Abell 2666 is a small galaxy cluster, centered about 340 million light years from us. One can distinguish the distant galaxies from the foreground stars (stars close to us in our own galaxy) by noting whether it is perfectly round, and by whether it is quite compact (the galaxies have a fuzzier edge). Abell 2666 is thought to contain 32 galaxies, an unusual percentage of which are spiral galaxies. The largest galaxy in the image, to the right of center in this image, is NGC 7768, a large elliptical galaxy thought to be 369 million light years away. The uncropped image shows a surprising amount of detail in some of the galaxies; I particularly like the tidal tail on the galaxy near the left edge of this image, and the barred-spiral galaxy just left of NGC 7768.

I always enjoy looking at the small background galaxies in many of my images. This one is especially fun that way, with a great number throughout the uncropped image.

The entire field of the uncropped version of the photo is about the same width as a full moon.

Technical Information:

LRGB: 531:195:180:260 (a total of over 19 hours of exposures); luminance layer consists of blend of 31 twenty-minute images 22 three-minute images (all using a luminance filter); R channel is a combination of 13 fifteen-minute images taken through a red filter; G consists of 12 fifteen-minute images taken through a green filter, while B is the combination of 13 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 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, Noise XTerminater, Blur XTerminator) done in Pixinsight; some finish work (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 October and November of 2025. Image posted February 20, 2026.

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

Seeing: Variable

CCD Chip temperature: -25C

Copyright 2025, 2026 Mark de Regt

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