Spiral Galaxy in Pegasus

Click here for different resolutions (all uncropped, unlike the photo below):  40% (1638x1638)  65% (2662x2662)  100% (4096x4096)


NGC7331 is a non-barred spiral galaxy in Pegasus, presenting to us almost edge on. It is generally estimated to be about 40 million light years from Earth. It is perhaps 120,000 light years in diameter, similar to our Milky Way galaxy (it is thought to be very similar to our Milky Way galaxy in many ways, other than not having a bar).

Note there are a number of other galaxies in the picture close to NGC7331, highlighted by the four just above NGC7331 in the photo; these four, together with NGC7331, are called "The Deer Lick Group," supposedly "in commemoration of one of the finest nights of viewing EVER, at Deer Lick Gap, just off the Blue Ridge Parkway, in the NC mountains," by persons unnamed. All the other galaxies are hundreds of millions of light years away from us, and not in any way (other than visually) connected to NGC7331.

This is the second time I have imaged this target. I had imaged it twenty years earlier from my yard. If you want to compare that image to this one (to see what much darker skies, better equipment, and (hopefully) more skill can do, click here.


Technical Information:

LRGB: 525:180:180:240 (almost 19 hours of exposure time on the keepers; L, R and G each comprosed of 15-minute images; B comprised of 20-minute images; all images unbinned).

Equipment: RC Optical Systems 14.5 inch Ritchey-Chretien carbon fiber truss telescope, with ion-milled optics and RCOS field flattener, at about f/9, and an SBIG STX-16803 camera with internal filter wheel (SBIG filter set), guided by an SBIG AO-X, all riding on a Bisque Paramount ME German Equatorial Mount.

Image Acquisition/Camera Control: Maxim DL, controlled with ACP Expert/Scheduler, working in concert with TheSky X Professional Edition.

Processing: All images calibrated (darks, bias and sky flats), aligned and combined in Pixinsight. Color combine in Pixinsight. Some finish work (background neutralization, color calibration, HDR combine/HDR Mulitscale Transform and deconvolution of luminance data and noise reduction) done in Pixinsight; some cleanup finish work was done in Photoshop CC.

Location: Data acquired remotely with my equipment hosted by Sierra Remote Observatories, Auberry, California, USA.

Date: Images taken on many nights in October, November and December of 2020, and August 2021. Image posted September 5, 2021.

Date: Image scale of full-resolution image: 0.56 arcseconds per pixel.

Seeing: Generally ok, with individual calibrated luminance frames varying from 1.7 to 2.3 arcsecond FWHM.

CCD Chip temperature: -25C

Copyright 2020, 2021 Mark de Regt

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