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Saturday, December 6, 2008

Ah, the Winter Milky Way

The Moon set at midnight last night and I was able to eke out one more half-night of observing before it takes over. Despite the temperature hovering around 19 degrees F., I observed in the Blue Ridge foothills from 11:30 p.m. to around 4:30 a.m. It was a frosty night, but clear with some passing clouds. The seeing was also better than last time out. 10-inch f/5 scope.

There are only a few comets visible for northern mid-latitude observers at the moment. I chose to go for C/2006 OF2 (Broughton), which is 10.8 mag in Lynx. Just tracing out constellations like Lynx and Camelopardalis is a challenge unto itself sometimes, but I did spot the comet. It had a stellar nucleus of about 13 mag and some glow around that to about a 60" diameter. No tail visible. The jumping off point was 5.4 mag 12 Lyncis, actually a triple system, but with the scope not yet cooled down all the way I could only pick up the 7.4 mag companion at PA 310, 8" away. The secondary is a tighter 1.7". This triple system is designated STF 948 (STF = Struve The Father).

Since planetary nebula Abell 16 (PK 153+22.1) was only about a degree and a half away from Comet Broughton, I tried for that. Jay McNeil lists the magnitude at 14, but it's apparently a very dim 14, because I couldn't make out anything at all with or without the nebula filter (DGM NPB). There is a Y-shaped star pattern that helps to locate the position, with this disk-shaped nebula nestled under one the arms. There's an observation on IAAC with an 18-inch scope, indicating I didn't have much of a chance to begin with, if any.

Here's an image from the Aladin Previewer of Abell 16. The Y-shaped asterism is on its side. North is up, West to the right. The line is probably a satellite that passed through during the exposure.

Abell 16

I had observed the large planetary Jones-Emberson 1 (PK 164+31.1) in a 30-inch before, but never in the 10. It's also in Lynx, a bit closer to Ursa Major. It was barely detectable without a filter in 52x as a large and ill-defined patch of slightly brighter sky. With the nebula filter the round shape came out and it was a bit easier. It was still visible at 96x, but faded out at around 120x. Unlike the images of this one, it appeared filled in rather than annular. The linked SDSS wide field image shows the neat asterism that looks a lot like a miniature of the constellation Corvus nearby (tilt your head to the left), which makes finding the spot easier.

Only half a degree away from J-E 1 is the tight pair of 13th mag elliptical galaxies NGC 2474 and NGC 2475. They're so close it took about 100x before I could clearly split them. 250x shows the split even better, and I could see that the northeastern of the two, NGC 2475 is the brighter, even though it's listed as the dimmer in the Historically Corrected NGC. There's a 9th mag star very close.

After a break to warm up in the car, I moved over to Auriga.

IC 2149 is a small but interesting planetary nebula about 40' west-northwest of the 4th mag orange star Pi Aurigae (35). The planetary is 11th mag, so it's plenty bright, but stellar in low powers. The central star is 11.6 mag, so it dominates the nebula. However, as I increased power with the nebula filter on, I could see the nebula appears to be elongated west-southwest to to east-northeast. This can be clearly seen in the linked image, which is much larger and more detailed than you'll ever see it in your scope. Try this one on a night of good seeing with a filter to help dim the central star.

NGC 1931 is a reflection and emission nebula near the familiar open cluster M36 in Auriga. This whole area is full of cool stuff, and I may end up doing a "Space Walk" program for some of these objects. While the nebulosity is about 4-5 times less in extent in my 10-inch than in the many images of this object, this is one of those objects that you just have to see live to appreciate. Why? because there's a tiny cluster of at least four stars in the center that is most bodacious, but gets burned out in many of the images I've seen. The linked image just managed to avoid total burnout. The image also shows that the cluster is actually quite a bit more populous. The three brighter stars I can see form a really tiny triangle, with a fainter fourth star a little further off these to the north. This "little Trapezium" is ADS 4112 (BD+34 1074). See if you can spot them all. My filter didn't help at all with the nebulosity.

From there I moved over to IC 417, which is just a scattered group of stars with a slight bit of nebulosity with the filter in my 10-inch. IC 417 is a much larger area of nebulosity, but not as bright in any given spot, so it's relatively unspectacular visually. The linked image shows NGC 1931 on the left and IC 417 on the right.

But wait, that's not all! Stay in the area and you'll find IC 410/NGC 1893, a big bunch of stars and nebulosity about a degree to the southwest of IC 417. This one does respond well to my nebula filter. I've looked for the "tadpoles" in a 30-inch to no avail.

About 2/3 of the way from IC 417 to M38, which is another great open cluster, is NGC 1907, a smaller cluster but quite dense. All three of these objects are visible in this image, with M38 on the left, NGC 1907 in the middle, and IC 417 on the right. I spent some time on both M38 and NGC 1907 in higher power- nice views of both.

With haze and clouds starting to take over, I took a look at Saturn. The planet presents an interesting view in the scope now. The rings are not quite edge-on, but still showing as white-yellow lines on each side of the planet, become inverted into a dark line (the shadow) across the equator. Looks like the star chart symbol for a double star.


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