Wednesday, September 12, 2012

M27 -- The Dumbell Nebula

I captured this image last night with a Nikon D40 DSLR, running at 3200 ISO.  Only about 4 of the captured images were actually stackable, so this image represents around 3.5 minutes of actual imaging time. The resulting image was, of course, very noisy.  Noise reduction has softened the image somewhat.

SLR imaging is a cheap way to get into deep sky captures, but it is far from perfect.  The D40 does not have mirror lock up, so I had to cover the scope aperture when I began the exposure, otherwise the vibration caused by the movement of the mirror in the camera causes distortions in the star images (they usually look like little chevrons).  It takes about 5 seconds for the scope to damp down the vibrations after the shutter has been opened.  I stacked the images with DeepSkyStacker, which does a much better job with DSO images than Astrostack.  Histogram stretching was performed in Astrostack, with final processing in Windows.

If you decide to try imaging with a DSLR, I would also remove the strap.  When I started imaging, I noticed that stars were showing very anomalous and varied shapes.  At first, I blamed tracking, but ti turned out to be the breeze moving the camera strap and causing vibrations!