First light image with the HPS coma corrector. The Deer Lick Group was easy to find tonight with the Telrad. It helps that I have now oriented the guide scope to match the orientation of the imaging scope; I was able to pick up the pattern right away. Weather conditions are excellent: clear, very little wind, much cooler than it has been. CCD is at ~5 °C to start, but dropped to -1 °C at the end, so there was a lot of temperature variation during the night. The coma corrector does seem to be giving nicely round stars across the whole field of view. When I performed the meridian flip, I noticed the camera gain was set at only 83% (from earlier today when I was dialing in the coma corrector), so this will mess up the calibration of those subs. Set it back at 100% for the flipped images. So a lot went wrong with this, but the coma corrector does seem to help keep the stars round.

In the 2nd & 3rd revision, I included in the stack only the frames where the camera gain was set to 100% (33x300 sec), and processed two layers, one for resolution and one for noise suppression, then put them together with a Gaussian blurred layer mask. Enhanced star color. Used Astronomy Tools Enhance DSO/Reduce Stars. Finally, I had quite a bit of green and blue stuff I’m sure was noise, so I did a color range selection on it, created a saturation adjustment layer, and desaturated those pixels. I think this looks better.

In the 4th revision, I used all 59 subframes (59x300 sec) but did a lot less stretching and did not use layer masks. I fiddled with the color balance a bit as the original data were too blue. I think I like this last one the best.

In the 5th revision, I re-stacked using a bad pixel map with bias subtracted (I just learned that I needed to remove bias when using a BPM). Processing was with StarTools with a heavy stretch and extensive sharpening, finishing with Life:Less=More. Layer mask noise reduction in CS6. Best yet.

Date: 12 Sep 2012

Subject: NGC 7331, Deer Lick Galaxy Group

Scope: AT8IN+High Point Scientific Coma Corrector

Filter: None

Mount: CG-5 (Synta motors)

Guiding: Orion ST80 + 0.5x Antares telereducer + DSI Ic + PHD

Camera: DSI IIc (cooled at 2 A, 7.5 V, 5 to -1.5 °C)

Acquisition: Nebulosity 3.1.1

Exposure: 59 x 300 s

Stacking: Neb 3, bias included, normalize first, trans+rot align, 1.5 SD stack