Be Careful What You Expect...
Hello, Where Did This Sky Come From?

Be Careful What You Expect...

By late afternoon Thursday, continuing poor weather these parts showed hints of a possible sky. But I'd seen such "hints" before and did not hold them in high esteem...

By sunset the sky was completely devoid of clouds. The air felt reasonably dry and there was even a sense of depth to it. - But again, I'd been lured out into the evening air by such appearences before...

This is the time of year when the sky "flirts" with those of us who observe out of the Santa Cruz Mountains. It is a time when the arrival of true skydark is often accompanied by low flying clouds - creeping down from the ridges above. Historically such evenings give maybe an hour of "not so quality time", before the scope is left standing out on the back lawn. Meanwhile, I come inside to write up my all-too-brief observing notes and feed the illusion that "things will improve"...

But I was having ALL of it. Why? Because this last month has been one long, continuous stretch of rain, leading to overcast, leading to partial clearing, followed by sucker holes. And through those same sucker holes the occasional glimpse, of a gauzy, 4th magnitude sky dominated by a waxing moon.

Well the Moon has moved on. And despite lingering, limited transparency, I'll take whatever I can get...

Had the 80mm Pup out early. Took a look at a 140x Mars as soon as it could be tracked down by eye. The planet now culminates to the south at sundown. Incredibly small disk (maybe twice Uranus-sized). Caught two polar brightenings and a strange latitudinally-oriented darkening north of the equator. Strange, because unlike most "contrast-effect" illusions (brought on by small image scale) this one lay horizontally - not vertically.

In researching this (as I write), learned that a very horizontal "Sinus Sabaeus" lay right where my "contrast effect candidate" was seen. Coincidence? Or is it really possible to make out maria with the Red Planet some 7.1 arcsecs in diameter through an 80mm scope? Have to say that I needed a red filter to bring it out. Also have to say that the edge-focus wasn't half bad. Hmmm...

Ported the Pup in the north viewing station. (No big deal - even while mounted on the Skyview Deluxe). At the time Vega the only star bright enough to be held unaided. Ran a quick star test on the little scope. As noted elsewhere, the Pup is definitely "undercorrected". Magenta finge around a well defined green outer diffraction ring, followed by a gap and a well-defined but thinner inner diffraction ring with the scope maybe 3 wavelengths intrafocal. At center, and for the first time, noticed a "void" instead of a starpoint. Meanwhile, the alignment looked very good intrafocally.

Extrafocally, the bright starpoint lay visibly offset south. The bright outside ring was green-fringed magenta, encompassing a large vague disk of magenta bleeding toward the offset starpoint. Gossamer inner diffraction ring could just be made about halfway toward the center. Although the blue and green filters do improve contrast outside focus, neither were used during the check. Seems pretty clear to me, the Pup, at best, is about 1/4 wave undercorrected...

Centered the Pup on the Double Double. Nice clean, 140x split. Could even tell that the western member of the Epsilon-2 pair displayed a larger virtual airy disk (VAD) than its confrere. Despite the fact that Vega showed in focus diffraction rings, none were seen around Double Double members. Keep in mind that by this time I couldn't even hold 3.3 magnitude Gamma Lyrae direct. A check of the Ring Nebula (continuing with 140x) wouldn't even reveal the location of the "Challice of the Ring" asterism - and the Ring itself could not be seen as a true annularity.

So I hung around the Ring "watching the faint ones come out". Meanwhile, the Lyre continued to slip west - well outside the skies middle third... Just before making out a semblence of the Challice, the Ring started showing hints of a "dark" core. Looking up, noticed I could just hold 3.8 magnitude Beta Lyrae.

Shifted on over to Delta Cygni. Two semi-persistent brightenings could be seen northeast and southeast. The northeast brightening is the more offensive of the two. I suspect that the coma induced by the Pups misaligned positive element (the starpoint offset seen during the startest) is probably at work here...

The early plan was to do some limiting magnitude checks using AstroTalk reference charts. (The charts show stars in open cluster's M29 and NGC6910). M29 was a wee bit long in the finding. The cluster was "hand-entered" into my star charts as a result of the lack of critical detail in the originals. Hand entries always undermine my confidence when looking for such a study. On most nights, Argo's 35mm finderscope is enough to track down this faint cluster. But I was using the Pup (with its 24mm finder) at a time when the sky was still fairly bright (perhaps 4.0 ULM at this time). So I pulled off one of the barlows and dropped down to 75x. Then began sweeping the sky south and west of Gamma Cygni.

