NGC 253 (Sculptor Galaxy)

NGC 7331
All Images Copyright Steve Cannistra

Please click here or on image for a higher color resolution view.

Magnitude:  7.10
Size: about 25'
Distance: 10 million light years
RA: 0h 47m 36s
Dec: -25 degrees 17' 00"

NGC 253 is a large, dusty spiral galaxy located in the constellation Sculptor.  It was discovered in 1783 by Caroline Herschel, sister of William Herschel, and is the nearest galaxy to our Local Group.   More information about NGC 253 may be found here.

Photographic Details:

Date:  October 21, 2004 (luminance); October 23, 2004 (RGB).
Takahashi Epsilon 250mm aperture, F/3.8 astrograph (850mm focal length) mounted on a Paramount GT1100ME mount, located in an observatory near Mahill, New Mexico.  I accomplished scope/autoguider set up and image acquisition by remote control over the internet from my home in Needham, MA.  A zip file of the raw subexposures was downloaded after completion of the session, ready for processing.  Scope time was rented through Rent-A-Scope.
Camera and autoguider: 
ST-8XE CCD camera (NABG).
Filter:  Custom Scientific Clear, R, G, B filter set.
Exposures:  Luminance: 85' total (17 x 5'), unbinned.  RGB:  4 x 2' each for R and G; 5 x 2' for B, binned 2 x 2.
Conditions:  Clear skies in New Mexico.  Cloudy in Massachusetts.  NGC 253 was low in the southwest while obtaining RGB data (I needed to wait for the moon to set).
Blooms were removed using Ron Wodaski's DeBloomer plug-in for Maxim. 
All images were then dark, bias, and flat frame calibrated.  Alignment done in MaximDL.  Sigma combined using RC Sigma Reject plug-in for Maxim.  DDP and gradient correction performed in ImagesPlus (IP).  Subsequent processing including levels and curves adjustments in Photoshop CS (16 bit format).  Final sharpening with Lucy-Richardson deconvolution in ImagesPlus (PSF 5 x 5; 4 iterations).  I could not obtain deep color data in view of the galaxy's location low in the southwestern sky after moonset (which limited RGB exposure time and also attentuated the color signal due to atmospheric extinction).  Thus, the HII regions contained within this galaxy are poorly seen in my image.
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