Sharpless 116 is a small emission nebula (formerly believed to be a planetary nebula, but a more recent study documented low levels of OIII emissions, indicating it's not a planetary nebula), part of the much larger emission nebula Sh2-115, which surrounds it in this image (and, more evidently, in the uncropped versions).

This area is about 7500 light years from us; at that distance, Sh2-116 is about six light years across.

Most of the emission nebulae that I image can be successfully processed in a number of ways, each of which is pretty and interesting. Because of the paucity of OIII and SII in this entire region, none of the other ways I processed the data was interesting to me, so I did not post any. I did weave some of the OIII and SII data into the color layer of this image.

The processing of this data set was immensely complicated by my needing to send my camera/filter wheel/AO-X back to SBIG for repair before I had gathered enough data. This necessitated taking another set of flats for the later images taken after the return of the camera assembly.

Technical Information:

(HaL)(HaSIIR)(OIIIG)(OIIIB): Ha:OIII:SII:L:R:G:B--660:720:630:555:120:135:280 (a total of almost 52 hours of exposures); luminance layer consists of blend of 33 fifteen-minute images using a luminance filter, 20 three-minute images using a luminance filter, and 22 thirty-minute images using an Ha filter; R channel is a blend of 8 fifteen-minute images through a red filter, the Ha data also used in the luminance layer, and 21 thirty-minute images taken through an SII filter; G consists of 9 fifteen-minute images taken through a green filter blended with 24 thirty-minute images taken through an OIII filter, while B is the combination of 14 twenty-minute images taken through a blue filter blended with the OIII data.

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. Narrow-band data blended into the luminance and color layers in Pixinsight. Some finish work (GradientCorrection, background neutralization, color calibration, NoiseXTerminator, BlurXTerminator, 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 June, July, August, October and November of 2024. Image posted February 10, 2025.

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

Seeing: Variable, with individual calibrated luminance images having FWHM varying from 1.9 to 3.2 arcseconds.

CCD Chip temperature: -25C

Copyright 2024, 2025 Mark de Regt

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