Hidden Galaxy
Spiral Galaxy in Camelopardalis

Click here for higher-resolution versions: 40% (1444x1532) 65% (2347x2457) 100% (3611x3781)
Click on image to toggle between the version with blue extinction, and a version of what it might look like were there not a huge amount of dust between the galaxy and us


IC342 is a large grand design spiral galaxy, quite close to us (in cosmic terms) at only about 10 million light years distant. It appears camouflaged among a dense star field, because its light passes through the plane of our Milky Way galaxy in order to reach us. All the intervening stars (all the individual stars you see in this photo are foreground stars in our own galaxy) and gas/dust attenuates the light a great deal, and because red light survives such a journey better than blue light, the entire galaxy takes on a reddish tone. Were it not obscured by all that dust in our galaxy, IC342 would be visible to the naked eye in dark skies (the most distant celestial object that would be so visible).

The pink regions (of which there are many) are star-forming regions; it is thought that this beautiful galaxy may have undergone a burst of star formation recently (like 60 million years ago; "recent" and "close" have different meanings in cosmic terms!).

There appears to be a bit of a bar at the center of the galaxy; there is thought that IC342 is evolving into a barred spiral galaxy.

The entire field of the photo is about the same width as a full moon. The galaxy has a diameter of about 70,000 light years, and contains about 100 billion stars (both numbers are less than our Milky Way galaxy).

I have presented this galaxy in two ways: (i) Showing it in the colors that reach us, reflecting the extinction of much of the blue signal (thereby shifting the image of the galaxy--but not the foreground stars, which are much closer--toward red), and (ii) showing it as it might look from outside the plane of our galaxy, with more blue (accomplished by lowering the color temperature of just the galaxy). Click on the image to toggle between the two versions.


Technical Information:

(HaL)(HaR)GB: 450:1170:225:300:240 (a total of almost 40 hours of exposures); luminance layer consists of blend of 30 fifteen-minute images using a luminance filter, 24 thirty-minute images through the luminance filter, and 15 thirty-minute images using an Ha filter; R channel is a blend of the Ha data and 15 fifteen-minute images taken through a red filter; G consists of 20 fifteen-minute images taken through a green filter, while B is the combination of 12 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 for noise reduction and sharpening, and blending the Ha data into the red channel and the luminance layer) 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 August, September and October of 2021. Image posted October 17, 2021.

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

Seeing: Excellent

CCD Chip temperature: -25C

Copyright 2021 Mark de Regt

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