M57 (The Ring Nebula)

All Images Copyright Steve Cannistra

Please click here for the full scale version (100%).
Please click here for the inverted grayscale image (100%).

Magnitude:  Approximately 8.8
FOV: Approximately 20' x 30'
Distance: 2,300 light years
RA (J2000): 18h 53m 35s
Dec (J2000): 33 degrees 01' 36"
Position Angle (Pinpoint):  plus 12 degrees

Messier 57 is a planetary nebula, which represents the end stage of stars about the same size as our Sun (in contrast, stars much larger than our Sun typically undergo a supernova explosion).   Such stars experience a phase of continued helium burning on their surface, long after the fuel in their core has been exhausted.  The outer layer is shed into space, igniting surrounding elements such as hydrogen through excitation by the solar wind and heat.  The term "planetary" nebula is a misnomer and was coined by Herschel, based upon its superficial visual resemblance to his recently discovered planet, Uranus.  This is an LRGB composite in which Ha signal was added to the red channel in order to reveal the faint outer shell.  I did not have much time to acquire more luminance signal, but the signal to noise was quite good despite only 90 minutes of unblocked luminance (since the object is fairly bright).  A nice description of M57 may be found on Rob Gendler's site.

Photographic Details:
Date:  May 26, 2008 (Ha); May 29, 2008 (LRGB)
Scope:  Vixen VC200L at f9 (FL = 1800 mm) on the Takahashi NJP Mount.
Autoguider:  SBIG ST-402 with Sky90 at f4.5.
Camera:  Apogee U32 -20C.

Astronomik Clear (unblocked), Ha (6nm), R, G, B filters.
Exposures:  Luminance: 18 x 5' = 90' (unbinned); Ha: 3 x 30' = 90' (unbinned); R: 3 x 10' = 30' (binned 2x2); G: 3 x 10' = 30' (binned 2x2); B: 3 x 15' = 45' (binned 2x2).  Total exposure 4.8 hours.
Conditions:  I could only salvage 90 minutes of Ha exposure on 5/26/08 due to clouds.  May 29 was a near perfect night with seeing in the range of 2.8" (good for my site).
Post-processing:  Calibrated, aligned, and Sigma Clip combined in Maxim.  DDP in ImagesPlus (IP).  Deconvolution in AIP4WIN.  Further processing in Photoshop CS (16 bit format).
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