Clear October Sky

 Long Exposures

October usually offers periods of clear sky for astronomy. October 6-7 was one such night. I tried a long exposure of the Andromeda Galaxy, M31, hoping to capture dust lanes not well visible in a previous 68-minute exposure. Seestar operated for about 8.5 hours from 7:50 pm EDT to 4:20 am EDT to produce the following image using equatorial mode and mosaic mode. This image is a 320-minute (5 hour 20 minute) effective exposure produced by stacking 1920 10-second subframes. Only 60 subframes were rejected due to tracking errors. The sky became hazy for a while during the exposure before eventually clearing. Although some outer dust lanes are visible, other faint features did not stand out well above the background sky. 

I processed the M31 image differently to make outer dust lanes more visible, but this came at the expense of making background sky foggy instead of dark. The following image shows the result. Some sky fog features may have been caused by neighboring lights turning on and off during the exposure. Anything done to reduce background fog also immediately removed faint galaxy features. There's no escape from consequences of my imperfect observing location.

The next night, October 7-8, was clear again! The Pinwheel Galaxy, M33, was well placed in the constellation Triangulum. Seestar operated for about 9 hours 50 minutes to produce the following 380-minute (6 hour 20 minute) exposure. 2280 10-second subframes were stacked with 40 rejected. Seestar used EQ mode, mosaic mode, and no light pollution filter. This image improves upon a previous 80-minute exposure and reveals more faint details in the outer galactic arms. 

Another clear sky opportunity arose on October 13-14. This time my target was NGC7635, The Bubble Nebula in the constellation Cassiopeia. Seestar operated in EQ mode with light pollution filter engaged for only about 6 hours 15 minutes because I halted the exposure when clouds moved in. Unfortunately, as I was bringing equipment inside, the clouds disappeared and remained absent until dawn! So, I could have produced a longer exposure if I had been patient.

The following 288-minute (4 hour 44 minute) exposure consists of 1704 stacked 10-second exposures with only 42 rejected. The rejections probably happened during the brief cloudy period. The bubble is created by the interaction of a strong stellar wind from the hot (37,000K surface), 45 solar mass star SAO 20575 with nearby gases. SAO 20575 is the bright off-center star near the white top of the bubble. The denser gas cloud on one edge resists expansion keeping SAO 20575 off center. Details in this image are better than in a previous 45-minute exposure. 

Five days later on October 18-19 another good cloudless sky appeared, although darkness was spoiled by the presence of a first quarter Moon. My target this time was IC1805, The Heart Nebula in Cassiopia. Seestar operated for nine hours to produce the following 364-minute (6 hours 4 minutes) exposure. It consists of 2185 stacked 10-second subframes with only one rejected. I used mosaic mode, equatorial mode, and the light pollution filter. This image shows much more detail than a previous 60-minute exposure. 

My new Seestar 50 Pro will arrive in a few days. I'm looking forward to exploring the new features and getting even better images.