Short Cold Night at Harvard

The December 8 forecast was to be in around 32 by 9PM I decided to keep the night short. Astro-twilight was about 6:05 PM so I  arrived at the town of Harvard parking dark site around 4:30PM. Setup and all star polar alignment went smoothly. I deviated from the original target list dropping  M31 and NGC 1342 while adding M77 and NGC 2024. I probably should have stuck with NGC1342 instead of M77 which would be better imaged at a longer focal length. A combination of the dew hood and an ~8 mph breeze from the north challenged the auto-guider. And, having forgotten to bring my balaclava head covering the wind chill challenged my face during tear down at the end of the night. Fortunately I did remember to bring gloves and hand warmers. The five targets imaged appear below. Additional notes follow the images.

IC 5146

M33 (Triangulum Galaxy)

Messier 77(NGC 1068)

NGC663

NGC2024 (Flame Nebula)

All imaging was done at F/4 (800mm) with Celestron 8 AVX + Starizona Night Owl focal reducer corrector + ZWO ASI294MC Pro. Image area reduced to 3104x2116 pixels. Imaging temperature -10C. Of note, optical configuration was kept assembled and dark frames acquired the following day. Processing was with Autostakkert! I decided to experiment with acquiring dark frames with camera rotated slightly clockwise and counterclockwise from original. These were found to have little effect on post processing. For this reason I will likely acquire flat frames after the night of imaging with a reassembled optical configuration. I'll also return to the Orchard site which has less of an issue with passing cars.

Comet C2017T2, IC405, IC410, M33, NGC281, M42, NGC7635

Here are a few recent images acquired this 2019 winter. All were acquired at F/4 using the recently with Celestron 8+Starizona Night Owl FR+Orion SkyGlow Astrophotography filter. Camera: ZWO ASI294MC Pro, Mount: Celestron Advanced VX, Guider: Orion Magnificent Mini Autoguider. 

Look closely at Comet C2017T2 and you might notice the glow slanting down to its left. That's residual glow not zeroed out by the flat frame. Vignetting from the Night Owl is very aggressive and tough to zero out.  

Using SharpCap 3.2 I have found collecting flat frames at a narrow range of different exposures that give a histogram just above and below the "above 20%" criterion should provide a flat frame that does a good job zeroing out vignetting and artifacts. *

* More recently I have found a 20% to 80% histogram range, as recommended by SharpCap documentation works best. 

Update:03/13/2025 M33 reprocessed 

Comet C2017T2 PANSTARRS -- 15x60s @bin2

IC410 -- 6x300s @bin1

M33 (180s exposures)

IC405 -- 6x300s @ bin1

NGC281 -- 10x180s @bin1

M42 -- 25x8s @bin1

NGC7635 -- 6x300s @ Bin1