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August 3, 2011

There are currently a lot of bright emission nebulae in the northern sky well placed for shooting.  Even better, I haven’t shot too many of these.  This is another one I haven’t seen imaged too often.  Sh2-132 is one of the 312 bright emission nebulae catalogued by Stewart Sharpless.  All of the Sharpless nebulae glow from the light of ionized hydrogen, which has a characteristic red colour.  Some of these objects have been listed in other catalogues, but I don’t think Sh2-132 has another catalogue designation.  Sh2-132 is about 1200 light years away. It shows dark patches, which are due to soot blocking out the light of the nebula.  This image brings out the core of the nebula nicely, but there is a huge patch of billowing, faint nebulosity that I’ll capture in a future shot with a shorter focal length ‘scope. I have a new scope on order that should do the trick — I have heard it may arrive around August 20th.

Twenty-minute unbinned frames were acquired as follows:  R, G and B and Ha 100m each, and Ha 120m.   Total acquisition time was 7hr, acquired over 2 nights.  QSI583wsg camera, Astrodon 5nm Ha filter, Astrodon LRGB Gen-2 filters, and an 8″ f/8 RC on a MI-250 mount, from my SkyShed in Guelph.    No moon, no cloud, excellent transparency and average seeing.  MaximDL was used for acquisition, guiding, calibration, alignment and stacking. A QHY5 camera was used to guide through the QSI’s guide port.

All processing was done in PixInsight except the final step.   Dynamic Background Extraction was applied to the Ha and RGB images.  Then the red channel was extracted and modified by blending with the Ha data using Vicent Perris’ formula in PixelMath.  The new red channel was combined with the original green and blue channels to make an HaRGB image.  This was processed with Colour Balance, histogram stretch, masked sharpening, curves and noise reduction (masked, 2 different noise scales).   The HaRGB image was saved as a 16-bit tif file. Photoshop was used for slight and selective sharpening with a high-pass filter layer blended using the soft light blend mode, heavily masked. Image scale for this telescope/camera combination is 0.68 arcsec/pixel.

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