Spiral Galaxy in Ursa Major

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M101 is one of the more striking spiral galaxies (like our galaxy, the Milky Way) in the northern sky; It is a grand design spiral galaxy, with about one trillion stars (twice as many as our Milky Way is thought to have). It has a diameter of approximately 170,000 light years, making it a relatively large galaxy (our Milky Way now is thought to be a bit larger than that, perhaps 200,000 light years across). The field is about the angular size of a full moon.

Its relatively close distance of about 22 million light years allows it to be studied in some detail. It is located in Ursa Major (of which the Big Dipper is a part), near the tip of the handle of the Big Dipper. Recent evidence indicates that a close gravitational interaction with a neighboring galaxy created waves of high mass and condensed gas which continue to circle the galaxy. These waves compress existing gas and cause star formation. One result is that M101 has several extremely bright star-forming regions (called HII regions) spread across its spiral arms (which appear as pinkish blobs in the picture). M101 is so large that its immense gravity distorts smaller nearby galaxies.


Technical Information:

LRGB: 375:150:150:150; L consisted of twenty-five 15-minute unbinned images; R, G and B consisted of ten 15-minute unbinned images each.

Equipment: 16" RCOS at about f/9, and an SBIG STL-11000M with internal filter wheel (Astrodon filter set), on a Bisque Paramount ME German Equatorial Mount.

Image Acquisition/Camera Control: CCDSoft v5, controlled with CCDAutoPilot3, working in concert with TheSky v6.

Processing: All images calibrated (darks and dawn flats), debloomed, aligned, sigma reject performed, and combined in CCDStack. Luminance layer deconvolved in CCDStack. Color combine in Photoshop. Finish work (curves and levels, increasing saturation, smart sharpen and Local Contrast Enhancement on luminance layer) was done in Photoshop CS2.

Location: Data acquired remotely from the Tejas Observatory, located on the grounds of New Mexico Skies, near Mayhill, NM (elevation 7300 feet).

Date: Luminance images taken on the nights of May 12, 23 and 24, 2007. Color images taken during the nights of May 11, 12 and 23, 2007.

Pixel scale: .505 arcseconds per pixel.

CCD Chip temperature: -25C

Seeing: Very poor.

Transparency: Good.

Moon Phase: Varied.

Copyright 2007 Mark de Regt

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