Ced 214 (including [?] NGC 7822) is a large emission nebula in the constellation of Cepheus.
This is another entry in the quot;shot a while ago, wanted to redo with better equipment,quot; but this one turned out worse than the
old shot. There should be a lot of dark nebulas traversing this nebula, but the contrast must have gotten lost because I was shooting this with a simple luminance filter rather than the appropriate H-alpha filter. More on this below if you care.
Technical details:
Date: Aug 7, 2016
Time: 1:30 pm - 2:40 am
Camera: SBIG STF-8300M
CCD Temperature: -5 C
Optics: Televue 127is (native)
Filter: AstroDon L
Light frames: 7x8 min
Dark frames: 16
Flat frames: 50
Flat darks: 50
Binning: 1x1
Guiding: Orion SSAG @ Orion finder (~162 mm)
Mount: AP Mach 1
Dithering: Manual
Processing: Stacking and deconvolution in CCDStack, Curves, Levels in PSCS6.
Other notes:
As soon as the first image showed up on my screen I could tell that this would not produce the image I had in mind. I had the choice between sticking to my plan (stay out until 4:40 am to get a lousy image), or turn this into an exploratory shot to determine if I can process a smaller number of frames.
The deal is this. The luminance filter transmits all wavelengths. To get a bright image, you expose for x minutes. The H-alpha filter only transmits a narrow wavelength range, so to get a bright image, you will need to expose for ~2x minutes. If the number of dark hours in one night is fixed, you have the choice. (1) Luminance filter, collect N frames or (2) H-alpha filter and collect ~N/2 frames. The issue with fewer frames is that you have fewer statistics for noise rejection (airplanes, asteroids, ...). While I typically aim for 20+ frames, I have never explored just how bad the image looks with far fewer (~10) frames. This exploratory shot explored that limit. With just 7 frames, I think the background noise is fine.
Now that I have determined that, I can reshoot this target with the H-alpha filter, longer exposure time, fewer frames, and I should get something that will blow this image out of the water.
