NGC 253 (Sculptor Galaxy)
Characteristics:
Magnitude: 7.10
Size: about 25'
Distance: 10 million light years
RA: 0h 47m 36s
Dec: -25 degrees 17' 00"
Description:
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).
Scope: 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).
Post-processing: 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.
Please
note: Graphics on this website
may not be reproduced without author permission.
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