begin to rough in a description. In anticipation of the characterization, I installed the 10mm (180X) ultrascopic and made a star count west of the Pleiades and later within the cluster itself. The numbers: 4-6 stars to the west and 8 - 16 within. Roughly then, the Pleiades are about twice as compacted with stars than their line of site stellar neighborhood.
NOTE: At 180X an average count of 5 stars in the FOV suggests that I was seeing stars down to magnitude 10.8 at the time. Since I had previously seen a 12th magnitude star at 120X it's apparent that the star count method is impacted in some way -- possibly by methodology, but more likely by the vast range in the number of stars seen throughout the sky. Still, I need to keep collecting these kinds of counts so I can improve the calculator over time and use...
The Pleiades themselves extend over a region well outside the one circular degree field of view of the 35mm Ultrascopic eyepiece. To offset this I reviewed the entire cluster followed by an on-the-fly decision to focus on a group of four 4+ magnitude stars oriented in a distended rectangle roughly around the east-west axis. These four stars provide the Pleiades with the "pan-shaped" region that gives it its mini-dipper shape. Preceding the pan, is a "prowshaped" group of dimmer stars leading it across the sky. Trailing this region is a pair of 5th magnitude stars that provide the handle. (Now all we need is the Milky Way to fill the pan.)
None of the half-dozen brighter stars "dominates" the cluster. However, the easternmost member of the distended rectangle does arrest the attention when scanning the cluster at lowest magnification available (50X). That star is preceded across the sky by a small (3X5 arc-minute) triangle of 7-9th magnitude stars. It is also encompassed by a larger triangle (some 20-25 arc-minutes in apparent length to a side) consisting of a dozen 7 to 10 magnitude stars. South of the "featured star", beginning near the apex of the outside triangle is an arc of a half-dozen 8th and 9th magnitude stars that curves back towards the east.
.
.
.
.
. *
.
* *.. . * west
* . *
. *
south
M45 Stars E-->W / N-->S: Atlas, Pleione, Alcyone, Merope, Maia, Electra, Calaeno
Magnitudes: 3.6, 5.1(variable), 2.86, 4.2, 3.9, 3.7, 5.4
NOTES: If you have 20/20 vision and can see all seven sisters,
sky transparency is quite good! Nebulosity associated with Merope
is the most susceptible (NGC1435). Next is that found with
Maia (NGC1432). (Don't forget Maia's name if you think you've seen it.)
Prepped with a sense of the basic layout of the cluster, I examined it again using the 25mm Plossl/OIII filter combination. Sweeping over the cluster I got the same sense of slight background changes in surface brightness seen during my Orion sweeps. Future observations of the Pleiades will probably focus on the barren region between the leading apex and small triangle of stars preceding the "feature star". The fact that this region is devoid of stars should help eliminate "star haze". The goal here will be to determine just what is causing this sense of low level variability in brightness. Meanwhile a detailed study of astro-photos is in order to determine exactly where nebulosity can actually be expected to be found.
NOTE: Photos of the Pleiades show nebulosity in association with all the brighter components (in asterisks above). If you've been following this observation series you may have noticed that it is difficult to distinguish between light scatter (star haze) and nebulosity in the presence of stars. The Pleiades should be an excellent region to explore methods to help make this distinction possible and apply it elsewhere (such as with NGC6888 in Cygnus).to: top of page
Just the Facts Ma'am
Date: Wednesday, February 7, 2001
| Type | Constellation | Magnitude | Size | Right Ascension | Declination | Total Stars | Brightest Stellar Magnitude |
| Open Cluster | Perseus | 8.4 | 10' | 3h 14m 44s | +47° 14' 52" | 200 | 11.2 |
I dedicated about an hour and a half to chasing NGC1245 down this evening. Couldn't be found. I wonder why?
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Can't Lose for Losing
Date: Sunday, February 11, 2001Sky over the Ridge was initially mixed. In looking off towards the beach (several miles to the south), a second, lower, line of hills can be seen between the Ridge and the ocean. To the south-southwest there's a break in the hills. The ocean itself can be made out in the distance. The sky above the ocean itself was quite transparent. A bank of clouds seemed to take form near the beach. This probably occurs where warmer air off the ocean makes its way over the land. The warm air cools rapidly and the clouds form. A light breeze from the southwest causes the clouds to progress towards where we stood. Even as we perused the scene it started to sprinkle. Then the rain came. The clouds obviously felt the need to free themselves of excess moisture. We packed the scope and headed home.
We took the long, more leisurely way back. Once we arrived, I looked up. The sky was clear and relatively dark. Despite this I had no great confidence in the prospect of a satisfying evening of observation. The clouds would be back. I set up the scope anyway. Iota Cassiopeia was just susceptible to the eye even within the worst part of the Boulder Creek lightdome. Overhead the transparency was in the 5.0 - 5.5 range. The Iota triple separated almost cleanly. Despite the split of Iota, Jupiter did not take 200X. At one point I made a quick check at 120X. Saw a large scale irregularity obtruding into the EB from the NEB. Pretty dramatic. Near the central meridian. Thought I could make out the split in the SEB. After several moments I resolved the NTB as well. Jupiter feature contrast is nice at 120X, but this magnification does not exploit the .8 arc-second resolution possible with this scope (under the best seeing conditions). (190X is the minimum magnification needed to accomplish this. 120X offers at best about 1.4 arc-second resolution.
Observations of Jupiter were incidental to what I had hoped to accomplish this evening. I made the check just to see if lower power offered any improvement in the contrast area. (An ongoing problem with this style scope.) My primary goal for the evening was to track down NGC1245. In addition I wanted to see if I could make out the 11.1 magnitude companion of Aldabaran. In fact I spent about 10 minutes inspecting the region around the star before switching to Jupiter. There is an 11th magnitude star near Aldabaran but it is about 1 arc-minute distant. The one I am looking for is separated by about half that. The other 11mag is a known field star. Aldabaran is moving away from its position at a fairly large rate. Due to the amount of light scatter around Aldabaran I was unable to make out the companion. I suspect it's going to require a warm dry night...One other check I made (using Aldabaran) this eveing has to do with a email discussion I'm having with fellow amateur astronomer Otto Piechewski. I was able to confirm that as magnification increases, the amount of off-axis elongation seen in extrafocal star images diminishes. This is no doubt due to the smaller field of view associated with higher powers. Ideally, off-axis extrafocal images would be identical to those seen on axis -- even at very low powers but since Otto's MK-67 also displays this phenomenon I'll have to accept it as a given. If there were some way to quantify this effect (aspect ratio of elongation at 30 arc-minute separation from center field of view for instance), the technique would prove invaluable for scope tests. Next star party I'll have to start making a few "discrete" inquiries.
