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Perseus Double Cluster

Posted: Thu Nov 19, 2020 5:24 am
by oopfan
aka NGC 869 + NGC 884

William Optics ZenithStar 71 Achromat
Atik 314E Mono CCD
GSO Wratten #12
Optolong Red and Green

W12: 26x60s
R: 70x60s
G: 35x60s

Color Combine:
W12 => L
67% R => R
33% R + 33% G => G
67% G => B

Post-process color calibration not needed due to balanced frame count (planned ahead of time).
Calculated SNR 87 of a magnitude 16.0 star at 3.0" FWHM seeing.

Brian
Perseus-Double-Cluster_W12-26x60s_R-70x60s_G-35x60s_APP_S15-3-25_SA-35-25_G94_NEAT.jpg
Perseus-Double-Cluster_W12-26x60s_R-70x60s_G-35x60s_APP_S15-3-25_SA-35-25_G94_NEAT.jpg (431.35 KiB) Viewed 377 times

Re: Persius Double Cluster

Posted: Thu Nov 19, 2020 9:09 am
by turfpit
Very good Brian.

Dave

Re: Persius Double Cluster

Posted: Thu Nov 19, 2020 1:20 pm
by oopfan
Thanks, Dave.

Something I noticed: The diffraction pattern depends on the filter as can be seen in the attachment. I am certain that this is due to the 2mm thickness of the Newtonian Mask's vanes. Long wavelengths (red) diffract more than short wavelengths (green), so red light does a better job of merging the two edges of a vane into what looks like a single diffraction spike. I'll experiment with a different thickness. At the time I designed the mask I was concerned that a thin vane would tear as I lifted it from the plate.

Brian
Diffraction Pattern of 2mm Vanes.jpg
Diffraction Pattern of 2mm Vanes.jpg (22.45 KiB) Viewed 358 times

Re: Perseus Double Cluster

Posted: Thu Nov 19, 2020 2:10 pm
by umasscrew39
Now that is a stunning image! You need to print that one out and hang it up!!

Bruce

Re: Perseus Double Cluster

Posted: Thu Nov 19, 2020 2:29 pm
by oopfan
Thanks, Bruce, but you know, it never fails, every step forward leads to more head scratching and then refinement. We, I mean "I", never seem to be happy with what I've accomplished. I thank you for your kind words!

Brian

Re: Perseus Double Cluster

Posted: Thu Nov 19, 2020 6:14 pm
by oopfan
Bruce,

I went back and scrutinized my frames and discovered that I was badly out-of-focus in G and W12. Red was excellent. I am to blame. I was racing against the meridian. I usually spend more time when focusing but I was rushed. As it is I had to cut short my W12 run when my scope banged up against the mount. Also, I looked at the stars in my M34 data from last week. The diffraction pattern in G and W12 was just as good as R. So, that is the bottom line: focus.

Brian

Re: Perseus Double Cluster

Posted: Fri Nov 20, 2020 9:32 pm
by umasscrew39
Thanks for the update, Brian. Well, we have all rushed at times and failed to focus or especially refocus as needed. I am guilty of that for sure. Glad you sorted it out.