Thursday, November 10, 2016

Large Stack Experiment--M33, M31, NGC6912

Despite a half moon, skies were steady and transparent last night, with still conditions, making it a good night to try some more stacking experiments. The setup was my ZEQ 25 mount, f/4 Newt, and DS16C imager; no filters were used. I upgraded to the latest version of the MallincamSky software, but I was unable to get the dark field capture to work. However, the DS16C is very low noise, so I decided to go ahead and do the experiments anyway. Given that there is no noise correction of any kind, the images are remarkably low noise with little amp glow visible.

Image capture parameters were: Gain: 18; Exposure: 19 seconds; auto white balance. Histogram upper end was 100, lower end varied between 10 and 15, depending on the image.

Stack sizes were:

M33: 2x99-image stacks combined in Nebulosity
M31: 99 images
NGC6912: 99 images

Noise stacking artifacts are visible on the M33 image; the M31 image shows very minor improvement over the smaller stack I captured last Friday (a little more dust lane detail is visible above the center of the image), suggesting about 25-35 images is the "sweet spot" for good S/N in skies with moderate skyglow.