About this time I could see that the next wave of low flying clouds was beginning to roll in off the mountains to the west. While the clouds passed I inspected Jupiter using the 25mm Ultrascopic and 9mm Plossl. The 25mm (120X) gives decent high contrast views but displays only the most obvious details. At 200X (using the 9mm) Jupiter wouldn't snap into focus.
The clouds thinned and Perseus stood out starkly in the 5.0+ ULTM region directly overhead. More clouds were approaching however. The gap wouldn't last long. In star hopping to the NGC1245 region using the 7X35mm finderscope, I was temporarily disoriented. There were far more stars in the FOV than when I last had an opportunity to search for it. (The moon had been a huge factor on preceding occasions.) Even as dark as it was, there was no perceptible open cluster "glow" in the finder. I was going to have to track this one down through the main tube. Unfortunately, I had only the 120mm ep. With its less than 30 arc-minute FOV, I could end up stumbling around for quite a while. I went inside and brought out the 35mm Ultrascopic. I began my search in the "B-shaped" aggregate just outside MEL20 (previously thought to be NGC1245). I shifted the FOV and thought I caught a glimpse of five or six 11+ magnitude stars inside a larger pentagon of brighter stars (near the foot of the "B"). Just as I caught site of this vague assemblage, low clouds moved in again. But these were thicker, and dripping with moisture. I packed the scope inside. And that was that.
The reality of 1245 is this. Unless conditions were much darker (say ULTM 6.5+) or I had a much larger scope (a ten inch) I would never have recognized such a small group of almost imperceptibly dim stars as an open cluster. Long exposure photos of this assemblage viewed on the web show it to be a very beautiful, tightly condensed pattern of stellar loops and circlets. Since, the brightest of its components begin at magnitude 11, I can only assume that the rest of the group falls in the magnitude 14-15 range.Despite not having really "found" 1245, the effort to track it down has been extremely valuable. Most amateurs think of "real deepsky" as comprised of distant globular clusters, diffuse planetaries, and, of course, far flung galaxies. Open clusters are usually though of as the stuff of small backyard telescopes. Many open clusters (think M45, M41, the Perseus Double Cluster etc.) are naked eye objects. Is it surprising that vast hordes of such stellar communities lie well beyond the reach of commonplace equipment? As such these assemblages are easily lost in the space between the spaces -- far removed from the better known regions of our own stellar neighborhood...
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Pretty Small for Gas Giants
Date: Monday, February 12, 2001It only happens every decade or so. Snow descends on the small town of Boulder Creek California. Big, huge fluttering flakes. Littering the ground and everything they touch with their pristine purity and soft, tranquil beauty. A great way to start the day. But would the day end with a sky equally littered with those radiantly lovely, distant cosmic snowflakes we call stars?
About 2:30 this afternoon I noticed that the sombre gray permiating my office through the window began to lighten up. At first it was only a subtle increase in luminosity. Then the familiar azure-tinted golden light of the sun interjected. Noticing this I turned away from my PC and rose in spirits to the possibility of a clear sky launching me into an evening's adventures. But as in most things, there is the differential and the integral of events. Would the promise hold or was this but a distant harbinger of that future day (and night) when the weather would finally break and I could resume February's "ambitious" observation schedule? A quick check of the "weather radar" on the web proved the latter. We were in the hollow, the eye, of a great swirling cyclonic low pressure system sweeping in moisture-laden air from hundreds of miles out in the Pacific Ocean and funneling much of it into Pacifica (aka Northern California). The weather would not hold -- but it might just last through the early evening.
As it turned out, the clouds abated until the sky got just dark enough to polish a few more facets of my observation plan. While waiting through dusk I made a few "equipment and technique" checks on Jupiter and Saturn. My first goal was to try lower magnifications on Jupiter. This plan evolved out of a 5 inch refractor "shootout" I had read about on the web. Strangely (to my thinking) the participants had settled on a magnification of 150X as giving the best view of Jupiter. (My own personal experience has been that, under steady sky conditions, 200X gives the best overall view in terms of sharpness of image versus wealth of detail.) I wanted to see if I had overlooked something...
As it turns out I possess two eyepieces which bracket this magnification. The 15mm Ultrascopic gives a boost of 120 diameters, while the 10mm Ultrascopic yields 180. The view through the 120X eyepiece this evening was fine for showing "macro-features" on the disk. (Macro features include the NTTB, the NTB, the NEB, SEB, the STB and general coloration effects associated with the SPR and NPR. (Occasionally, very large clots of material can also be seen obtruding into the EB even at 120X.) However, these same features are visible at 180X. In addition, 180X reveals a group of less difficult micro-features: NEB and SEB belt edge irregularities, SEB splitting (when present), small-scale intrusions into the EB and the GRS (again when present). Other, more subtle micro features are also possible but (with the possible exception of a quick look at Jupiter under exceptionally dry, clear, and steady skies at Fremont Peak), I do not normally view at this magnification. To be complete, this more subtle class of micro-features include: Belt edge irregularities in the NTB, festoons in the NEB, and "dove's footprints" within the EB. To be honest, I have yet to really inspect for this third class of details at 180X. Typically such things are observed at 210X using the 25mm/3X Ultrascopic barlow configuration. In that configuration I occasionally bump the magnification to 360X (using the 15mm in conjunction with the barlow lens) - at which point I usually see a more "bleached out" version of what is already visible at 210X. Finally a quick peek at 200X (9mm Plossl) did not improve on the image seen with the 10mm Ultrascopic. So to conclude this musing on the use of lower powers on Jupiter, I would say that, the optimum 150mm MCT magnification, under good (but not necessarily excellent) seeing conditions is in the neighborhood of 210X. Meanwhile under fair conditions (such as this evening) 180X gives the best view. Finally, when conditions really deteriorate, 120X is no doubt best. But keep in mind that as magnification is reduced to offset poor seeing the associated class of Jupiter detail is lost. (Conclusion subject to change without notice!)
So what comes out of all this is a new way to assess seeing conditions. Views of Jupiter that reveal steady fine detail (such as dove's footprints) probably support upwards of 360X on this scope. Under such conditions the stability of the sky is excellent (9/10). When conditions are very good (8/10), best views are probably at 220 - 280X. Here the subtle class of micro-detail comes in flashes -- causing you to tend to doubt your own eyes. Under 7/10 conditions 190X - 210X is probably best. There will be no flashes of superlative detail but the less-subtle class of micro-features are accessible through the scope. During 6/10 seeing, all macro features will be present (tonight, for instance) along with occasional flashes of the less subtle class of micro-features. You are then pretty much stuck with 180X. Finally, if you must drop to 150X or below, the seeing is only passable and macro-features are all you will be able to make out with any certainty. All this begs the ultimate question: If an MK-67 was in parking orbit around the Earth (instead of the HST) what magnification would be best?
