NGC 5746, the galaxy to the left of the image, is a barred spiral galaxy visually located
in the constellation Virgo. It presents to us almost edge-on. It is thought to be about 95 million light years away from us, which would give it a diameter of about 230,000 light years
(a very large galaxy; about twice the diameter of our Milky Galaxy, which is a large galaxy). The width of the image is about 30% more than the angular size of a full moon. Technical Information: L:R:G:B: 690:255:195:320 (a total of over 24 hours of light-frame exposure time); here's a chart showing the various subexposures I used in the image (I
also took a set of images through the Ha filter, but did not use them, as there do not seem to be appreciable Ha emissions in this galaxy from our angle: 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), 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, combined and cropped in Pixinsight. Color combine in Pixinsight. Some finish work (background neutralization,
color calibration, NB blend, NoiseXTerminator and BlurXTerminator) done in Pixinsight; some cleanup finish work was done in Photoshop 2024. Location: Data acquired remotely from Sierra Remote Observatories, Auberry, California, USA. Date: Images taken on many nights in March, April and May of 2025. Image posted August 30, 2025. Date: Image scale of full-resolution image: 0.56 arcseconds per pixel. Seeing: Generally good. CCD Chip temperature: -25C Copyright 2025
Mark de Regt
The galaxy to the right of the image is NGC 5740, a barred spiral galaxy showing a lot of structure; it is thought to be about 72 million light years from us. At that distance,
it would be about 76,000 light years across, a fairly large galaxy.
These two large galaxies are far apart, in cosmic terms; they just appear in the same field of view.
The blue glow at the bottom left of the image is from a magnitude 3.7 star that dominates the lower half of the uncropped image. So I cropped out most of the lower half of the image,
since I did not feel that the image looked very good uncropped.
As is often the case with large-field deep-sky photographs, there are a lot of tiny (meaning, of course, very far away) galaxies in the background of this photo; they're very evident in
the full resolution version, with many of them large enough to show significant structure.
If you look carefully, you will notice that the bulge in the middle of NGC 5746 is flat on the top and bottom. This is not an illusion or processing artifact; it is the bulge of
the galaxy's bar, from the side. I think this is really cool!
Luminance: 42 fifteen-minute and 20 three-minute
Red: 17 fifteen-minute
Green: 13 fifteen-minute
Blue: 16 twenty-minute
Luminance layer is a blend of the two sets of luminance-filtered images.
Red is entirely the red-filtered images.
Green is entirely the green-filtered images.
Blue is entirely the blue-filtered images.