Saturday, July 6, 2013

Milky Way Around Albireo

Milky Way and Summer Triangle - Canyon of Eagles, July 2013
Canon 60Da, 6 frames at 600sec, f/6.3, ISO-800 Canon EFS 18-55mm IS @ 18mm
Last night, we did some imaging at the Eagle Eye Observatory near Lake Buchanan. Clear skies were predicted but, instead, we dodged clouds all evening. I had planned to image the region around Antares but the southern sky never stayed clear long enough.  Instead, I ended up imaging the milky way centered centered on the well-known double star Albireo (not resolvable in this image).

I mounted the camera on a auto-guided Losmandy GM-8 equatorial mount.  I used  Astro Photography Tool to focus the lens and capture the images and used PHD Guiding to control the mount.

Hover over the image to zoom in on details. You can see the constellation Cygnus in the upper left with the reddish spot of the North American Nebula and the bright star Deneb. Lyra is to the upper right with the brightest star Vega. The constellation Aquila is at the center bottom with the the bright star Altair.  These three stars form the "summer triangle." A bit below the center left is the small diamond-shaped constellation of Delphinus. Finally, if you look closely a bit below of center, you can find the small pattern of stars called the "coat hanger," though it is upside down in this image. This is one of my favorite of these "asterisms."

Single frame at 600sec, f/6.3, ISO-800
With evening temperatures in the 80's, camera noise was heavy. For comparison purposes, this second image shows a single frame prior to stacking and post-processing.  I can hardly make out any detail. Strong color noise is evident in the image as well as in the processed image but it is amazing what a stack of only 6 frames and a bit of post-processing can do to the image quality!

In retrospect, I forgot to turn on position-dithering in the guiding software which would have improved the smoothing out of systematic thermal noise.  Also, I was only able to get 2 dark frames.

I compensated for the strong color noise by selecting everything but the stars and applying a heavy Gaussian blur in the "a" and "b" channels in LAB mode.  I chose a blur radius sufficiently large to blend the color noise without bleed too much of the milky way colors.  Omitting the stars is critical, otherwise they loose color altogether.  I then pushed the overall saturation on back ground and stars.  I also applied and initial correction to the sky gradient with GradientXterminator.

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