A second issue of note regarding Jupiter is a phenomenon noticed by fellow amateur astronomer (and 150mm MCT afficionado) Otto Piechewski. Otto has noticed "unnatural" limb coloration effects. I've seen these too and thought they might be attributable to the eyepieces I use. Since Otto uses an entirely different type, I thought I'd take a moment to better characterize the issue. So while inspecting Jupiter using the 15mm and 10mm Ultrascopics (and 9mm Plossl) I determined that the planet edge that faced the center of the FOV took on an orange-red cast. The edge facing away displayed a bluish hue. Given the quality of the image seen tonight, it is not likely that the source of the problem is tube currents (as some have suggested) but simply a small amount of achromaticism (perhaps) associated with the refractive meniscus at the front of the scope.
I wrapped up this evenings series with a quick look at Saturn. The goal here was to determine "field flatness" by shifting Saturn around in the field of view and noticing where the image began to degrade while using various eyepieces. With the 35mm Ultrascopic in place, Saturn would only remain sharp in the center half of the field (roughly 30 arc-minutes in size). Outside this region the image could be corrected by refocusing -- but only up to about 2/3rds of the field (40 arc-minutes). After the 2/3rd's field mark, the image would not achieve focus at all. (It showed a large amount of intra/extra-focal astigmatism.) I then crossed my fingers and installed the 70mm Ultrascopic. The area of focus remained about the same (30 arc-minutes in diameter) and only near the edges did the astigmatism show up (close to 40 arc-minutes). Using the 15mm eyepiece (25 arc-minute field) only the very edge of the image lost focus. At 180X the entire field is flat (17 arc-minutes in diameter). I had seen enough. It is very likely that there is a problem with field flatness associated with my particular scope. (Edge astigmatism is probably attributable to the eyepieces themselves but the intermediate region is telling.) The only definitive thing I can do to shake out any remaining doubt is to try out a high quality eyepiece during a star party.
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Argo Gets a Sibling
Date: Wednesday, February 14, 2001It happened to me, not just once, but twice. Mom and Dad left on "urgent" business. They returned (several hours later) bearing "a little bundle". In my case it was two younger brothers. In Argo's case, "The Little Bundle" was a "Made in China" Orion Shortube 80mm Achromatic Refractor. -- The stork came a long way. And, Argo was no longer the sole illuminator of the Barbour Family night sky.
All of this happened yesterday. But, as might be expected, other than assembling the telescope and mount (without looking at the directions I might add -- both son Eric and I are male.) We were all dressed up with no place to go. The "new telescope curse" struck again. The weather allowed for an only one diffuse glimpse of a cloud-faced Jupiter.
This evening was only slightly different. We got one half of a glorious hour between 6:30 and 7:00, and another more typical not so glorious half-hour between 7:30 and 8:00. Again the sky was less than fully supportive of our enthusiasm. However, during that combined hour we had a chance to turn both Argo and the Pup on Jupiter and make a quick compare. Followed by a quick series of easily located shallow and deepsky objects for the Pup alone. But it all started with the usual assessment of conditions using Argo.
The triple split of Iota Cassiopeia was very clean this evening. Nice diffraction rings visible surrounding the 4th magnitude primary. Clear space visible between both the 2.5 and 7 arc-second companions. But this was using the MCT. A 500mm focal length 80mm scope (such as the Pup) would have to work very hard to create any space between the tighter pair at all. I didn't even make the effort. Jupiter was closing in on the tree tops. The Pups Iota split attempt can wait another night. (Hopefully tomorrow!)
Even with the sky not quite dark, the 12th magnitude field star could just be held at 180X (in both the 10mm Kelner and the 9mm Plossl). With Iota split so nicely I knew Jupiter would be a superb sight. No disappointment here. At 180X (Kellner) and 200X (Plossl) all the macro and a few of the less subtle micro features were present. Eric and a friend took a peek. Both were impressed. The limb of the planet was sharp and clean against the black of space (especially in the Kellner). Sharpness across the entire body was superb. Contrast between the two equatorial belts and the equatorial band was unusually good (again especially in the Kellner).
Could the Pup do half as well? Well, to be honest, not even close... With the 3X barlow 9mm Plossl combination (156X), the best I could make out were the two EBs and a hint of the NTB. No belt frontier irregularities, no NTTB, certainly no SEB belt splitting and no STB. I could see some exceptional colors on the limb of the planet though. Green and violet to be precise -- chromatic aberration.
Well enough on Jupiter. We already have a good planetary scope. The Pups for something else: "Rich Field" views of star fields, open clusters, and nebula. Using the 25mm Plossl the thing sucks in almost 3 degrees of the sky at a time. It swallowed the entire Pleiades and left room for several M42's to boot! In fact, with the OIII filter installed, real nebulosity (not star haze or imaginosity) could be seen near all of M45's brighter stars. Later, (just before the clouds rolled in), that same magnification gave an excellent sense of the location of NGC1245 in Perseus. (The 3" showed a diminuitive "light mound" near the B asterism originally confused with 1245 during an earlier search.) Even as the sky began to cloud over, the Pup was still able to reveal M42, M43, and split the Trapezium into it's four brightest components. (The 8th magnitude component was just visible however.) Chromatic abberration, as seen on Jupiter's limb, was not an issue when viewing the dimmer objects of shallow and deepsky.
As a test of magnitudinal reach, I also took a look at Aldabaran. The 11.2 magnitude come (some 1 arc-minute distant) could just be caught with averted vision at 20X. (The scope should directly peer down to magnitude 11.3 under 6.0ULTM at this magnification -- absent the overpowering influence of a bright star such as Aldabaran. In fact there are at least 40 DSO's it should give optimal views of.)
Despite the glowing things I seem to be saying about the Pup. It is a marginal scope as a whole. The optics are rather poorly color-corrected. The finderscope has a bad memory for alignment, and doesn't focus properly if you go without eyeglasses. The equatorial mount has limited right ascension knob adjustment travel. There is very little flex in each of the cables that provide slow motion control. And grease will gladly line the palm of your hand if you are careless with the helical focuser. Did I leave anything out?
But for three hundred bucks whose complaining?
