October Clear Spell

Long Exposures

October usually brings periods of clear sky. This year the clear spell happened near new Moon, so bright moonlight did not interfere with attempts to try long exposures of nebulae with Seestar. On October 15th, using mosaic mode and light pollution filter, I made a 111-minute exposure of IC1848 - the Soul Nebula in Cassiopeia. The next image shows the result. The nebula's brighter parts are visible, but, compared with online photos made with better equipment, much of the dimmer portions are missing. (Enlarge the image by clicking on it to get the best view.) 

A few days later on October 20th I made a 110-minute unfiltered mosaic exposure of the Pleiades. Fine detail in the wispy blue reflection nebulae can be seen in the next picture. This year's Pleiades image is much better than last year's result made without mosaic mode and without Seestar's AI Denoise feature.

Two nights later on October 22nd clear moonless sky presented another imaging opportunity. This night I began with a 130-minute filtered exposure of the California Nebula (NGC1499) in Perseus. This is the longest Seestar exposure I've ever made. Mosaic mode was necessary to capture the nearly two-degree length of this nebula. The next image shows the bright outline of "California", but the dimmer central part of the nebula is missing.

I think dim nebulae portions don't show up in these long mosaic exposures for two reasons. First, each constituent part of the final mosaic is not exposed for the full time as Seestar moves from one position to another to cover the entire area. Second, my relatively bright light polluted sky makes it difficult for dim features to rise above background glow. 

Past midnight on October 22nd I saw Orion rising above trees. Troublesome neighbor lights were all turned off at this time, and dark conditions were too good to pass up. So, I set Seestar to make a filtered mosaic image of the Horse Head Nebula (IC434), the Flame Nebula (NGC2024), and the bright star Alnitak in Orion's belt. The next 71-minute exposure shows more detail than my previous attempt last year. It would have been nice to expose for more than 71 minutes, but at 3am my sleep deprived brain shut down, and I went to bed.

After gaining experience using long exposure mosaic mode, I've discovered that subsequent processing with AI Denoise seems to eliminate artifacts caused by field rotation. As usual, Seestar's reported exposure time is much less than the actual exposure time because so many frames are dropped due to tracking errors. This means I need to plug Seestar into external power to prevent the battery from running out while it runs nearly all evening to make one image.