Thursday, September 19, 2013

NGC 281 HaRGB

NGC 281 HaRGB by S Migol
NGC 281 HaRGB, a photo by S Migol on Flickr.
Via Flickr:
NGC 281 HaRGB in Menlo Park, CA Sept 2013


The RGB data came from sessions over 3 nights in variable conditions. I had to be aggressive in trimming the bad subexposures. I was also adjusting the flattener position during these sessions, leading to strange star images on the edge.

The Ha data came from Sept 15 with a past-first quarter moon blazing in the sky. The filter used is a 35nm wide filter, letting a fair amount of light through. The dark part of the sky in this set was pretty noisy.

Standard setup: Stellarvue SV4 scope with the modified and cooled Pentax K10D camera. Standard sub length of 1200 seconds at 100 ISO.

RGB: 18 total frames at 1200 seconds for 6 horus of integration.
Ha: 6 frames at 1200 seconds for 2 hours of integration.

Calibrated in Maxim (one set of RGB data had bad flats with moving dust motes)
Stacked in DSS (RGB and Ha stacked separately)
RGB and Ha registered in PixInsight via StarAlign.
Dead pixels in Ha were cleaned up.
Ha was run through TGVDenoise to improve the background a bit before merging via NBRGB script.
DBE on merged output. Masked stretch, Histogram stretch, MT, and TGVDenoise again to fix noisy background. Masked curves to drive background lower and boost midrange. Final step was to fix the dust motes from bad flats.

Here is the platesolve from PI:
Referentiation Matrix (Gnomonic projection = Matrix * Coords[x,y]):
-1.20093e-005 +0.000530235 -0.619397
-0.000530057 -1.20479e-005 +0.993858
+0 +0 +1
Projection origin.. [1847.500040 1209.999936]pix -> [RA:+00 52 00.19 Dec:+56 43 04.19]
Resolution ........ 1.909 arcsec/pix
Rotation .......... -88.710 deg
Focal ............. 648.29 mm
Pixel size ........ 6.00 um
Field of view ..... 1d 57' 33.8" x 1d 16' 59.8"
Image center ...... RA: 00 52 00.186 Dec: +56 43 04.19
Image bounds:
top-left ....... RA: 00 47 21.980 Dec: +57 42 22.66
top-right ...... RA: 00 47 17.187 Dec: +55 44 51.27
bottom-left .... RA: 00 56 58.081 Dec: +57 40 34.92
bottom-right ... RA: 00 56 24.072 Dec: +55 43 08.99