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Finding a Lost Sheep
Date: Thursday, February, 15, 2001The drive up to the Ridge was unusually squirrelly this evening. The recent snowfall downed numerous small trees. Branches bearing fresh green leaves protruded out at odd-angles onto the pavement from the roadside. Potholes made like rabbits, more of them all the time and. like those in Australia, lacking natural predators. We drove along like cautious open-field runners then darted like the field mice that occasionally errupted from the undergrowth. First left, then right, surge ahead, then slow just long enough to pick the best line through the detritus.
Earlier we had packed Argo and the Pup into the hatchback of the Civic. My hope was to get enough of a reprieve from the relentlessly variable sky to capture a decent look at spiral galaxy NGC1300 in Eridanus, plus follow up on the "light mound" in Perseus (whose position had been suggested by the Pup the evening before). Eric was looking forward to a chance to be "captain of his own scope, master of his own charts". (In other words, Eric had no particular plans about what to look at and wanted to be open to the inspiration of the moment.)
After arriving on site, it took us a while to sort out all the equipment we had with us. Assembly was interrupted by the occasional lost fasterner. Fortunately the flashlight aided speedy recovery. Both scopes were on their stands and ready, just as the sky darkened. I turned Argo on Jupiter using the 25mm Kellner / 3x barlow combination. Stability was very good. Despite high thin clouds, Jupiter gave an excellent view. As it turned out, I didn't have the opportunity to really adapt my eyes to the point where I could check for the subtlest class of features (dove's footprints in the EB and intra-equatorial belt festoons).
Eric was far more familiar with operating Argo than the Pup. Although the Pup rides on a german equatorial mount / tripod combination, it took a little orientation to get him comfortable with it. In addition the uneveness of the ground required we adjust the lengths of the various tripod legs to get it to align with Polaris. All of this was complicated by the futility of relying on the miscreant finderscope. (Eric and I decided that it has to go. The barrel of the scope plus 19X ep is satifactory for acquiring what you want to see.)
By now the sky was getting dark enough to pursue NGC1300. I consulted my star charts and determined that the best way to begin was to draw an imaginary line from Alpha Ari, through Delta Ceti. Double the distance then start tri-angulating north of Tau 4&5 Eridani. Turning to the sky (after working this out) I saw the clouds begin to dominate the very region I would searching in. Who'd a guessed it?
While I re-oriented Argo on Perseus, Eric began his explorations of Orion. (No idea why he would want to start in that obscure part of the sky...) In one 19X 3 degree field, the Pup could squeeze in, Zeta, Theta, and Sigma Orionis plus attendant nebulosity. After centering the FOV on Theta, I challenged him to tell me how many stars he could see in the tight group emersed in the nebulosity of M42.
While Eric did his star count, I turned Argo on the suspected NGC1245 region. That region of the sky probably revealed stars down to magnitude 4.5 unaided. (High thin clouds were taking their toll on the transparency.) The 7X35mm finderscope revealed nothing "small cluster-like" in the region. I inserted the 50X 35mm Ultrascopic and began searching for "a sprinkle of 11th magnitude stars in a hazy field". I noticed a 15 arc-minute sized keystone of stars that looked suspiciously like what I had seen in photos. Near the southern corner of the keystone, scintillation of two or three 11+ magnitude stars appeared. Switching to 120X (15mm Ultrascopic) I could directly acquire perhaps three of the stars. I could also make out the scintillation of perhaps a dozen others (as I flitted my eyes across the FOV). What a pleasant passtime. Look at one star directly. It promptly disappears as three or four others appear. Magical! I like this cluster. I think I'll have to visit more often, if only the weather would cooperate.
Now back to the dry stuff: "NGC1245, 12 to 15 stars visible with averted vision (using a 150mm scope at 120X on a 4.5 ULTM night). Visible components arrayed over a region perhaps 8 arc-minutes in length by 4 arc-minutes wide. Swath of 11.5+ magnitude stars oriented along the east-northeast to west-southwest axis. Under similar conditions the cluster needs at least 250mm aperture to plainly reveal it's dense open cluster persona. Needs to be revisited under 6.0+ dark sky conditions for similar view using 150mm..." I'll have to amend the star cluster components of the the surface brightness calculator based on this observation. Cluster of magnitude 8.4 (integrated) and 10 arc-minute size should be optimized for a 200mm scope not a 250...
Eric's Comments: I love being captain of my own starship. There's a surprising difference between searching on your own and being copilot of another telescope. I chose to start on Orion because the Warrior figure has always interested me. And because for the previous few minutes I had been studying Orion with my eyes and decided to take a closer look. Exploring Orion's belt, sword, and bow, I found a "V" of bright stars around (Zeta) at 19X. Later in looking at the sword, I saw four stars that were very close together (the Trapezium) at high power (44X). Originally, I could only see three of the stars but while glancing to the scenery around them I accidentally caught the fourth from the side of my eye.to: top of page
Anatomy of a Tough Catch
Date: Friday, February 16, 2001Arriving in Watsonville we exited onto Airport Drive then caught a major road heading south (which bisected the commercial district). We stopped for a pair of veggie burritos, exchanged a few words of common espangol with the staff and resumed our drive. The run along HWY 129 west was equally pleasant. There were excellent views of various flat-topped intra-coastal peaks. These presented themselves during various twistings and turnings in the road. The town of San Juan Bautista soon sprung up in the windshield. Much quicker, I might add, than my last (and first) drive out. Soon we were wending our way along the ten mile run up to the park, the peak, and the favored observing site just below the campgrounds.
The plan was to put in as late an evening of observation as possible, then crash until morning. As it turned out "long as possible" proved to be about an hour and a half. This lead to our early return home and the comfort of our own beds. But not without a few excellent views of Orion seen through the 80mm Orion Shorttube (at 16 and 44X). And the opportunity to determine if the 10.4 magnitude 7X4 arc-minute face on barred spiral NGC1300 in Eridanus would be susceptible to Argo under less than optimal conditions.
Well, how were conditions (you might ask)? "Umm" says I, "fair to begin, and downhill from there." By 8:30 Lambda Orionis (magnitude 3.7) was barely perceptible direct and even our copious enthusiasm for observation flagged to the point of an early exit. Previously, and just after astronomical dusk, the sky was streaked by occasional high thin clouds but even so blue sky prevailed (not without obvious signs of high water vapor). At that time a good estimate of zenith conditions would be roughly 4.5ULTM. However, my observations were to the south (and progressively more west) where the only star visible (nearby) was Gamma Eridanus (magnitude 3.2). The region NGC1300 itself occupies was also rapidly entering an expanding light dome emitted by Salinas to the southwest. That dome efficiently reflected back down to us by mounting high thin clouds and the ubiquitous atmospheric water vapor.
