by Matt Tarlach
Sunday night, April 30, I enjoyed a fine observing session at my favorite site near Fiddletown, in the California Motherlode. Conditions were excellent, with fine transparency (limiting magnitude 6.4+) and seeing 4 out of 5. As the night progressed humidity rose and transparency decreased somewhat (down to a limiting mag of "only" perhaps 6.2), but the air remained remarkably steady until some high clouds slid in and cut the night "short" at about 3:30 AM. Instrument was a 12.5" f6 dob.
I began the night trying to catch what I could of the constellations of Autumn, now rapidly disappearing in the West. From Fiddletown that is the one point of the compass where skyglow is noticeable, rising from the myriad lights of the Central Valley. Dennis Beckley, with whom I shared the site that evening, advised me to give up on Gemini and Camelopardalis and turn my attention to the East, where the skies are dark enough to spot 5th magnitude stars all the way down to the horizon. But I was determined, and wound up pleased that I was able to catch some Winter Wonders before they slipped away into the sunset.
Dennis and I opened the session by splitting some doubles, as twilight turned to night. First up was 78 UMa, with a separation of 1.5". That sounds tight, but with the steady air and good optics in both of our 12.5-13" scopes, it was no contest. 380x in my scope (5mm Vixen LVW) revealed that the bright, yellow-white primary was trailed closely by a much fainter companion, which I saw as gray-blue. Colors appeared somewhat different in Dennis' scope; he was using a 4.8mm Nagler. Encouraged, we turned to Struve 2054 in Draco, with a cataloged separation of 0.9". Hmmmm, I thought, I can't recall ever splitting a sub-arcsecond double before...but now there it was, with noticeable black space between the two airy disks! The two stars were close in brightness, both yellow white. We looked at a few more close doubles in the same part of the sky, selected from an article that Dennis had clipped from Sky & Tel, before the night deepened to where I could start going after the faint fuzzies I'd targeted for the session. What follows are the highlights of that tour:
IC443 is a supernova remnant in Gemini. Dennis (who's working on the Herschel 400, Part Deux, and whose eyes have gathered many more photons than mine) told me to look for a miniature version of the Veil Nebula, but I found this object much more difficult. With the aid of an OIII filter I was able to detect both arcs, spanning about 3/4 of a degree. Bumping the power up from 70x (27mm Panoptic) to 162x (12mm Nagler) helped increase the contrast. Compared to the delicate, filamentary Veil, IC443 is thicker and "lumpier" in texture.
Nearby Collinder 89 was not on my list, but I swept it up in hunting for IC443. It is a large, loose open cluster, with a few dozen fairly bright blue-white stars scattered across an unresolved background glow.
NGC2371 and 2372 are two halves of the same planetary nebula in Gemini. This is a very interesting object, fairly large and bright, the two lobes not appearing connected, with an easily detected star precisely between them that is likely the "central" star. The western lobe is brighter and more concentrated, with some internal detail visible at 237x (8mm Vixen LVW). The sightly dimmer eastern lobe is less condensed, without visible detail. The OIII filter improved contrast but dimmed the nebula somewhat, suggesting that it shines at least partly by reflected light.
Abell 21, aka PK 205+14.1, is best known as the Medusa Nebula. At 70 and 162x, it appeared very large (cataloged at ~10') and very faint, not there at all without the help of an OIII filter. I could make out an overall "comma" shape that made me think of "Half-a-Helix," but no other detail. This one will be worth another look next Winter, when it is riding higher in the sky.
I've seen NGC2392, the Eskimo Nebula, many times before but had perhaps my best view yet on this night. At 380x the inner shell was well defined, both with and without the OIII filter. Combined with the diffuse edge of the outer shell, I had my first clear impression of the "furry hood" resemblance which must give this object its name.
I had other targets in Gemini, but they were slipping too low for good viewing so I moved to Sextans and NGC3115, the Spindle Galaxy. This provided a nice view: fairly large, bright, considerably condensed with a bright core area...but no competition aesthetically for the glorious dusty northern edge-ons like NGCs 4564, 4631, or 891. Viewing at 162x I had the impression of a dust lane to the eastern side.
Swinging back to the North, I sought out NGC2366 in Camelopardalis. This faint galaxy, one of Steve Gottlieb's Spring Highlights, is remarkable for the bright HII region that dominates one of its extremities. At 162x this very small nebulous patch is the only object at first evident in the field. It is squarish with irregular edges or dark lanes. Looking more closely, and increasing the power to 212x (9mm Nagler), I could make out the galaxy proper, very faint but fairly large, a pale, elongated haze, generally rectangular but with mottled edges, trailing to the Southeast from the bright patch.
