Sharpless 140
Emission Nebula in Cepheus

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Sharpless 140 is an emission nebula/star-forming region visually located in the constellation Cepheus. The red parts of the image are the emissions of ionized hydrogen, resulting from the highly energetic massive new stars recently formed in the region. The dark part in the lower half of the image is LDN 1204 (1204 in the catalog named Lynd's Dark Nebulae), a dust cloud obscuring light from reaching us from the far side of the nebula. This region is very similar to the area in this image, in that it is primarily composed of an obscuring dark nebula between us and a bright emission nebula.

The glow in the upper right corner is from a very bright star, just off the frame. And, no, those darker blobs in the dark nebula aren't places where the flat field correction failed; they're structure that's there.

This area is about 2900 light years from us. At that distance, the emission nebula shown is about 32 light years across.


Technical Information:

(HaL)(HaR)GB: 1020:495:180:150:180:200 (a total of a bit over 34 hours of exposures); luminance layer consists of blend of 33 fifteen-minute images using a luminance filter and 34 thirty-minute images using an Ha filter; R channel is a blend of Ha data also used in the luminance layer and 12 fifteen-minute images using a red filter; G consists of 10 fifteen-minute images taken through a green filter, while B is the combination of 10 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. Ha data blended into the luminance and color layers in Pixinsight. Some finish work (background neutralization, color calibration, deconvolution (Blur XTerminator), gradient removal, Noise XTerminator for noise reduction, 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 September and October of 2023. Image posted April 22, 2024.

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 2.4 arcseconds.

CCD Chip temperature: -25C

Copyright 2023, 2024 Mark de Regt

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