So to be technical, and by the numbers: At 30 degrees above proximate horizon, bearing a published integrated magnitude of 10.4 spread over a 7X4 arc-minute region of space, NGC1300 has an average 1 arc-minute surface brightness of 14.1 magnitudes. Since it is a "spiral galaxy" it is presumed to have a bright core and therefore a peak surface luminosity of roughly of 12.1, (this again over a single arc-minute of apparent angular displacement). At 50X (~35mm Ultrascopic in my 1800mm fl MK-67) the susceptibility magnitude (of the core region) is approximately 11.8. This means to view it directly and fix it with perception Argo had to be able to reveal stars of nearly the 12th magnitude in a rather poorly positioned region of the sky, on an equally poor night of low transparency.
Again, to be equally technical and by the numbers: At 50X, Argo can add 6.8 magnitudes to the ULTM. This night, at its best, and at the zenith, Argo could probably directly reveal stars of magnitude 11.2. Without the light dome from Salinas, the area of the sky 30 degrees above the horizon would possess an ULTM of magnitude 4.0. Thus Argo could peer down to magnitude 10.8. Since averted vision can reveal objects roughly 1 magnitude dimmer than those held directly, I would expected the following scenario to play out while attempting to turn up NGC1300:
First locate Alpha Ari and Gamma Ceti by eye. Draw an imaginary line between the two stars and extend that line the same distance to the south toward Eridanus. Align the main tube so that it points directly at the terminus of the line. Peak through the finderscope. Look for a wide optical double consisting of a 4th (Tau4) and 5th magnitude star (SAO168452) oriented roughly north-south and separated by about one degree of arc. Swing the scope 4 degrees east and verify a second 5th magnitude star slightly north of the arc (Tau5). (This verifies you actually found Tau4.) Then swing back to Tau4. Slew the declination straight north 4 degrees. Notice a second wide pair of 5th and 6th magnitude stars. Center the dimmer star of the pair in the FOV. Return 1 50X ep fieldwidth south. Look for a small (3-5 arc-minute) light mound out of the corner of your eye. Center that object in the FOV. Look directly at it.
It will disappear.
Congratulations you found a 10.4 integrated magnitude object smeared over a region of about 25 arc-minutes whose brightest point appears magnitude 11.8 on a night when your scope can only see down to magnitude 10.8 at the zenith in a part of the sky where 4th magnitude stars require a finderscope to make them obvious while thin clouds begin to throw down light from a small city 10 miles to the southwest.
Does any of this make any sense?
Well that's what happened. I found it and I didn't. Whatever it was lacked shape, size, or any perceptible detail. It was just simply slightly brighter than the sky around it -- but only when I wasn't looking at it. Kind of a shy creature of the night. Perhaps on a finer evening, when it can be truly appreciated, it will come out with a little more confidence and allow me to see it as it truly can be in a 150mm telescope -- a roundish patch of light bearing no particular orientation, maybe 4 arc-minutes in diameter in the presence of 3 or 4 tenth magnitude stars forming a rough trianle around it.
Oh, BTW: Eric and I got some nice views of the Orion sword region through the 80mm Pup. During peak darkness (around 7:30) the amount of M42 visible in the 9mm Plossl ep (at 44X without OIII filter) surprised even myself. Once again, if I haven't already said it, amateur astronomy comes down to four things: a dark stable sky, good optics, proper magnification, and appropriate object selection. Consider, for example, a view of Cygnus the Swan, on a warm dry autumn evening with the cross placed high overhead, no moon, from a rural mountain top, viewed by a set of eyes correct to 20/20 vision. Why, is that the North American Nebula?
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To Beat the Weather
Date: Thursday, February 22, 2001So, I went south. As far south as I could get. As far south as the traffic and the late hour would bear. As far south as was needed to reveal something of a clear sky. How far south? Not south enough.
Around 6:30 I pulled into the parking lot of Manressa State Park half-a-dozen miles south of Santa Cruz, CA. The park butts up against the beach looking south over Monterrey Bay. The Park-ing lot did not speak to me. So I moved on. A mile down the road I pulled off onto a private road. Just off the road was a large graded patch of earth. Several large mounds of clean fill were distributed over the patch. I set up the scope behind the nearest mound. It offered some protection from the moderately gusty wind blowing off the bay from the south. I could hear the ocean crash in the distance. Silent Jupiter could just be picked out in the darkening sky overhead.
Even as I positioned the mount and added the slow motion controls, I could see the clouds rimming round about the site. I could only hope that I could somehow find a way to work around them to advance my now tardy observing plan. It was still too early to make any attempts on the deepsky. I took a stab at aligning the axis of the scope to the north and pulled Jupiter into the 180X 10mm Ultrascopic field of view.The sky around Jupiter was still "blue". All four Galileans were present. Io was fast approaching the trailing (terrestrially eastern) portion of the planet's limb. Within a few moments the satellite took the plunge and attached itself. I watched it progress inward passing totally within Jupiter's variagated globe. Despite the ingression, it remained clearly discenrable along the southern termination of the south equatorial belt (SEB).
The SEB itself was clearly split. The flanking components sandwiched a lighter region in their midst. Facing the SEB, the north equatorial belt (NEB) displayed a large clot of material. The clot ingressed into the equatorial band leading Io perhaps 1/3rd the way across the disk. Paralleling the NEB was a clearly discernable north temperate belt (NTB) and a less obvious but still recognizable north north temperate belt (NNTB). On the far side of the globe (to the south) the corresponding STB was detectable - but not in it's entirety. The southern flank of the STB blended into the south polar region (SPR) and the part of the belt that leads the rest across the planets limb (to the terrestrial east) was missing. Both the SPR and NPR lacked the occasional mottling seen under the best seeing conditions. Despite the steadyness, there was just too much residual light in the Earth's atmosphere to reveal this kind of detail.
By this time I was beginning to get a little claustrophobic. Clouds were starting to put the squeeze on the sky - and by extension - on me. The sky was quite stable. I wanted to view Jupiter at 360X and perhaps coax a little more detail out of the equatorial belts. This would require engaging the clock drive. To do this precious observing time would be sacrificed waiting for the Earth's rotation to carry Jupiter into the field of view before I could engage the drive motor.
I locked in the drive and while waiting for Jupiter to enter the FOV, assembled the 3X barlow / 15mm Ultrascopic combination. The race was on. The sky was deteriorating. Jupiter was still several degrees from the finderscope crosshairs. Everything was in place but...
The weather.
