Abell 84 is a small, fairly obscure (seldom imaged) planetary nebula, visually located in the constellation Cassiopeia. It was not discovered until 1955, when an astronomer painstakingly examined photographic plates in search of uncataloged planetary nebulae. I suspect that the small, blue star at the center of the nebula is the progenitor star for the nebula.

This pretty nebula is thought to be about 4500 light years from us, and covers about 3.5 arcminutes of the sky; at that distance, Abell 84 is about four-and-a-half light years across.

There are about 9000 stars in the uncropped field, which is slightly larger than a full moon; there are a lot of stars in the sky that we don't see! There are also a LOT of galaxies in the background of the uncropped versions, many showing some structure.

Technical Information:

(HaL)(HaR)(OIIIG)(OIIIB): Ha:OIII:L:R:G:B--690:870:930:180:255:240 (a total of almost 53 hours of exposures); luminance layer consists of blend of 58 fifteen-minute images using a luminance filter, 20 three-minute images using a luminance filter, and 23 thirty-minute images using an Ha filter; R channel is a blend of 12 fifteen-minute images through a red filter, the Ha data also used in the luminance layer; G consists of 17 fifteen-minute images taken through a green filter blended with 29 thirty-minute images taken through an OIII filter, while B is the combination of 12 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 October and November of 2024. Image posted February 15, 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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