Watching the Stars Come Out
Planets
Deep Sky
Watching the Stars Come Out
"I like to arrive at SCAC's Bonny Dune observing site as the sun sets. I like to setup Argo as the last vestiges of dusk illumine the western sky. I like to bid adieu to the few remaining veil-like clouds as they drift eastward - bathed in those final rays of a lowering solar orb. I like to watch as the first few bright stars of the season take resident in a deep blue darkening sky.
I like to turn Argo (or the Pup) on the brightest star in the skies middle third. I like to assess the quality of the seeing, whether a "heat plume" has taken temporary residence in the optic tube and whether the alignment is spot on. I like swinging the scope around on the nearest bright double star, or whatever planet that might be accessible at the time.
I like doing all these things because they create a "moodus observatum". They help me establish momentum. They are part of my own private ritual and are a big part of my observing experience.
But these operations are not essential. I can of course, arrive late and assemble the scope in darkness. I can of course, miss the descent of the blanket of night. I can of necessity, attend a star party on speculation - speculation that the thin clouds encroaching on the preserve of the stars will part and a fine night will reveal itself."
During last night's SCAC Bonny Dune star party I got what I like...
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Planets
150mm MCT Argo and I pulled up at the locked gate of the SCAC Bonny Dune observing site just after sunset. Shortly thereafter, fellow observer Richard - bearing a 9.25 inch Celestron SCT - and I watched as a couple approached the gate and greatly improved our chances of enjoying what was shaping up to be a very inviting night sky.
I had Argo up and scoping even before the very first bright stars came out to play. As Richard assembled the big SCT on its GEM, I was already getting my first views of the Red Planet well up in a Carpricornian southern sky. Thin but contrasty Sinus Sabaeus stretched just south of the planet's equator. Edge focus was dicey - but there it was - another example of high contrast maria on a sub 6 arc-second gibbous disk.
While I made a study of the incredible shrinking planet, Richard piggybacked a 300mm telephoto lens and 35mm camera onto the main tube of the SCT. Aside from capricious stargazing, his was also to be a night of capturing wide-frame images of the night sky on celluloid. Richard planned on shoots of The Great Andromeda Spiral, Seven Sisters Cluster, Great Nebula in Orion, and the Double Cluster in Perseus. (Subsequently Richard posted me the URLs to his prints and I included thumbnail shots as accents throughout this report. NOTE: All accompanying photos (c) 2002, Richard Gray of www.sizzlefish.com.)
As Richard continued his setups, Fellow SCAC club member Dan backed in bearing his much-appreciated Takahashi FS-102 apochromatic 102mm refractor. Dan and I had emailed. This would be our night we would compare views and get a sense of the relative merits of Argo and the Tak on planets and deepsky.
Two of the Gas Giants (Saturn and Jupiter) were favorably placed for the occasion. Saturn had already entered the skies middle third, while an ascending Jupiter lay well above the treetops to the eat northeast. Initially, seeing stability was decent (7/10) but degraded to 6/10 as the night proceeded.
Before too long all three scopes were up and at it. Only Argo took Mars-light however. As mentioned, that view was not particularly sharp. Image scale - even at 360x - was marginal. Saturn and Jupiter beckoned.
Saturn was our initial comparative study. The big SCT, despite slightly inferior optics to that of the smaller scopes, used its aperture to fine advantage. Though the Cassini division was less than a sharply etched ribbon running between the outer and middle ring system, all the many features we Saturnaphiles know and love were in evidence: Encke Minima, Dusky Ring A, South Equatorial Belt and Blue Gray mottling all apparent in both Argo and the SCT. At best the APO gave hints of Encke, but the Dusky ring was not in evidence.
To be clear, sky stability was not a constant 7/10. You had to spend a little time at the eyepiece of each scope to get the most solid views. Although efforts were made to match magnifications as much as possible, Argo tended to run a little higher than those used in the Tak and the SCT's. The Tak gave a distinctively finer background sky than either of the two obstructed - and larger apertured scopes. This persisted throughout the evening with Argo running a very close second - especially when Dan's 16mm Nagler was loaded into the diagonal. The nod for the most aesthetically pleasing views of the night go to the fine refractor.
Turning the three scopes on Jupiter revealed a slightly different picture. Once again, the superior resolving power of the SCT gave better views of individual bands and features. The NTB was more cleanly delineated, and two faint barges seen along the SSTB were more easily detected than through the smaller scopes. (However, a satellite transit gave similar high contrast views in all three. But due to less than perfect stability, none of the scopes revealed the Galilean itself.) Although the APO had fallen down a bit on Saturn, it came roaring back on Jupiter. Despite the SCT's superior resolution, there is something about the luminosity of Jupiter that gave the "aesthetic edge" to the Tak. Dan and I agreed that a finely crafted, unobstructed four inch scope gives just the right balance between resolution and brightness.
Frankly Argo's views were not the APO's equal and it soon become apparent why: Argo's diagonal, barlow and eyepiece collection do not lend themselves well to low contrast details. Essentially the image through the Ultra was a bit too "soft" and challenged the eye's ability to accomodate. To test this I tried Dan's super-multi-elemented 7mm Nagler through Argo (and kept it very close throughout the evening). At 260x, the Nagler gave a more contrasty, and darker framed view of the planet than Argo's 10mm 180x Ultrascopic. This despite the handicap of contrast-robbing higher magnification. To confirm this, Dan tried the 10mm in the Tak, and agreed with the diagnosis.