Just as Jupiter enterred the field the clouds thickened. I remember catching only a quick, low contrast glimpse of the clot on the NEB, and no sign of Io just before the planet was fully obscured. Over the next hour, I caught an occasional glimpse of His Majesty. But He was never entirely free of his cloudy mantle. There would be no new revelations this evening...
I started putting away my equipment - at a leisurely pace. I looked up. Orion peeked through the clouds. Popped the 25mm in for a quick look at the sword region. The clouds bested me. By the time I slewed the scope into position, the clouds would swallow him up again. Chuckling to myself I thought, "When you finally do give me a good night I'm going to enjoy it all the more for the games you've been playing."
Just as everything was packed up safely in the hatchback, I felt the first few drops of an incipient shower. "Most considerate of you. You know, this could be the beginning of a beautiful relationship".
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Weather or Not, That is the Question
Date: Monday February 26, 2001Yesterday afternoon I consulted the NOAA GOES image for the Western CONUS region. A wedge of clear sky was edging down from the north. So around 5:30 I headed up to the Ridge and enjoyed the view as clouds moved in from the south. Made a quick run up to Skyline Park (west of Palo Alto, altitude perhaps 2.5 K feet). Found that the Park closes at sunset - and most importantly the docent locks the gate. Noticed a lot of fine overlooks along HWY9 north and a few on Skyline Drive as well. All of the above noted for future reference.
Today I pulled up another GOES image. The entire combined Monterrey and San Francisco Bay Area showed indications that it would remain completely socked in with clouds. So I made no special effort to travel with the scope. Again, for the second day in a row, the sky made a lie of the satellite image. The sky cleared up quite a bit. Although intermittent low clouds and continuous high thin ones wrecked havoc with transparency, nonetheless there be stars in that their sky.
Pulled out the 150. Decided to dwell on Jupiter and Saturn a bit. (The sky wasn't that transparent over Boulder Creek, and I'm pretty much restricted to the Zenith over my backyard. The view south is blocked by trees. The view north is polluted by downtown lighting.)
Earlier in the day I had read a report by fellow amateur astronomer Otto Piechewski. Otto raised some concerns about discerning Saturn's Crepe Ring (Ring C) and the Encke Minima in Ring A. I had pledged to follow up on my own (guarded) reports of being able to make out these subtle features of the ring system. By the end of tonights observing session I remained "guardedly optimistic". Yes the Crepe ring (at least the part of it that adjoins Ring B) is visible (as a dark grey extension) from the interior of Ring B. Meanwhile, I also confirmed that the Encke Minima can just be caught -- under moments of exception atmospheric stability -- with slightly averted vision. (During those few occasions when excellent transparency and stability have occured I may have been able to hold the Encke Minima directly at 360 - 540X.)
Meanwhile, I took advantage of tonight's good to excellent stability to view Jupiter under a variety of magnifications using the Kellner 25 and 10mm eps and the Ultrascopic 15mm. (Magnifications: 180, 210, 360 and 540X.) In so doing I shored up insights already made regarding the eps in question and the types of features you would make out at the various magnifications. Basically, the 3 element kellners provide slightly better image contrast than the 5 element Ultrascopics. However, the Ultrascopics have a slightly wilder field of view and better ghost suppression. The Kellners were also almost perfectly parfocal with the Ultrascopics while the Plossls used previously are not. So the Plossels are being re-assigned to the Pup (80mm Orion ShortTube) while the Kellners are now to be used by Argo on the planets. (The Ultras own deepsky.)
In terms of Jupiter features, 180X Kellner and 210X Kellner-Ultrascopic Barlow views showed all the basic macro features (NNTB, NTB, NEB, SEB and STB) plus some of the micro feature set (SEB split and a hint of xEB edge irregularities.) By bumping to 360X, the 15mm Ultrascopic / Barlow combination, made the edge irregularities much more obvious. Details within the two equatorial belts were also enhanced. These included the GRS embedded within the SEB, a thin line of darker material (at the western edge) bisecting the equatorial band and hints of textures within the EB (dove's footprints). However, the additional magnification seemed to "wash out" the NNTB and the STB. So all in all, it makes sense to say that -- while exploring Jupiter -- macro features should be viewed at 200X and when conditions permit zoom to 360 + magnification to get a handle on details associated with the Equatorial Belt region. (BTW: The 540X view using Kellner/Ultra barlow combination this evening was better than I had ever seen it --in terms of contrast-- while using the 10mm Ultrascopic/barlow combination. This raises the hope that "quarter-dollar" sized images of Jupiter may actually prove beneficial under extremely dark sky/high stability conditions.)
While viewing Jupiter, I saw one of the satellites egress from the STB region of the planet (around 7:30 PST). This is a first for me since, to this point, I have only seen Io (and possibly Europa) pass along the SEB. Curiously, no shadow was visible on the body of the planet before the egression. (Although I often saw dark satellite-shadowlike "spots" on both the NEB and the SEB this evening.)
NOTE: Later I did some research on the web and found a nice little applet on Akhana Peck's site. The applet revealed, based on the above time and date that it was Ganymede that had transited. As it did so, Ganymede's extremely southern trajectory (relative to the Sun) failed to cast a shadow on the globe of Jupiter.
Currently I have two "most wanted" warrants active. Both relate to double-stars. One, Omicron Persi, is a magnitudinally disparate pair separated by a single arc-second. The other is Aldebaran whose 32 arc-second companion is of the 11th magnitude and will require a darker night than this to make out. (Although a second 11.2 magnitude come was directly held roughly 2 arc-minute's distant using the 180X 10mm Kellner.) In checking Aldebaran I thought I caught a brief glimpse of a dim star due south of the 1st magnitude primary. I installed the OIII filter on the 10mm Kellner for my Omicron check. As expected the filter reduced the spurious image size of the 3.9 magnitude primary considerably, but the two magnitudes lost to the filter failed to reveal the 8.9 magnitude secondary. (The Kellner could probably reveal stars down to magnitude 11.0 this evening in the direction of Omicron. The filter drops two stellar magnitudes - so the companion would have been right on the magnitude threshold.)
I transferred the filter to the 25mm Kellner and made a quick inspection of the Pleiades (for nebulosity). There was plenty of glow around many of the brighter components but nothing definitive. This could be nebulosity or it could be sky haze -- who knows? (Where's the Shadow when you need him?)
Got hugely motivated to find at least one "first light" this evening. Given the fact that Perseus was losing ground to light pollution north and west, I went after an open cluster in Taurus (NGC1647). 1647 was actually quite easy to turn up. Since I use an equatorial mount, I can get pretty accurate tracking north and south (declination) and east-west (right ascension). 1647 happens to be due east of Epsilon Tauri (about 5 degrees). All I need do was center on Epsilon (not far from Aldebaran) and slew east. Imagine how amazed I was when this little bit of telescopic legerdemain actually worked!
