This was a first-time observation of this galaxy, and the first time in a long time I have used my coma corrector (mainly because I wanted the smallest image scale I could get); it was the first time ever to use the coma corrector while controlling the session with Sequence Generator Pro. I had lots of trouble getting plate solves to work with this combination. I think it was a combination of having the wrong imaging scale (apparently PlateSolve2 is pretty sensitive to that, but eventually I used nova.astrometry.net to do a successful blind solve and got the scale), not having enough stars (I had to increase the length of my plate solve exposures), and being out of focus some of the time (focus was definitely drifting, and I think the image plane may not have been perfectly perpendicular to the optical axis). However, eventually I got it all working and got some data before the clouds thickened too much. I think there were some thin high clouds throughout the session. This is an image that looks better if you don’t look too close! Next time I'm going to try a different set of spacers and hopefully get the imaging plane squared away.

Date: 2 Mar 2016

Subject: NGC 2841, spiral galaxy in Ursa Major

Scope: AT8IN + High Point Scientific 2” Coma Corrector

Filter: Baader Planetarium UHC-S

Mount: EQ-6 (EQMOD)

Guiding: Orion ST-80 + Antares 0.5x focal reducer + DSI Ic + PHD 2.6.1.1 (Win 7 ASCOM)

Camera: DSI IIc, no chiller CCD 9 °C

Acquisition: Sequence Generator Pro 2.4.3.25 with Nebulosity 4.0.4 ASCOM camera driver

Exposure: 18x600 s

Stacking: Neb 4, bad pixel map, bias included, 33 flats, CMYG nebula filter, match histograms, trans+rot align, Nebulosity 40-60tile stack.

Processing: StarTools 1.4.305: Crop; Wipe; Develop: 84.80%; HDRptimize; Color:Scientific, 200% saturation; Deconvolute: 2.8 pix; Track: Smoothness 87%, 5.5 pix; Magic, shrink 2 pix. Photoshop CS6 + Astronomy Tools: Deep space noise reduction; Increase star color; Make stars smaller; several cycles of layer-masked Levels to reduce halo around bright star; Astroframe