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Friday, January 23, 2009

Gemini, Monoceros, and a Frosty Leo

Unusually cold weather brought a lot of unusually clear nights recently. But it wasn't until last night that it was finally "warm" enough to meet my own standards (above 20 deg. F) for observing, so it was off to the Blue Ridge foothills. Some passing clouds covered a good part of the sky at times, but curiously my observing was affected very little. I guess I picked the right spots this time. 10-inch f/5 dob. I observed from 9 p.m. to 2 a.m. Transparency variable- 8/10 at best, seeing 8/10 to almost 10/10 at times. Limiting magnitude variable across the sky, about 5.8 at best.

I checked on comet 144P/Kushida again, which is close to the Hyades in Taurus. I had observed this last New Moon. It was bigger and a bit brighter, but otherwise not changed much. The inner core had been stellar last time as I recall, but it was larger and more diffuse this time around. The outer coma extended a good 4 arcminutes in diameter. Eighth magnitude? No tail.

I figured I'd try for 29P/Schwassmann-Wachmann 1, as it was reported to have had some recent outburts. It's in eastern Gemini near the Cancer border. I found it 9 arcminutes off the position plotted by my charting program, but pretty easy to spot as a 13th mag fuzzball about 2 arcminutes in diameter, condensing very slightly at the center. It was faintly visible in 52x but best around 140x. Gave the impression of a cloud of debris. Now if I could only learn to pronounce the name without sounding like I'm spitting out toothpaste - one of the more unfortunate co-discovery pair-ups!

I'm an opportunistic observer, so I turned my attention to a pair of faint galaxies residing far beyond the comet, but in nearly the same line of sight. These are NGC 2480 and NGC 2481, magnitudes 14.3 and 12.7 respectively. 2481 is much more condensed and therefore easier, with a distinct NNE-SSW orientation. 2480 is a whole lot dimmer, and I could just detect its presence very close to the NNW in 312x using close averted vision (looking only about 10% of the field of view away versus the normal 20-80% for me).

Being in a leisurely observing mode, I meandered over toward the Eskimo Nebula, on the way picking up the open cluster NGC 2420. This is an 8.3 mag group of perhaps 30 stars visible in my 10-inch. The diffuse glow of dimmer background stars suggested this contains more stars than I could resolve. The cluster is in something of a twisted diamond shape with a tail of three stars that curl to the south and then west. The closest in of these three stars showed up as a nice double in 250x, with a position angle of about 220. The Hubble Guide Star Catalog identifies the primary as GSC 1373:2235. This is a nice cluster.

If you go from the cluster in PA 070 about 40 arcminutes you'll find Struve 1124, which consists of two 9th magnitude white "eyes" staring back at you with a straight line of three stars right next to it, a curious little asterism. Here's an image from the Aladin Previewer:

Struve 1124

The Eskimo Nebula (NGC 2392) was just great with such good seeing. The central star was nice and sharp and the bright inner circle well differentiated, along with hints of detail in the "parka." The DGM narrow passband filter dims the central star down almost to invisibility, providing a better view of the shells, but I prefer the unfiltered view because the central star is a key element in the attractiveness of this planetary nebula.

Again, being opportunistic (a euphemism for lazy, as you may have guessed by now), I took a short 20 arcminute walk over to 14.5 mag galaxy UGC 3873 from there. This galaxy showed up as a very dim slash, very soft with no central condensation. It took 140x plus just to see it at all. This is another one for which I had to use "close" averted vision, it was so dim. This is definitely one that my eyes wouldn't have picked up just scanning around the area. The linked image is pretty cool, showing the Eskimo Nebula and the dim galaxy off on the side of the frame. Yeah, it doesn't take much to get this old boy excited.

In my Nov. 27, 2008 post, I described looking for and not finding Sharpless 2-188 and compared it to the Medusa Nebula. With that relatively fresh in my mind, I figured to take a gander at the Medusa, Abell 21. This planetary nebula is in southern Gemini, just over the border from Canis Minor. Without a filter I could only get a sense that there was a slight brightening in the proper position. It was much better with the NPB filter on. After studying it for a while, I could begin to make out the crescent shape, the horns and opening pointing toward the NW. 60x was best. Any more and it just faded out. The best strategy on this is to have a nebula filter, dark sky, low power, and good image showing some of the surrounding stars to help you get the right location and orientation, since it is pretty large at about 10 arcminutes across.

