Monday, October 3, 2011

The return of fall weather

The much anticipated return of cooler weather and clearer skies too has finally materialized here in Coastal Alabama, and last night was the clearest night to come along in months. I drove out to the airstrip with the 15-inch and two new eyepieces I recently acquired. There was however the annoying light from a crescent moon two days away from first quarter, but the Milky Way was plainly visible overhead as darkness fell over the airstrip I and other members observe from. Although the sky was darker than it has been, the seeing was poor and became very bad towards the end. Temperatures fell into the upper 40's F, requiring warm clothing but the dew held off until after midnight arrived. Once the moon set, the sky was dark enough for unimpeded views of my favorite objects, galaxies. Along the way I observed a number of planetary nebulae and star clusters too.

The first object I looked for was the supernova underway right now in the face-on spiral galaxy, M-101 in Ursa Major. This type 1A supernova reached a maximum magnitude of 9.9 but has faded to around 10.8 by the time I was able to finally search for it last Saturday night. Unfortunately the glare from the moon and the galaxy's being low in the sky made seeing the galaxy and the supernova harder, but the remains of the exploded star revealed themselves to the west and south of the galaxy's nuclear bulge. It's a pity the supernova didn't appear a few months earlier, it and the galaxy too would have presented a much better view for those who have smaller telescopes.

Comet C/2009PGarrad wasn't hindered at all by the moon, indeed it's tail is more apparent now than the last time I got a good look at it. Now in Hercules it's brighter than before and the tail is more side on from our perspective, making it a nice object for any telescope. A bluish color was evident and the inner coma was very bright, almost like a fuzzy star. The tail was however very diffuse and required averted vision to make out, the comet was also in front of a very star rich backdrop including three bright field stars shining through the tail.


Next I turned the telescope on the Andromeda Galaxy and several of it's companions. Seen here is a drawing I made of the inner region of the closest large spiral galaxy to our own. M-31 is actually about 5 degrees long, far too large to take in all at once through a 15-inch. At 95X the star like nucleus is surrounded by the vast nuclear bulge composed of billions of older yellow and red stars. The inner dust lane was visible plainly as a dark streak amid the intense light from the nuclear bulge and the very diffuse and faint spiral arms of M-31. The spiral arms are easily washed out by light pollution or hazy skies. Just outside the left side of the field of view in the drawing is the dwarf elliptical, M-32. M-110 was also visible on the opposite side of M-31 as a large, oval glow with a weak central brightening whereas M-32 is a small oval with an very bright, almost star like core.

After taking in M-31 and it's two nearly companions I visited two more companions to M-31, the dwarf ellipticals NGC-185 and NGC-147 in Cassiopeia. NGC-185 was bright and had a brighter center, and was easy to spot. NGC-147 was very faint, and took much more effort to spot. Both lie some 250,000 light years from M-31 and 2.7 million light years from Earth, the same distance as M-31 itself.  When I found it, it showed itself as an oval glow larger in apparent size than NGC-185, with a very slight central brightening. The next galaxy I observed in Cassiopeia was the dwarf galaxy IC-10, which is beyond our local group of galaxies. It was visible as a large fuzzy patch with a brighter zone towards one side of it. The light from the stars of the Milky Way in the foreground almost hid it from view.

The next galaxy I observed with the 15-inch was M-33, a face-on spiral galaxy that is considered to be a likely satellite of M-31. Both galaxies are some 600,000 light years apart, and M-33 is some 15 to 20 times less massive than either M-31 or the Milky Way. At 95X the small nuclear bulge is apparent and the surrounding disk is faintly visible, with patchiness and even hints of the spiral structure M-33 is well known for. The huge star forming region NGC-604 was visible, resembling a small dwarf elliptical in orbit around M-33, and a few other smaller and fainter patches where other star forming regions was seen scattered across the galaxy.

After looking at members of our Local Group of galaxies, I turned the 15-inch to Cetus and Sculptor to look at some favorite objects there. The planetary nebula NGC-246 was a large disk through my O-III filter. Despite it's overall magnitude of 8, this large planetary nebula is a difficult object for smaller telescopes, especially when skies are light polluted or hazy without nebula filters. It was very faint without the filter from the airstrip. With the filter in place, brighter zones and darker voids across its face gave the suggestion of a skull, which has led to NGG being nicknamed the "Skull Nebula."

Other objects I looked at were NGC-253, which stretched across the field at 143X and showed darker patches close to the center, and NGC-288, a foreground globular cluster that belongs to the Milky Way. It was resolved into stars to the very center. I also looked for the Cetus spiral galaxy NGC-988, which is behind a star but to no avail.

Another favorite object I looked at was the planetary nebula NGC-7662, also known as the "Blue Snowball." Through the 15-inch at 227X it was about the apparent size of Jupiter, with a very strong blue color and a dark central void visible. I was unable to see the central star due to the very poor seeing that prevailed that night, and it's faintness. Both conspired to hide it amid the glow of the surrounding nebula.

Other objects I observed include the planetary nebulae M-57 and 27, and the globular clusters M-22 in Sagittarius, M-15 in Pegasus, M-71 in Sagitta and NGC-7006 in Delphinus. The galaxies M-74 in Pisces, NGC-891 in Andromeda and the galaxy pair NGC-1160 and 1161 in Perseus were also observed. I stole a few glances at Jupiter, but the seeing was very bad and I couldn't make out much detail on the planet. For a finale, I looked at the Orion Nebula before taking the telescope down and packing up for the trip home.

No comments: