Cold December Sky

Mix of Seestar Targets

One month of cloudy weather elapsed since my last Seestar session. Clear moonless evening sky returned in early December bringing cold temperatures. It was nice to sit comfortably inside controlling Seestar when it was 27 degrees outside! I captured no Messier objects over the course of two nights. Instead, a mix of targets presented themselves for observation.

On December 2nd only one annoying neighbor light compromised an otherwise dark sky. I began by targeting the Crescent Nebula, NGC6888, located high above the horizon in Cygnus. A 30-minute exposure with light pollution filter engaged revealed the nebula's oval shape. The brightest star within the oval is a Wolf-Rayet star called WR136 whose strong stellar wind compresses surrounding gas. Ultraviolet radiation from the star causes the gas to glow producing the nebula seen below. WR136, about 21 times more massive than the Sun, has evolved beyond the red supergiant phase. Its high surface temperature creates the ultraviolet radiation which powers the nebula.

Next, I tried to capture a closely spaced group of galaxies in Pisces with a 34-minute exposure. The result was too dim and small to exhibit much detail. There are 3 obvious galaxies in the next picture. From left to right they are NGC474, NGC470, and NGC467. The brightest, somewhat fuzzy object near NGC467 on the right is actually the 7.4 magnitude star HD7991, not a galaxy. When the image is enlarged, two other extremely small and dim galaxies are visible as tiny gray smudges below HD7991. The upper one is 16.6 magnitude galaxy PGC4765. The lower one is 15.5 magnitude galaxy PGC4755. (PGC is the Principal Galaxies Catalog, NGC is the New General Catalog, and HD is the Henry Draper Catalog.)

Pretty open cluster, NGC7686 in Andromeda, was my next target. A 10-minute exposure worked well. Most open clusters show nicely with exposures between 5 and 10 minutes. 

Another good target was open cluster NGC129 in Cassiopeia. Only a 5-minute exposure was sufficient for this one.

The final image from December 2nd revealed dim nebulosity in Cassiopeia near the bright star Gamma Cassiopeiae which appears near the left edge. IC59 is primarily a reflection nebula stretched horizontally across image center. It shows only ghost-like traces in the 55-minute filtered exposure below. IC63 is an arrow-shaped emission nebula to the right of Gamma Cassiopeiae. Both nebulae are being worn away by radiation from Gamma Cassiopeiae. (IC is the Index Catalog, an addition to NGC.)

The next evening, December 3rd, was also clear and cold with 26-degree temperature. No neighbor lights interfered this time. The first target this evening was NGC1931, an open cluster with nebulosity in Auriga. The 45-minute filtered exposure below was able to capture glowing red hydrogen gas surrounding four bright blue stars powering the emission. The four central stars are just barely seen as separate if you click on the following image to enlarge it.

When the original NGC1931 image is enlarged by 150%, however, the four central stars can be seen more clearly separated.

The final image from December 3rd is The Flaming Star Nebula, IC405, in Auriga. In the 50-minute filtered exposure below bright star AE Aurigae is in image center surrounded by glowing gas. Radiation from AE Aurigae causes the gas to glow. While I was amazed to see this nebula gradually revealed by Seestar, I was, once again, disappointed by the washed out red color. Most astrophotos of similar nebulae show a much brighter and deeper red color from excited hydrogen. I still don't know how to correct this problem.

As cold winter weather settles in I'm so happy to watch Seestar perform while sitting warm inside at my dining room table!