| Reports | TAC | Join mailing list |
by Jay Reynolds Freeman
When dark skies coincide with a long weekend, I don't sleep much. I took my Celestron 14 to Fremont Peak State Park, near the central California coast, on all three evenings of the 1999 Labor Day holiday. Smoke from the state's widespread forest fires impeded viewing on Friday, but declined during the next two evenings. Moderate fog on the coastal plain below contributed to dark sky, while a temperature inversion kept the Peak warm and dew-free.
On Friday, only one other observer shared the southwest parking lot with me: Not everyone will fight traffic and fatigue at the end of the week. He had an Orion 6-inch "SkyView" equatorially-mounted Newtonian. It wasn't perfect, but seemed reasonably made, with reasonable optics, though his were a bit out of collimation. Its owner, a machinist, was proudly testing large handmade setting circles, that would probably have cost more than the rest of the telescope, at commercial prices.
Because of the smoke, I restricted my efforts mostly to bright objects. There is a section of Milky Way from the west end of the "W" of Cassiopeia, through that constellation and on into Perseus, that contains a lot of non-NGC open clusters that I had never looked at. I spent much of the evening going through them at 98x. Many are large and bright; their absence from the NGC probably has more to do with selection effects based on the kinds of observing its compilers were doing, rather than with difficulty seeing them; the C-14 was mostly loafing. I looked at some "showpiece" objects, too. Seeing was okay for the big SCT, but nothing to write home about. I spent a while staring at gamma Andromedae, hoping things would settle enough for me to get a decent try at separating gamma-two, but it did not happen.
When the deep-sky part of the night was terminated by Moon rise, the waning crescent stayed a lot redder, a lot higher in the sky, than it does usually. Indeed, we had forest-fire smoke in the air.
On Saturday, a lot more people showed up; there were several large refractors as well as some big Newtonians. I spent a little while participating in eyepiece comparisons. A fellow observer had a large f/4.8 Dobson with a two-inch Tele Vue Paracorr -- a coma corrector. We tried my old standby deep-sky eyepiece for fast telescopes, a Meade 20 mm Research-Grade Erfle, in that configuration. I knew the Erfle's images would not be satisfactory at the edge of the field at that fast a focal ratio, and I suspected that the main problem was aberrations in the eyepiece itself, not in the primary mirror, but I was curious to see the effect of eliminating the coma of the paraboloid.
With the coma corrector in place, the Erfle exhibited nearly pure astigmatism at the edge of the field -- we could rack the focuser in and out and watch the star image go from a line oriented radially, to a blur, and then to a line oriented tangentially. Pure astigmatism in large amounts is rare; it is usually mixed with something else. Yet this example was almost textbook. The comparison illustrated how well corrected such more modern designs as Naglers, Panoptics, and such, really are -- with fast Newtonians, they work just fine, and are invaluable to observers trying to track things at high magnification with sluggish telescopes.
My Erfles, though, all work well at f/10 or f/11. We tried a 20 mm Nagler Type II in my C-14, and though it gave a wider field, it is not clear that its images were any better than those given by the Erfles; certainly they were not much better. It's been a long time since I have done much observing at f/5, and my personal observing style doesn't benefit from increasing the apparent field from the 65 degrees field of the Erfles to the more than 80 degrees of the Naglers -- so I have bought no Naglers. But they are great for big, fast Dobsons.
My main observing program for the night was planetary nebulae from Jay McNeil's master list. These things are tough, particularly because I went through lots of the easier ones in his collection, for the late summer sky, last year. I would spend several minutes carefully identifying the field at a moderate magnification -- 244x was as much as I cared to use -- then many more minutes scrutinizing things within it for signs of fuzziness, then perhaps still more time repeating the scrutiny while using a narrow-band light pollution filter to block background light and enhance the relative brightness of the planetaries, many of which emitted preferentially in the bandpass of my Orion UltraBlock filter. I logged another eight planetaries, but there were three more that I could find no trace of. Even the ones I saw yielded no more data than notes as to whether the planetary appeared diffuse or starlike, or had a central star visible.
I took another look at gamma Andromedae. I could see structure in the nervous amoeba of gamma-two's diffraction pattern, that did not appear to be matched in gamma-one, but I could not call it a split.
One observer wanted a look at Einstein's cross. It was not well placed then, but later, with the western side of the Great Square higher in the sky, I found the field and dropped in my Vixen 8-24 mm zoom eyepiece to see if I could find an optimum magnification for looking at it. It wanted all the magnification the Vixen had, and still wouldn't show the Cross. At 489x, I could see occasional hints of structure in the nucleus of the lensing galaxy, CGCG 378-15, but nothing I could positively identify as something other than a garden-variety galactic nucleus. The seeing was better than at Lassen Peak last month, where we had a much better view of the object. I attribute the difference to reduced transparency from the smoke. The would-be observer -- Mark Wagner's young daughter Mimi, known sometimes as the "Messier Monster" -- had gone to sleep; I hope her father remembered to tell her that she had not missed the Cross after all.
