M101, Pinwheel Galaxy, Last Year and This Year

The Pinwheel Galaxy is great to image with my gear because it is just the right size to fill the field of view of my small chip camera at the longest focal length I normally use.  I have a bit of a history with this galaxy in that it is one of the galaxies I tried to image with my old point-and-shoot camera via "afocal" eyepiece projection back when I was first starting.  It looked terrible, but I was thrilled to get the image.  The surface brightness of this galaxy seems a bit low compared to many of the Messiers; maybe that is why it has such a high number.  I imaged it last year with the same gear as this year and was very happy with the result, but now I look at the older image and feel it is overprocessed (too much sharpening, primarily, which brings out detail that is not real).  Both this year's image and last year's are shown below for comparison.  The new image is "deeper," with almost 3 times as much exposure (last year I tried to take multiple images in a night; now, I generally don't try for more than one per session).  In my opinion the colors in the 2014 image are also much better; that's mostly due to improvements in StarTools' color algorithm, I think.

Observing notes:  Light wind gusts again.  Had some trouble getting the mount to settle down and track after doing the goto.  This may be because I started with the scope on the east side of the meridian; I almost always start with it on the west.  I'm using the "lowpass" DEC guiding algorithm again.  Guiding looks like it might be quite good if the wind would settle down.  Hopefully what I'm seeing now is the evening canyon breeze and it will diminish as the night progresses.  After 8 or so subframes, I noticed the connection through the USB-Serial port to the PicGoto had dropped.  I've never seen that happen before without also losing the cameras (because of a loose USB connection), so I got to see what it looks like when you are not guiding at all.  It looks pretty bad with my mount!  Chiller running at 2.5 A, 6 °C on the CCD; it dropped to -2 °C by morning and I had ice all over the outside of the camera.  All in all, despite the wind gusts I was able to keep most of my subframes.  This is significantly better than last year's image, so I'm satisfied, although I'd always love for the image to be sharper.

20.9 ± 1.8 million LY away

From the shape of this galaxy and the streams of stars (particularly along the bottom of the image) I’d guess this guy has undergone at least one collision with another galaxy of significant mass.

Date: 5 Jun 2014
Subject: M101, Pinwheel Galaxy
Scope: AT8IN + HPS Coma Corrector
Filter: None
Mount: CG-5 (Synta motors, PicGoto Simplificado)
Guiding: 9x50 Finder/Guider + DSI Ic + PHD 2.2.2 (Win 7 ASCOM)
Camera: DSI IIc chiller at 2.50 A, 6 to -2.0 °C
Acquisition: Nebulosity 3.2.0, no dither
Exposure: 60x300 s
Stacking: Neb 3, bad pixel map, bias included, normalize first, trans+rot align, 1.5 SD stack.
Processing: StarTools 1.3.5.279 Crop; Wipe:Color & brightness 76%; Develop 90.05%; HDR:Reveal core (for one layer); HDR Optimize soft (for another layer); Color:Scientific, 300% sat.; Deconvolute auto mask 2.5 pix; Track RNC 40.69%; Magic:Shrink 1 pix. CS6 Astronomy Tools layer the “core reveal” layer at 50% transparency on top of the “optimize soft” layer; Healing brush; increase star color; Deep space noise reduction; Less crunchy more fuzzy; Make stars smaller; Astro Frame.

Date: 3 May 2013

Subject: M101, The Pinwheel Galaxy

Scope: AT8IN + HPS Coma Corrector

Filter: None

Mount: CG-5 (Synta motors)

Guiding: 9x50 Finder/Guider + DSI Ic + PHD 1.14.2

Camera: DSI IIc (chiller at ~1.5 A, T = 1.5 °C)

Acquisition: Nebulosity 3.1.5, no dither

Exposure: 21x300 s

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

Processing: StarTools 1.3 Crop; Wipe:Color & Brightness; Develop 95.70%; HDR:Reveal core; Sharpen; Deconvolute: 3.0 pix; Track; Color:Bottom 2.5, Top Full, Sat 650%; Magic:Shrink 1; Life:Moderate.  CS6+Astronomy Tools increase star color; layer mask deep space & space noise reduction; layer mask unsharp mask on dust lanes; less crunchy more fuzzy; make stars smaller; AstroFrame.