Once I managed to get the cluster in the field of view, it was a cinch to recognize it. Cluster looks variously like a "shopping cart", a mini-version of Cassiopeia or a basket - whatever you prefer. At 75x I found that I was just able to hold a 10.2 magnitude star from the chart direct - while a 10.6 magnitude star also seen on the chart actually appeared brighter to my eye - strange. There was little improvement in going to 140x - except that I could just catch a 12.5 magnitude star on eye movement and a 12.0 on extreme aversion.

Checking the sky, signs of incipient "observing washout" were apparent. Not so high, thin clouds moved "on little cat feet" across the sky. At best 4.0 magnitude Nu Cygni could just be held southeast of Deneb.

There would be no chance on this evening to track down 7.5 magnitude open cluster NGC6910 - despite the fact that it is to be found in the same field of view as 2.3 magnitude Sadr.

The clouds just kept piling up...

Hello, Where Did This Sky Come From?

Friday, December 7, 2001 - Oh yes, were was I?

Had more on tap for astro-exploration on Thursday than sky permitted. Not wanting to leave things undone, went out again this evening. This, despite expectations of the same meteorological behaviour as last. True to form, low clouds did begin creeping in - but not until 8:00pm - well after I had accomplished most of the evenings planned undertakings. I guess I'll have to take my holiday-season obswerving in small doses...

Seeing stability was initially much poorer this evening than last. At best 6/10. No airy disks visible. Had to pretty much stay under 75x with the Pup - although I did bump things up for some telescopic limiting magnitude checks.

Speaking of which - managed to turn up 7.5 magnitude 7 arc-minute sized NGC6910. Given an average surface brightbess of 11.4 under 4.9 ULM conditions - not an easy task. Found it about a degree northeast of Sadr at the Crux of the Northern Cross. Could hardly recognize the group as a cluster. Particularly given the field. Small (3X5 arc minute) patch of half-dozen averted-visibility stars nestled in an elongated triangle of 7th and 8th magnitude field stars. The group "swelled" to a dozen stars on eye movement at 140x. None could be held direct - especially given the fact that at 75x the Pup could just hold stars down to magnitude 10.8 (11.2 at 140x).

Of course, had to revisit M29. Probably saw a little deeper than last night at this same (75x) magnification. However, lack of magnitudinal resolution in the cluster's chart did not make it possible to determine how much deeper. Can say, however, that I was able to pick out one of the "basket" stars on aversion. Don't recall doing this last night. Kind of suggests that such stars are in the 12 plus magnitude range.

Iota Cassiopeia once again lies in a respectable part of the sky. At 140x was not able to resolve the tighter AB pair (something that can be done under 8/10 seeing through the Pup.) Was able to make out the 12 plus magnitude field star regularly checked last observing season. BUT the star could only be held on eye movement. Sky transparency near Iota not quite as good as it was in Cygnus. But 4.2 magnitude Kappa could be held direct unaided. So as originally conceived, the star is probably somewhere in the 12.5 magnitude range.

All this leads up to the Great Cassiopeia Open Cluster Tour. Last year I visited with all these studies and made detailed notes through Argo. All the clusters at that time (on slightly darker nights no doubt) gave really fine clusterlike views (especially my favorite NGC7789). Was particularly fascinated with the prospect of revisiting them all through the 80mm Pup. So, not wanting to curb my patience, started with my favorite:

Open Cluster NGC7789, Magnitude: 6.7, Apparent Size: 16', Average Surface Brightness (ASB): 12.4, Recommended Aperture: 150mm (refractor) I'd like to think that the 80mm Pup would give a decent view of this one - but unfortunately not under ~4.5 ULM seeing. In fact, could see two to three dozen stars at 50x - nearly all required some aversion. Two of that number direct. This suggests that - on a decently transparent night (5.5 ULM) - the Pup would probably show a swarm of very faint stars and give a passable view of this lusciously swirling group...

Open Cluster NGC457, Magnitude: 6.4, Size: 13', ASB: 11.6, Recommended Aperture: 125mm: Easily recognized as the famed "ET Cluster". Two dozen stars visible - all direct at 50x. Certainly well within the Pups range this evening - despite the seeing. Have to try this one on a darker night with the Pup stopped down a bit as a test. The view was just too nice to believe that it takes any more than 75mms to get an "optimal" view.

