Barred Spiral Galaxy in Triangulum

Click here for other versions: full resolution cropped (2473x2473)  50% uncropped (2024x2027)  100% uncropped (4048x4054)


NGC925 is a barred spiral galaxy high in the nothern sky in late summer, into the winter, about 30 million light years from us. It has only a loosely-wound spiral structure, with the arm on one side being distinctly more pronounced than the arm on the other side; it is thought that this may be the result of a collision between NGC925 and another galaxy. It has a diameter of about 95,000 light years (a good-sized galaxy, but smaller than our Milky Way).

The galaxy is tilted 55 degrees from us, so that it looks more elliptical than it is. The pink blobs strewn about the galaxy's arms are areas of intense star formation, in which hydrogen gas has been ionized by the new, energetic stars.

The entire field of the uncropped version of the photo is about the same width as a full moon. As always, it's fun to examine the full resolution, uncropped version to find background galaxies, hundreds of millions of light years away.


Technical Information:

(HaL)(HaR)GB: 420:660:255:180:220 (a total of almost 29 hours of exposures); luminance layer consists of blend of 44 fifteen-minute images using a luminance filter and 21 twenty-minute images using an Ha filter; R channel is a blend of 17 fifteen-minute images taken through a red filter and the Ha data; G consists of 12 fifteen-minute images taken through a green filter, while B is the combination of 11 twenty-minute images taken through a blue filter.

Equipment: RC Optical Systems 14.5 inch Ritchey-Chrétien carbon fiber truss telescope, with ion-milled optics and RCOS field flattener, at about f/9, and an SBIG STX-16803 with internal filter wheel (SBIG filter set), guided by an SBIG AO-X/STX Guider, 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, gradient removal, HDR Multiscale Transform, Multiscale Linear Transform for noise reduction and sharpening, and blending the Ha data with the broadband data) done in Pixinsight; some finish work (Neat Image noise reduction, LRGB combination, contrast and saturation adjustment) was done in Photoshop CC.

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

Date: Images taken on many nights during October and November of 2021. Image posted December 12, 2021.

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

Seeing: Generally very good, with individual luminance images having FWHM varying from 1.6 to 2.2 arcseconds.

CCD Chip temperature: -25C

Copyright 2021 Mark de Regt

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