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Pinwheel Galaxy - M101



Scope: Celestron 9.25 Edge HD 235 mm at f/7, Location: DAA Observatory, Shelter Valley, CA,  22 and 24 March 2020,  Camera: ST8300M (Baader LRGB filters)

Exposure: Exposure: 42 x 8 min  (2x2 bin) exposure with UV/IR block filter,  16 x 5 min (2x2 bin) each RGB exposures.

Processing: Data Collection -  Sequence Generator Pro (as FITs).  Subframe calibration - Pixinsight. Subframe integration (Average combine -  Winsorized Sigma Clipping) - PixInsight.  Non-linear stretching, normalization and gradient removal - PixInsight. Curves, Levels, RGB combine, Luminance layering - PixInsight.  Final finishing  - Photoshop.  RGB calibration - eXcalibrator. Annotation - PixInsight, Aladin (Simbad and NED), and PhotoShop. This image is an RGB combine with Luminance layering. Images processed at 3352 x 2532 resolution. Final Image size is approximately  2800x2100.

North is up in this image.  This image is dominated by M101 (also known as Arp 26 and NGC 5457). In Arp's Peculiar Galaxies catalog, it is classified as "spiral galaxy with one heavy arm". Arp's observing notes describe the "one heavy arm" as having a "bright knot"  This bright knot is likely NGC 5462 - A HII region. There are seven other such regions (NGC 5447, 49, 50, 51, 53, 55, 61). An eighth, NGC 5471, is either a HII region or a Wolf-Rayet companion galaxy. NGC 5477 is the galaxy on the left it is a member of the M101 galaxy group. There are 21 members according to the Simbad database - most of which are not in this image's field of view. These objects and some of the brighter stars and background galaxies are identified in the annotated image. This image replaces an earlier image that can be seen in the Archives here. Horizontal FOV is approximately 38 arc minutes. Full size image scale is 0.81 arcsec/pix.

Image center is approximately - Equatorial 2000: RA: 14h 03m 42s Dec: +5423'27"


All images and content remain the property of Jim Thommes - copyright 2003 - 2020

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