Open Cluster M103, Magnitude: 7.4, Size: 6', ASB: 11.0, Recommended Aperture: 125mm: This one looked more like an asterism than a cluster at 50x. Reminded me of "Delphinus". Compact group of bright stars with maybe another half-dozen faint members seen on extreme aversion. Could be a real test for the Pup - even through a "deep" sky - to see it as something other than an asterism.

Open Cluster NGC663, Magnitude: 7.1, Size: 16', ASB: 12.8, Recommended Aperture: 200mm: Larger group in both apparent size and number than M103. Maybe 2 dozen stars possible. Unlike M103, no really bright ones. About half a dozen on-the-edge stars form a crescent with the "bowl" oriented toward the southwest. This could be an decent view for the 80mm on a darker night. But it is dimmer overall than NGC7789 and of similar apparent size.

Open Cluster M52, Magnitude: 6.9, Size: 13', ASB: 12.1, Recommended Aperture: 150mm: It's easy to see how Messier would have thought this cluster "cometlike" in a small scope. Vague "arrowhead shape" group of stars embroiled in a faint mist. Bright 8th magnitude star at its tip. Overall 2-3 dozen stars possible under eye movement - very much like NGC663 but compressed into a smaller region. The higher star density accounts for its "misty" presentation. Another group more like an asterism than a cluster. But should look much better on a really good night.

Having completed the Cassiopeia Cluster Tour, swung the Pup around to determine if under marginal conditions, I could locate M33 - The Triangulum Whirlpool Galaxy. As it turned out, had very little trouble locating this large patch of dim luminosity. The galaxy showed obvious central condensation - and dare I say it, spiral arms - but only on eye movement. These particular "arms" were oriented east-west with the leading spiral curling north. Low power (50x) a must!

About this time high thin clouds really started moving in. Shifted the Pup north towards a barely visible 4.2 magnitude Theta Persi. Swept around for a bit - caught a vague patch where the M76 "Little Dumbbell" planetary should be - nothing definitive.

So with Saturn on the rise and the hour fast approaching 8:30, came in to write up my notes. Later around 11:00, caught a really fine view of Saturn through an otherwise dew-soaked Pup. Cassini displayed a decently sharpened-pencil line around most of the system at 140x. Ran the magnification up to 210. Chromatic aberration got a bit obscene, but still Cassini was albeit "unsharpened-pencil-line" present. South Equatorial Belt delineated to the Equatorial Zone - but not temperately. Three satellites possible - but only Titan direct at 50x. The 50x view of the planet was pretty much chroma-free and quite sharp.

This same was also true of Jupiter. At 50x, very contrasty - but due to small image scale, not particularly fascinating. At 140x, caught the North Temperate Belt. Also nicely delineated frontiers to the two polar regions (NNTB & SSTB). Some variations in surface texture along the North Equatorial. To my suprise, could just resolve the rift in the South Equatorial Belt - something I've always thought was "Argo's Special Preserve". There was also a sense of the Great (not-so) Red Spot - but well away from the central meridian of the planet. Confirmation on this requires research - since it looked more like a "disturbance in the (corriolus) force" than a defined spot.

NOTE: The GRS did not rotate in until several hours later that night.

Swung the Pup around on the Great Hunter - at midnight, well placed to the south-southwest. Due to limited transparency, didn't get the most rapturous view of the Great Nebula. No sign of the Flame near Alnitek either. Amazingly, despite seeing Alnitek's fine airy disk, was unable to cleanly resolve its 2.4 arc-second distant 4th magnitude companion as anything other than a "teardrop" - even at 210x. Did see the more distant 9.5 magnitude Alnitak come however - on slight aversion. Far too much water vapor in the air along with a high cloud cover for anything more definite.

Needless to say the Trapezium remained just that. Even so could barely hold the dimmest 8th magnitude member direct. So mag 10 would have been the limit this evening through such a sky against the background of the Nebula (using eye movement to locate an "E" member)...

With the Pup dripping (was it the the excertions of the evening? or the dew?), restored the lens caps and tucked it away in the study. At the risk of jinxing it, there does appear to be a general improvement in Boulder Creek Skies. Should be out tracking down them deepsky denizens again soon! MIght even get motivated to write things up on Astro.Geekjoy - but certainly on AstroTalk.

Carpe Noctem,

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