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NGC 6633 and IC 4756 in Serpens and Ophiuchus





Optics: Sigma 150 mm APO DSLR Lens at f/4; Location: Laguna Mountains, CA;  6 June 2010; Camera: Canon XT 350D (Baader ACF modified)

Exposure: 18 x 6 min  (unfiltered)   ISO 800 , 8 Darks, no Flats 

Processing: Images were captured with DSLR Focus  and saved as RAW file format. Exposures were decoded and dark corrected in IRIS. Exposures were aligned and stacked in IRIS with Sigma Median.  Dark point equalization and rough color balance  were done in IRIS.  Gamma and saturation adjustments were also done in IRIS.  Stretch and crop adjustments were done in Photoshop - Background was set high to show field star density.   Some star repair was performed on edge stars.  Background noise reduction was performed by PixInsight LE  (SGBNR).  Final stretching and touch up was done in PhotoShop.     Final Image size is approximately 3474x2314 - re-sampled and cropped to 2958x1972.

North is up in this image.  This image is guided.  These two clusters are NGC6633 (upper right) and IC 4756 (lower left). They  are set in a dense Milky way star field. IC 4756 is also known as Graff's Cluster. It is about 13,000 light years distant from Earth while is "apparent" neighbor, NGC 6633, is only 1,040 light years distant from Earth. This image is a rather large field of view spanning 8 degrees of the night sky. For perspective, the smaller cluster (NGC 6633) is about the same size as the full Moon.  The Horizontal FOV is about 480 min.

Image Center is approximately - Equatorial 2000: RA: 18h 34m 31s Dec: +0627'44"

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