Moving 36 arcminutes to the NW as the opportunistic crow flies is a decent open cluster, NGC 2395. Normally I like my clusters dense, not scattered, but this one makes a neat flying bat or pterodactyl shape, so I put it on my list of "worth checking out." Okay, you don't see it? Look for the head to the SW (to the lower right in the linked image), wings to the NW and SE. Hard to see it in an image - you gotta go live. About 35 stars or so. This one also goes by Collinder 144.

Two and a half degrees to the west, as the lazy pterodactyl flies, is open cluster NGC 2355. Now this one fits my dense criterion fine, with about 40 stars visible in a small patch in my 10-inch. There's a tail of stars that trails off to the south. Look 6.5 arcminutes in PA 030 and you'll see a funky little asterism of four stars in a rectangle and a brighter one at one end that reminds me of a turtle with a brightly glowing head (yes, it was getting late and I was a bit loopy by this time). Here's the Turtle from the Aladin Previewer:

Turtle (SAO 96722 and friends)

Swedish astronomer Per Collinder must have spent some time in this area because NGC 2355 is also designated Collinder 133.

At this point I decided to give the rest of the sky a little scope time and moved over to try to spot planetary nebula Kohoutek 2-2 (PK 204+4.1) over in Monoceros, the Unicorn (which also looks like a pterodactyl to me). I had no image to go by at the time, but it's supposed to be 12.5 mag and 415 arcseconds in diameter. However, it must have very low surface brightness- not surprising given its size- and I wasn't able to see it. Here's an SDSS image (13 arcminutes wide) that I haven't yet added to the SDSS pages:

Kohoutek 2-2 (PK 204+4.1)

But as luck would have it, there was an interesting necklace of stars about 45 arcminutes to the SE that contains a Struve double at its eastern end, STF 986. This has a 9th mag primary and a 9.5 secondary at PA 165. I guestimated the separation at about 15 arcseconds, which is well off the cataloged 5.4 arcseconds. This pair is the same as WDS 5572 (Washington Double Star catalog), which lists 54 arcseconds. That seems a bit wide to me. 15" and I'm stickin' to it.

After a break I wandered over to one of my favorite objects, Hubble's Variable Nebula (NGC 2261). The brighter part of this roughly triangular nebula formed a hooked bill shape, or a blunt claw, due to a dark incursion just back of the star R Monocerotis, which gives the nebula its glow. A fairly dramatic fade-off to the NE gives it more of a crescent shape (you thought I was going to say pterodactyl shape, didn't you?). In lower powers the dimmer parts fill in more and it looks more triangular or fan shaped.

I had added the Frosty Leo planetary nebula to my Jay McNeil list of planetaries compiled for The Sky v. 5, but had never observed it. So I headed over to the Big Cat to check it out. This one is relatively bright at 10.5 mag, but it's small, as in starlike, at lower powers, and so a good position and chart is essential. The higher the power, the better to make out its slightly elongated shape. There's a star close to it that helps. The NPB filter dims the nebula about as much as it dims the star, so no real assistance there. Steven Waldee has a nice discourse on this object after he loaded the position into his newer Sky version 6 after much gnashing of teeth and observed it.

Steven remarked that galaxy NGC 2958 was close to Frosty Leo but he neglected to try for it. So I did. He didn't miss much. Just a small spot, nothing more, in 156x.

But not too far away to the NE is an interesting trio of galaxies, NGC 3016, NGC 3020, and NGC 3024. The brightest is 3020 at 12.1 mag, followed by 3016 at 13.2 and 3024 at 13.3. All three fit within a 15 arcminute field of view. The nuclei are all condensed pretty well, but I needed 80x or more to see them well. 3020 and 3024 are more elongated and their orientation is discernible. 3016 is harder to get a handle on. If you're up for a challenge, there's also 15.2 mag NGC 3019 in the middle of the trio, but I can rarely get that deep with the 10. This SDSS image (13.5 arcminutes wide with north up) shows all four galaxies (3020 top, 3024 left, 3019 center, and 3016 lower right):

NGC 3020 group

A quick look at Saturn with three moons off to the west and Titan on the east, and it was time to put away the toys and head home. I left too early to take a look at Comet Lulin. I'll leave that for another night.