J-E 1 is a planetary in Lynx that I learned about via an article by Jay McNeil published in Sky & Tel some time ago. In his sketch, done with a 16", the nebula is a curious eared donut with some filamentary structure. After perhaps 20 minutes of hunting, I glimpsed a fairly large, but extremely faint, roundish, possibly annular glow at 162x with the OIII filter. Perhaps Jay has a better eye than I, or his site is better, or there is a big difference between 12.5 and 16 inches....probably all three.
NGC4027 (aka Arp 22) in Corvus is a fairly bright, somewhat small, unusually shaped galaxy. The brightest area is off-center, with a dimmer element curving gently to one side and resembling a single spiral arm.
UGC5459 in Ursa Major is another of the Spring objects highlighted on Steve Gottlieb's web page. It is a somewhat small, fairly faint, edge-on galaxy with a bright foreground star almost touching one end. At first the galaxy looks like a diffraction spike thrown by the star!
Hickson 56 is a chain of 5 galaxies in Ursa Major. I was able to detect 3 objects, each very small and faint to extremely faint, arranged generally East-West. Comparing my sketch to that which illustrated Gottlieb's Hickson article in Sky & Tel, I can see I did not detect HCG56a, but did partly resolve the central triplet into two components.
While looking through the Uranometria charts covering Ursa Major, I "discovered" an attractive group of fairly bright galaxies, dominated by NGCs 3982 and 3998. With these two bookends, a total of five galaxies were visible, arranged in a neat crescent nearly 1/2 a degree across. Views like this are where the Nagler-type eyepieces really strut their stuff: the 12mm type 4 provided enough power (162x) to darken the sky background and bring out differences in the galaxies' morphology, while the 1/2 degree field was wide enough to encompass all of them at once.
NGCs 4490 and 4485 in Canes Venatici together comprise #269 in Halton Arp's catalog of peculiar galactic objects. 4490 is a large, bright galaxy curved into a gentle S-shape. I'd call it a very elongated, warped elliptical, with subtle mottling. 4485 is a somewhat small, somewhat bright, irregularly shaped galaxy just of 4490's western tip.
NGC4631 is a beautiful, very large, bright edge-on, sprinkled with dust and bright patches. One edge appeared more dusty than the other. Nearby NGC4627 is small, somewhat faint, slightly extended. The two galaxies add up to Arp 281.
A degree or so from Arp 281 is NGC4656/7, the "Hockey Stick Galaxy." This strange object is large and very elongated, but somewhat faint, of uneven brightness, with the brightest areas near the center and at the blade of the "stick." These brighter areas had a granular appearance, likely due to dust, but if this was a cluster rather than a galaxy millions of light years away, I'd say it was on the verge of resolution into stars.
NGC6153, a planetary nebula in Scorpius, is small, somewhat bright, with an asymmetrical shape, possibly darker in the center. It forms a pretty diamond arrangement with three fairly bright field stars.
NGC6369 the "Little Ghost," is another planetary, located neatly inside the bowl of the Pipe Nebula in Ophiucus. It is small but fairly bright, appearing annular even without the aid of an OIII filter...like a tiny version of the famous Ring of Lyra.
As a final challenge to close out a fine evening of observing, I tracked down PK64+5.1, "Campbell's Hydrogen Star" in Cygnus. This is one of the deep sky challenges listed in the RASC's Observer's Handbook. By carefully comparing the eyepiece field to the corresponding chart in Uranometria, I was able to pick it out from among the myriads of stars in this rich sector of the Milky Way. Once I pinned it down, I jacked the power up to 380x, and could see a very small halo surrounding a star (or starlike object) of about 10th magnitude. The halo was fairly bright, though difficult to make out at lower powers because of the proximity of the bright central "star;" without very good seeing this object would be very difficult. The RASC Handbook lists the size as 8", but that figure may apply to a faint invisible halo; I thought the visible ring was no more than 3-4" across.
This was one of my most productive and enjoyable sessions yet, and by no coincidence it was the first for which I developed anything like an oragnized "target list." While stuck at work during the week leading up to the session, I combed various resources looking for potentially interesting objects that I might be within reach of my 12.5", and made up a simple Wordpad document ordering them by right acension. Each object received only a one-line entry (in 14 pt type for easy reading by dim light!), with catalog number, constellation, RA & Dec, size, and a few shorthand comments on particular features to look for. This list increased the efficiency of my observing dramatically, as I was able to observe a large number of objects, many of them for the first time, without wasting time flipping through charts, or wondering what to look at next. In the future, I will try to prepare such a list whenever possible, and will add the Uranometria chart number for each object.