Barred Spiral Galaxy in Ursa Major

Click here for different-resolution, uncropped versions:  40% (1638x1638)  65% (2662x2662) 100% (4096x4096)


Messier 109 is a very large barred spiral galaxy, located very near one of the bright stars in the bowl part of the Big Dipper (the source of the blue glow in the left of the uncropped image). M109 is estimated to be about 83 million light years away from us; at that distance, it is about 175,000 light years in diameter (somewhat larger than our Milky Way, itself a large galaxy). It is thought to contain a trillion (that's a thousand billion; or a million million) stars! Because of its great distance from us, it covers a very small patch of the sky--only 7.6 arcminutes in diameter (by comparison, a full moon is about 30 arcminutes in diameter). For comparison, M33 is a bright, splashy galxy in our local group of galaxies; in my linked photo, it appears very large and bright. But that's because it's only 2.7 million light years away (3.2% as far as M109); in fact, it is about 1/3 the diameter of M109, with about 4% as many stars as has M109.

As usual in a deep-sky image, there are a lot of small (meaning distant) galaxies in the uncropped versions of the image (look for the oblong and/or fuzzy "stars"). Unusually, there are several fairly large "small" galaxies in the background of this image. In particular, to the right of the M109 are three significant (in apparent size) galaxies, UGC 6969, UGC 6940 and UGC 6923 (from bottom to top; only the first two in the cropped version now displaying). It is thought that these three may be satellite galaxies of M109.


Technical Information:

L:R:G:B: 510:240:210:280 (a total of almost 21 hours of light-frame exposure time); luminance was a blend of 15-minute images and 5-minute images; red and green exposures were all 15-minute exposures; blue all 20-minute exposures. After discovering that my mirror looked like it had been on the wrong end of a mudslide, I cleaned it and re-took the luminance images (and did not use any of the earlier luminance data).

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.

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, deconvolution, multiscale linear transform, HDR multiscale transform, and noise reduction) done in Pixinsight; some cleanup finish work was done in Photoshop CC.

Location: Data acquired remotely from Sierra Remote Observatories, Auberry, California, USA.

Date: Images taken on many nights in March, April and May of 2022. Image posted June 13, 2022.

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

Seeing: Generally good; luminance images varied in FWHM from 1.7 to 2.8 arcseconds; luminance master was deconvolved to 2.1 arcsecond FWHM.

CCD Chip temperature: -25C

Copyright 2022 Mark de Regt

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