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By Davide Simonetti
The Crab Nebula (also known as M1, NGC 1952 or Taurus A). This is quite an improvement on the last attempt at imaging M1 about two years ago. This time it was possible to bring out some of the filaments that make this object so interesting - this despite using a much shorter focal length making the object appear significantly smaller. The image is cropped rather radically to show more details in the nebula so the stars appear bigger than I would prefer, but on the original they look fine.
040 x 300 second exposures at Unity Gain (139) cooled to -20°C
050 x dark frames
040 x flat frames
100 x bias frames
Total integration time = 3 hours and 20 minutes
Captured with APT
Guided with PHD2
Processed in Nebulosity, Fitsworks, and Photoshop
Telescope: Sky-Watcher Explorer-150PDS
Mount: Skywatcher EQ5
Guide Scope: Orion 50mm Mini
Guiding Camera: ZWO ASI120MC
Imaging Camera: ZWO ASI1600MC Pro
Baader Mark-III MPCC Coma Corrector
Light pollution filter
I got back yesterday from AstroFest and,what do you know, it was clear outside!
Just had to go with what was set up at the time:
Quattro 8" with Coma Corrector Avalon M-Uno Atik 460EX ZWO OAG (first real time I've used an OAG) with SX Ultrastar Baader 7nm Ha The OAG proved easy enough to use with decent star images, and I wanted to try it quickly on a number of targets. So here we have:
M1, 12x5 minutes (oops, forgot to dither) Horsehead and Flame , 4x5 minutes (ditto) Flaming Star, 6x5 minutes, to continue the flame theme (did remember to set up dithering in Nebulosity) ...all with no cropping, so same FOV.
Certainly not the greatest of pictures, and only very quick processing, but I hope not too bad for such short exposures in Ha. I'm really starting to think that I prefer just mono or RGB because it all happens so much more quickly (and it went down to -2C last night here... OK, not Pyeongchan, but quite chilly enough.)
I have been using a 1 1/4 inch UHC filter but this had been causing bad vignetting that was difficult to remove during processing. So, I left out the filter so there was a 'straight 2"' opening into the camera. However, the light pollution meant that 45 s was the maximum exposure. Anyway, I took 65 x 45s of Orion and 165 x 45 s of the Crab - one looks good (for me ) and one looks bad, even for me ! I tried the processing several times but this was the best I could do.
So, the advice I am after is, is the poor image of the crab due to the nature of the nebula? my camera is unmodded.