Intermediate Spiral Galaxy in Camelopardalis

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NGC2403 is an intermediate spiral galaxy, viaually located within the constellation Camelopardalis. It is about 50,000 light years across (less than half the size of our Milky Way galaxy), and almost 10 million light years away from us. NGC2403 bears a strong resemblance to M33--Both galaxies are about the same size, both harbor immense star-forming regions (the pink areas); and both present to us tilted somewhat, so appear longer than they are wide. The key difference is that NGC2403 is almost four times as far away from us as M33, so is much smaller in apparent size (and hence reveals much less detail).

NGC2403 is perhaps most notable as the first galaxy outside of our Milky Way galaxy in which Edwin Hubble detected Cepheid variable stars, which was instrumental in his proposing Hubble's Law.


Technical Information:

(HaL)(HaR)GB: 480:870:330:210:360 (a total of a bit over 40 hours of exposures); luminance layer consists of blend of 58 fifteen-minute images using a luminance filter, and 16 thirty-minute images using an Ha filter; R channel is a blend of 22 fifteen-minute images using a red filter, and the Ha data also used in the luminance layer; G consists of 14 fifteen-minute images taken through a green filter, while B is the combination of 18 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 (using NormalizeScaleGradient) in Pixinsight. Color combine in Pixinsight. Ha data blended into the luminance and color layers in Pixinsight. Some finish work (background neutralization, color calibration, deconvolution, gradient removal, Multiscale Linear Transform for noise reduction, HDR Multiscale Transform for reducing dynamic range, done in Pixinsight; some finish work (LRGB combination, 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 January and February of 2022. Image posted March 5, 2022.

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

Seeing: Variable, with individual calibrated luminance images having FWHM varying from 1.6 to 2.9 arcseconds.

CCD Chip temperature: -25C

Copyright 2022 Mark de Regt

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