M94

M94: This spiral galaxy is in the constellation Canes Venatici. The very symmetric disk is not quite face-on, and shows distinct rings of stars as part of its spiral structure. The inner ring is bluish in color because of active star formation and young, hot stars. There is also a fainter, outer ring of stars not shown in this image. The galaxy is approximately 16 Mly distant and has been the subject of several recent studies. See http://en.wikipedia.org/wiki/Messier_94 for more information.

Messier: 94
NGC: 4736
Right Ascension: 12h 51m
Declination: 41° 7'
Apparent Magnitude: 8.99

Date: May 2014
Equipment:
Telescope: Meade 16" Schmidt Cassegrain with f6.3 reducer
Camera: SBIG ST-10XE
Guiding: Meade 5" refractor; Starshoot Autoguider; PHD

Exposure:
L: 17x3 minute subframes binned 1x1.
Color frames were taken with photometric (RVB), rather than photographic (RGB) filters.
R: 9x5 minute subframes binned 2x2.
V: 10x5 minute subframes binned 2x2.
B: 10x5 minute subframes binned 2x2.

Processing Notes: Data acquisition with CCDSoft. Reduction, and alignment, data selection and combination with CCDStack. RVB was combined in CCDStack with a ratio of ~1:1.7:5, and using a background white balance. L and RVB images were stretched and tweaked separately in Photoshop and combined with layers. Significant smoothing and increase in color saturation on RVB image. The luminance layer received slight sharpening via unsharp mask on the brighter areas, and Gaussian blur on the dimmer areas. Contrast enhancement was achieved by applying a highpass filter in a duplicate luminance layer set as an overlay.
Scale: .53"/pixel

Links to images of this object on other sites:
http://apod.nasa.gov/apod/ap100114.html
http://www.spiegelteam.de/M94.htm

Additional Comments: Because the core of M94 is so bright, the luminance frames were shorter (only 3 minutes) than many of the galaxy images taken at this observatory. The fainter outer ring of stars does show up if the background is stretched beyond what is aesthetically pleasing, and a set of longer exposures should easily bring out the details of the "extra" ring, as well as many more distant background galaxies.

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