Jupiter and Saturn were visible fairly early. Seeing did not settle enirely for the C-14, but even so, I was pleased to be able to detect the wide, broad minimum in the intensity of Saturn's A-ring. This diminution of brightness, approximately at the center of the ring, used to be called the Encke Division. I don't usually see it with the C-14. Jupiter also showed a lot of detail, including assorted views of an occultation of Ganymede by the planet. Later in the evening, with the planets higher, I got a view of both in a 10-inch f/6 Newtonian with a Nova primary, at about 150x, and in an Astro-Physics 180 mm f/9 EDT, at perhaps 250x. Even though seeing had settled considerably, I thought the C-14 was doing better than the 10-inch. (And I had put the C-14 to bed already, so could not side-by-side compare.) It looked to me as if the AP 180 was showing about the same amount of detail as the C-14, thought I certainly didn't see it as often in the C-14 as in the big refractor. It wasn't a particularly useful comparison, since the C-14 did not have as good seeing as the AP, and since the AP could have been pushed to higher magnification. Still, it is nice to know that aperture helps; my SCT does not have nearly as good optics as Roland Christen's triplets, and was not really meant as a planetary telescope, yet it was doing an entirely reasonable job in quite big-league company.
On the way down from the Peak, past three in the morning, I saw out of the corner of my eye what was probably a mountain lion vaulting up from the shoulder of the road into the brush. I am not certain, but the details do a good enough job eliminating other animals that I think that's the best guess. The sighting was thought-provoking, but it was a mile or two from where we observe, and the big cats certainly are found in the area, so I went back the next night anyway.
Sunday evening was darker, with less smoke. There were fewer observers than Saturday. Occasional grumbles from the darkness and rattling trash cans showed the local raccoons were out in force, and prompted lots of loud, nervous jokes about mountain lion repellent. I started at 98x, working through a few objects reported as clusters in Herschel's original General Catalog, which are not so recognized now. The game here is to try to figure out just what asterism or star cloud Herschel saw. The C-14 is roughly as capable as the larger reflectors that Herschel used, which had speculum metal mirrors.
I've been through a score or so of these objects, and I find that usually there is something there. In a few cases, to my eye the "cluster" looks like a chance concentration in a star cloud, but more often there is an identifiable asterism, and in some cases something that actually looks like a cluster. The true bottom line as to what is or is not a cluster, is whether the stars are gravitationally bound and physically associated (it is possible in theory to have pathological cases in which there is one but not the other, but usually these two properties go hand in hand). I can't determine that any better than Herschel could, and there are some rather convincing "clusters" that are known to be just unrelated groupings on the line of sight -- Collinder 399, also known as Brocchi's Cluster or the Coat-Hanger Cluster, is one such. The most convincing "cluster" I looked at this night was NGC 7708, in Cepheus.
Some other "clusters" may have represented caution on the part of Herschel about what to leave out. I noticed a few that have linear patterns of stars. In Herschel's time, the details and circumstances of star formation were not known. Perhaps he thought that linear patterns might be actual artifacts of some unknown process of star formation -- maybe somehow stars got formed in chains -- and wanted to be sure to record any sites of this process that he had found. NGC 6839 is a good example of a "cluster" that appeared to me to be a loose chain of stars.
I got tired of that in a while, so decided to pick a constellation and go fishing for faint galaxies. I chose Aries, sort of at random, opened Millennium Star Atlas, and started star-hopping across its pages. Twenty-six galaxies later, I had had enough, and wandered over into Taurus. I resolved the Pleiades -- surprise :-) -- and saw the Merope Nebula and lots more nebulosity therein. I found a few patches of the California Nebula, and a few patches of the large nebulous complex north of the Pleiades, that contains IC 353 and IC 1995. I found dark nebula Barnard 208.
I increased magnification to 782x and looked at Jupiter and Saturn. That was way too much for seeing, so I backed off to 489x -- an 8 mm Brandon -- which was only somewhat ridiculous. I did see the broad A-ring minimum again.
Finally, I tried gamma Andromedae a third time, also at 489x, and after much patience found a few short periods when seeing settled enough that the image of gamma-two was composed of sufficiently few slow-moving speckles that I could see them separately. Each was indeed a tiny double, with visible dark space between the components. I was pleased -- gamma-two And has been closing since I last split it with this instrument, in the early 1980s. The current separation is about 0.45 arc seconds; Dawes's limit for the C-14 is 0.33 arc seconds, and the components are of unequal brightness.
I logged over 180 celestial objects that weekend, plus one possible incompletely resolved mountain lion. It was a good holiday.