There it was: 50-60 stars magnitudes 8 through 11. Rough s-shaped backbone of brighter stars oriented north-south. 7th magnitude blue-while field star to the south. Several star pairs, most separated by a few arc-minutes. Rough triangle of 9th and 10th magnitude stars to the west gave the sense of "a spinning top". The spinning seemed to throw off other more scattered stars within the 40 arc-minute cluster. As such, NGC1647 is a "dynamic" cluster (like the ET cluster in Cassiopeia which seems to flap its wings in an attempt to "fly home".)
Well there you have it. The weather giveth and it taketh away. There's no absolute way of divining the skies many moods and possibilities either by looking at satellite images or by consulting experts. The weather is as the weather does. It is large and it is in charge. Take advantage when you can.
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Back in the Saddle
Date: Tuesday, February 27, 2001All indications were that the sky would be extraordinary clear and dry this evening. There was no need to consult visible light satellite images, the local meteoroligist, or the entrails of pidgeons. Woke up, looked out the window, and watched a few faint fluffies float lazily overhead. By lunch time the sky was brilliant, vital, and almost unblemished in its blueness. I cut out of work early (with a promise to make up for lost time later in the week). Layed the equipment out on the back deck to drive off condensation, repacked everything (once warm to the touch), and headed up to the Ridge. The idea was to catch the moon at sunset, move on to Jupiter and Saturn (before full darkness) then to several much-delayed DSO's from my observing plan.
In viewing the moon, I became aware that it is extraordinary on every scale of perception. Anyone with reasonably well corrected vision can make out the smooth, basin-like "seas" (maria) along with the brighter, rough-looking plains that rise above and encompass them. Almost any kind of optical aid (such as a 7X35mm finderscope) brings out huge differences in contrast between plain and maria. While waxing or waning, the moon's dark terminator can be seen as a broken line dividing the globe irregularly north and south. Meanwhile, the cause of the irregularities can be traced to the uneven, broken surface of the high plains through which the terminator largely passes. When viewed through the main tube, the moon is overwhelming with extraordinary detail. Maria are seen to be less than the perfectly smooth surfaces they appear to be at first glance. Craters, both moderately sized and small ruffle the smooth surfaces of the maria, like waves frozen in the moment of creation. Surrounding the maria, jagged mountainous peaks abruptly loom. In some cases peaks spill over into the "seas". Such incursions are especially well seen when the maria are close to the moon's terminator. For it is near the terminator that the sun's radiance is most aptly collected by one-half of the vertiginous peaks. The peaks, in turn, cast hugely exaggerated shadows across the lunascape. Yes, the moon is extraordinary in richness and complexity. But it is that very complexity which some of us amateur astronomers find so intimidating. For you see, the moon is a specialists dream and a generalists nightmare. Selenography demands a huge investment of time and research. Endless is the lexicon of features that may be resolved in even the most humble astronomical scope. It is, as has been aptly said by others, "The study of a lifetime."
Now were it possible for the main instrument to show as much planetary detail as the finderscope reveals of the moon! Even that most detailed of planets, Jupiter, as seen through a 150mm telescope at 210X, pales in comparison with the view of our own moon at 7X through a 35mm achromatic refractor. Jupiter's features are all too easily lost to atmospheric instability or high clouds. Even under the best circumstances, it takes great visual acuity and extended patient effort to make out even a small portion of the wealth of detail that Jupiter possesses. Should the average amateur telescope be placed in orbit around the Earth, it is unlikely that the view of Jupiter could compete with that of our moon through a finderscope on the surface. But it is this very fact of Jupiter's ambiguity that makes it such an interesting study. Jupiter, unlike our moon, is alive with dynamic forces and possibilities. Hovering on the limit of telescopic perception, is a world spinning with utmost rapidity. Vast corriolus forces drive a tremendous atmospheric engine of change. Features on and in that atmosphere perch right on the border between stability and chaos. Those of us who follow Jupiter regularly never feel either overwhelmed by too much rigid detail, or hopelessly frustrated by veils of inscutability.
If the ambiguities of Jupiter do prove frustrating on occasion, the amateur can turn to Saturn for solace. Under clear, steady skies Saturn is crystalline in the fineness of its presentation. With the ring system arrayed in full splendour (as it has been for the past six months of my experience) the main ring division (Cassini's) remains sharply etched around the entire visible portion of the system. This alone is enough to restore one's hope that such clarity of detail remain's possible for the other planets. But Saturn too has it's ambiguities. The ring system, the planets main belt, and its rather extensive polar regions all possess a sense of undecipherable texture. Outside of the unmistakable Cassini division, to view Saturn is to see a great deal of detail without really seeing anything describable at all. Saturn as a whole is detail, it would be needless for it to compete with any one of it's parts.
Having appraised the moon and planets, astronomical dusk approached. Orion hung well up in the south southeast. I had two very difficult objects on my observing list that actually needed attention several weeks back. One, NGC1851, was a compact 7th magnitude globular cluster in the obscure southern constellation of Columbo the Dove. The brightest star in Columbo is of the 3rd magnitude. It was just possible to make it our some twenty degrees above the southern horizon. But to know that this star Alpha Columbae was what I thought it was, would take some celestial geometry. First find Delta Orioni (the northermost member of the Sword of Orion). Then locate Alpha Lepori (the northermost star at the center of the Leporian "butterfly" -- just to Orion's south). Extend a line from Delta Orioni to Alpha Lepori and double its length. This confirms the location of Alpha Columbae. Center Alpha in the finder then swing two degrees south and west to center on Epsilon Columbae. Continue to slew the scope another six degrees due west until an optical double enters the field (Gamma Caeli). Half split the distance between Epsilon and Gamma and slew the scope due south another 6 degrees. Carefully inspect the finder for a dim out of focus star. Center the finder and inspect the main tube. There it is a, a surprisingly bright and remarkably compact globular cluster -- NGC1851.
1851 is about one magnitude brighter than nearby M79 (which lies almost 15 degrees due north in Lepus). 1851 is also much more compact, displaying an almost brilliant star-like core that easily rejects all efforts at resolution. The remainder of the globular quickly falls way in brightness. In fact, even at 120X, I could only make out a little more than half the globular's 11 arc-minute size. There did appear to be a bit of roughness about 1851's surface. (But no more than what can be seen in the core of any bright galaxy -- such as M31.) No sign of the usual globular elongation (caused by the powerful tidal forces at work in the core of the Milky Way Galaxy). The cluster does not share the spotlight with any close, bright line of sight stars. However, a 9th magnitude field star can be seen about 15 arc-minutes south of the cluster. The cluster's core appeared slightly brighter than the field star. I suspect that observer's in the southern hemisphere look forward to the seasonal opportunity to view NGC1851. Those with large dobs probably strain at the eyepiece in an attempt to catch individual stars across the core.