Later that evening, fellow SCAC member Mark arrived on the scene with his Televue 85. Based on my experiences with the 80mm Pup achromat, I had a working theory that - somewhere between Dan's 102mm and an 80mm version of the same - Gas Giant views would no longer be well met. In fact, we had already seen something of this in the case of Saturn. The four inch didn't have the necessary image illumination and resolution to give the kind of views 150mm Argo gave. As it turned out - and keeping in mind some seeing degradation - this pretty much proved to be the case with Jupiter as well. Despite aesthetically pleasing views of both Gas Giants - one's visibly superior to those seen through the Pup - 85mm's didn't quite make the grade. Both Saturn's Cassini and Jupiter's NTB needed a bit too much attention to detect. But once again, seeing had degraded (although Argo's view of Saturn at the time was still pretty sassy.)
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Deep Sky
Before Mark arrived, fellow SCAC club member Chris turned up with his 16 inch Meade Starfinder. While Chris setup, Dan, Richard and I made an attempt on edge-on NGC891 in Andromeda. Before doing so, resolution of Almaak's close .5 arc-second companion was tried. Marshalling all the magnification possible (540x through Argo, 360x through the Tak, and maybe 600x through the SCT), only Argo's view hinted at the close companion - this as a slightly distended primary airy disk. Something about the SCT made clean disk resolution difficult, while the round, but largish disk seen through the APO "swallowed up" the close secondary. Of course, Almaak's more distant blue-green secondary was easily seen in all scopes and the blue-green airy disk was especially attractive in Argo at high power - despite some flaring caused by less than ideal seeing stability.
Early on, seeing transparency was not quite as fine as later that evening. Sweeping east from Almaak, I was unable to locate the coy edge-on. Richard found it immediately in the SCT. On slight aversion, the galaxy's frontier was well delinated. Eye movement showed the dark lane slicing across the spiral's edge. It wasn't until later in the evening - as the sky overhead revealed 5.5 magnitude stars - that I located this "thin lenticular slice of luminosity" in Argo. Through the 150mm, and on extreme aversion at 50x, I was able to plainly see the galaxy's frontier and full-extent - but no bisection was possible. About the time Argo turned up the galaxy, Chris caught it in the 16 inch - but at 70x the view was inferior to that of the SCT. It was only after increasing the magnification to about 120x, the full extent of the galaxy revealed itself along with the lane - but some aversion was still required.
In fact, the large scope's image brightness was afflicted throughout the night -especially at lower magnifications. No matter where it was turned, the "gauziness" of high thin clouds, and radiance of various light domes conspired to create an unpleasant "greyishness" in the field of view. Meanwhile, Argo, Dan's Tak and Mark's TV-85 all continued to give high contrast views of galaxies, clusters, and nebulae.
There were exceptions to this. I loaned Chris the Orion Ultrablock filter for views of The Great and Flame Nebulae, plus NGC281 in Cassiopeia and M1 in Taurus. The effects on the Flame and M1 were marginal, while that on NGC281 was significant and the Great Nebulae in Orion was stupefying! Vast clouds of undulating nebulosity just kept rolling away from M42 as we swept the field - extarordinary!
Dan and I turned our scopes on the Great Nebulae too - but without the filter. Comparing views, we could only conclude that the Great Nebula won. However, Argo had a bit of an edge revealing the E and F members of the Trapezium, but both scopes could do so during moments of especial steadyness when the three brighter members showed their tiny little airy disks...
We also turned the scopes on M1 and M76. This later perplexed me because I remembered a particularly fine view of "The Little Dumbbell" through Dan's Tak during a previous star party. In this case both scopes gave comparable views with the advantage going to Richard's SCT... In no case however did the frontier of the double planetary stand out in bas relief. All threes scopes showed central condensation, general orientation, and a soft frontier on aversion.
Argo, again sans filtration, gave a better view of variations in surface brightness on M1 than the Tak. Again, the Tak's background sky was slightly superior however. Richard's SCT showed a wee bit more than Argo - but the two were more closely matched...
It might appear that scope comparison was the focal point of the night - in fact that was a large part - but not in the main. Most of the time we just kept thinking up studies to look up either collectively or individually. Then of course, we shared views - that's what a star party is about.
Among the more interesting events was the fact that Mark was able to star hop his way to NGC891 using the TV-85. Incredible! Here's this 13.5 magnitude average surface brightness galaxy being turned up at 40x through some three and change inches of aperture - and as you might expect, there were plenty of witnesses!
I also managed to pull off a bit of a longstanding challenge myself. For, under 5.0+ southwestern skies (well outside the Santa Cruz lightdome), I tracked down that 13.9 average surface brightness galaxy NGC1300 in Eridanus. However, at best, only Mark and Richard got a hint of its presence in the field of view...
Later in the evening, I visited with the "Grand Galactic Duo" - M81 and 82. Probably the finest view of this pair I've ever had - simply gorgeous. Mottling in M82, and extended spiral extensions in M81, both present.
But this was not the best of it, for you see, once the Hunter left the Santa Cruz lightdome, I turned Argo on M42 at 50x. Transcendental! Here was the most spectacularly, photogenic view of the Great Nebula I can ever recall seeing. In fact, no CCD image or print could even compare.
So I just hung out...
And gazed in absolute awe, wonder, and rapturous appreciation.
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Before Mark arrived, fellow SCAC club member Chris turned up with his 16 inch Meade Starfinder. While Chris setup, Dan, Richard and I made an attempt on edge-on NGC891 in Andromeda. Before doing so, resolution of Almaak's close .5 arc-second companion was tried. Marshalling all the magnification possible (540x through Argo, 360x through the Tak, and maybe 600x through the SCT), only Argo's view hinted at the close companion - this as a slightly distended primary airy disk. Something about the SCT made clean disk resolution difficult, while the round, but largish disk seen through the APO "swallowed up" the close secondary. Of course, Almaak's more distant blue-green secondary was easily seen in all scopes and the blue-green airy disk was especially attractive in Argo at high power - despite some flaring caused by less than ideal seeing stability.
