M57 (and IC1296): Stars with mass similar to that of our Sun throw off their outer gasses after fusion has stopped in their core. One of the most famous, and easily found, of these "planetary nebulae" is the Ring Nebula, M57. It is believed that the ring part of the nebula is actually shaped like a torus (doughnut), and the center is shaped like an American football, looked at from one end; larger scopes than mine show the outer halo to have a very complex structure. The bluish star at the center of the nebula is the old core of the star, now evolving into a white dwarf. Nebulae of this type are called "planetary nebulae," because in older smaller scopes, they looked like small, blurry planets. It is about 2000 light years from Earth, visually in the constellation Lyra. At that distance, the halo in my photo has a diameter of a bit less than 2 light years. IC1296, a magnitude 15 barred-spiral galaxy located about 240 million light years from us (or 120,000 times as far from us as M57), can be seen to the lower right of the nebula.

As with many planetary nebulae, this one is rich in both ionized hydrogen (the reddish parts) and ionized oxygen (the bluish parts).

M57 is an easy visual object for even a modest telescope (or binoculars), and looks like a slighlty-oblong smoke ring (no color shows through any telescope through which I have observed M57). It is a challenge to photograph effectively, since the ring structure is much, much brighter than the halo around the bright part of the nebula, making it difficult to show the halo without having the ring overexposed.

I have imaged this target previously; most recently 18 years before I took this version, with fairly elemental equipment (at least by comparison), and from my own yard. I have always liked that version, but I wanted to see what I could capture of the very faint halo; if you want to compare the versions, click here.

Technical Information:

HaOIIILRGB: 570:540:555:210:180:240 (L, R and G individual images were all 15-minute exposures; B images were 20 minutes each, and Ha and OIII were 30-minute individual exposures). All images were unbinned. The pink regions are Ha emissions, and taking exposures through an Ha filter helps bring out that color; the bluish regions are characteristic of OIII emissions, and taking images through an OIII filter helps bring out that color. The outer halo is a mix of Ha and OIII emissions (and probably some other emissions).

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 monochrome camera with internal filter wheel (SBIG filter set), guided by an SBIG AO-X, 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 Professional Edition.

Processing: All images calibrated (darks, bias and sky flats), aligned, combined and cropped in Pixinsight. RGB Color combine in Pixinsight. Some finish work (background neutralization, color calibration, HDR Mulitscale Transform and Multiscale Linear Transform of luminance data, and noise reduction) done in Pixinsight; LRGB combination and some further finish work was done in Photoshop CC.

Location: Data acquired remotely with my equipment hosted by Sierra Remote Observatories, Auberry, California, USA.

Date: Images taken on many nights in July and August, 2021. Image posted September 22, 2021.

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

Seeing: Generally very good, with individual calibrated luminance frames varying from 1.6 to 2.4 arcsecond FWHM.

CCD Chip temperature: -25C

Copyright 2021 Mark de Regt

Hit Counter