Confidence gained finding 1851 should have provided a leg up on my next target. But even the dark sky conditions of this evening (as opposed to the wash out effect of the Salinas light dome in my last attempt to find NGC1300 at Fremont Peak) was no guarantee of success. In fact, despite the fact that I could unaidedly make out the bulk of the Tau series of stars in Eridanus (magnitudes 4.0 - 4.5), I had no luck in definitively finding 1300. Part of this may have been due to the rather cavalier instructions of one authority ("1 degree south" of a certain pair of 6th and 7th magnitude field stars) but another part of it is due to the fact that, at magnitude 10.5, extended over a region of 7X4 arc-minutes, placed some 30 degrees above the horizon, the adjusted surface brightness of NGC1300 requires a 150mm telescope just to find the core -- which is probably what I did, in fact, find. So my best stab at NGC1300 was located some 20 arc-minutes due south of the dimmer (7th magnitude) component of the pair of stars alluded to above. What I caught was a dim, 11th magnitude " fuzzy star" displaying a hint of irregular surrounding nebulosity that could, however, be directly held by the eye at 120X. About all one could expect to find under the circumstances.
My next "first light" deepsky object was a planetary nebula located near Perseus. NGC1514 is located about 1 degree south and 3 degrees east of Zeta Persi. Given how "easy" this loaction was for me to find, I decided to try out my setting circles. To do so, I centered Zeta in the main tube and estimated its RA and declination values from charts. I set the circles to the estimated value (just for the experience) then simply repositioned the scope by offseting it by the required amounts on both axis. (Note I really didn't need to calibrate my circles to Zeta, I could have simply zeroed them out, and used them relatively -- as opposed to absolutely.) I also took the precaution of installing the OIII filter on the 70X 25mm ep since large (2 arc-minute diameter) 10th magnitude planetaries can be quite difficult - especially when accompanied by a bright central star.
NOTE: I failed to note in my original report, that, while observing NGC1514, I got a distinct impression of "yellowishness" about it's nebulosity. This was not something I literally saw -- only an intuitive sense.
As it turned out the central star was quite bright (probably around magnitude 8). Fortunately, the star was part of a "shopping cart" asterism made up of about 5 8th and 9th magnitude stars. (The asterism orients east-west and takes up most of the 40 arc-minute field of view, 1514's central star is the right rear "wheel" of the cart.) The other stars of the asterism, though of similar brightness, didn't show nearly as much "star haze" as 1514. However, had I not chose to use the OIII filter, locating this planetary would have been far more difficult, since without the filter, the surrounding nebulosity was only marginally brighter than the haze around it's neighbors and was exceedingly circular in appearance. A potent recipe for easy dismissal as garden variety haze when not paying close attention.
Inpecting 1514 showed no obvious sign of a ringlike center or rigid annular frontier. Nebulosity completely surrounds and subtley engulfs the primary. No visible gaps were apparent, nor was the frontier particularly well defined. A more experienced eye than mine would probably take exception to this meagre description, but so be it. Future viewings of 1514, by myself and others, will probably reveal more -- even through smaller scopes.
Before packing everything up I just had to take a quick peek at M42. Magnificent!
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A Trio of Stellar Communities
Date: Wednesday, February 28, 2001The weather of the last few weeks has definitely placed me in catch up mode. Certainly, many of February's offerings can be pushed back into March. But I'd like to keep the backlog as low as possible. So this evening, despite other commitments, I took the scope out to track down a trio of open clusters in Perseus.
The first cluster (NGC1513), proved far too elusive for the regional 4.5 ULTM (Perseus is now positioned within the Boulder Creek lightdome). After checking and double-checking the charts, I abandoned this particular quest in favor of better conditions at a later date. Certainly discretion is the better part of abject bull-headed determination. As it was, I spent half my observing time attempting to turn this one up. With all this said, the reality is that I may have actually caught 1513 as a faint sprinkling of 12 plus magnitude stars about halfway between Lambda and Mu Persi. However, nothing definitive. This particular object is almost half a magnitude dimmer, and slightly larger than, NGC1245. It's magnitude and apparent size gives it a super low average surface brightness. It will probably take a regionally 5.5 night to confirm its position. But even under such conditions, very little of its dense open cluster nature will reveal itself. For now I am content that I've familiarized myself with NGC1513's neighborhood...
Of the three clusters, the next (NGC1528) is the most "cluster like". Some fifty 8 to 12 magnitude stars were easily acquired. The cluster took up about 80% of the 120X field of view. As such, it displaces more than 15 arc-minutes of apparent field. 1528's brightest stars array rather elegantly in two interwoven, but distinctively different, patterns. The outer pattern is quite geometrical (triangular). This triangle encompasses a more looping and arch-like "M-shaped" group of stars slightly to the west. The base of the outer triangle is positioned to the east. Its tip leads the cluster across the sky. The M-shaped arc orients roughly north-south. The end-points of its curves also point west. Unlike other open clusters, there was no sense of "pairing up" between stars. Juxtaposed behind the two patterns is a nebulous swarm of 13 and dimmer magnitude stars. Flitting the eye over this backdrop revealed a subtle scintillation. The effect however, is not as strong as experienced with NGC1245. (1528 has a large number of clearly perceptible stars to capture the attention.)
NGC1545 was the evening's final cluster. It too displays an unusual combination of elements. Its western component consists of slightly less than a dozen 8-10th magnitude stars. The general shape of this group suggests a chimpanzee with arms raised in "ape-hangar" position. Above the chimps "head" is an oblate group of perhaps a dozen 12th magnitude stars. This group is reinforced by a dense, nebulous field of even dimmer stars. This second group looks so different to me that I personally believe the brighter stars are line of sight -- not part of the actual cluster. Since, however, it has been assigned a cumulative magnitude of 6.2 (even brighter than that of NGC1528) these brighter stars must also be considered part of the group.
March arrives bearing the promise of better weather. February has been a challenge in many ways. Several objects in my observing plan proved to be beyond the ken of my scope, skills, and the conditions under which I observe. However, the very fact that these objects proved elusive, helped me refine my sense of what DSO's are susceptible to my eye, scope and seeing limitations. Often we learn more from our failures than our successes...
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End of February, 2001 Observations
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