Abell 2218
Abell 2218
Huge Galaxy Cluster in Draco

Click here for higher-resolution versions: 40% (1592x1596) 65% (2588x2595) 100% (3981x3991)


Abell 2218 is a very large galaxy cluster, about 2 billion light years from us (yes, that billion with a "b"). It is the dozens of amber-colored blotches throughout this cropped version of the photo (yes, each of those fuzzy little balls is a galaxy, with hundreds of billions of stars); click on the links above the image for uncropped versions in various resolutions. The cluster is so massive that its gravity acts as a lens, making dimmer, more distant galaxies visible to us. My little 14.5" earth-based scope manages to resolve a bit of the lensing effect, but Hubble doesn't have either of those problems, and did better here. For ease of comparison, I have superimposed the Hubble image on top of mine; click here to blink between the two versions. I think it's fair to say that our taxpayers got their money's with that wonderful telescope! But I also think it's pretty cool that a relatively small, amateur, ground-based telescope actually can capture a bit of the lensing effect!

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


Technical Information:

LRGB: 1149:240:240:300 (a bit over 32 hours of exposures); luminance layer consists of blend of 36 thirty-minute images and 23 three-minute images, all using a luminance filter; R channel is comprised of 16 fifteen-minute images taken through a red filter; G consists of 16 fifteen-minute images taken through a green filter, while B is the combination of 15 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, gradient removal, HDR Multiscale Transform for noise reduction) 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 July and August of 2022. Image posted September 19, 2022.

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

Seeing: Generally good

CCD Chip temperature: -25C

Copyright 2022 Mark de Regt

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