Iris nebula and red giant in Cepheus
The Iris nebula (NGC 7023/Caldwell 4) is a bright reflection nebula in the constellation Cepheus. Its magnitude is near 7, apparent size 18×18 arc minutes, real size 6 light years across and distance of 1,300 light years. In its center lies a massive hot young star in its formative years. The dominant color blue is characteristic of dust grains reflecting starlight. Mostly obscured by dust is the loose open cluster Collinder 427.
Looking down on this beautiful nebula at the upper right is T Cephei, a massive pulsating red hypergiant. It is a Mira variable star, fluctuating in magnitude between 5.2-11.3 over a period of 388 days. At the time of image it was approximately 7.36. Its radius is 540 times that of our sun.
Acquisition details: Late Oct 2011 MASP using tv85/em-11/canon 40d unmodified/tv 0.8 reducer/IDAS LPS. 4 minute unguided exposures, 26 light/25 dark/10 flat. (Nearly no other images from MASP had flats). ISO 800. 1.6 camera crop factor for an end result of 768mm focal length. F7 became F5.6 with the reducer/flattener. Cepheus was entering down into a light dome in the north so I put on the IDAS filter but most other images from this series were sans filters. Acquired with Maxim DL, RAW Monochrome.
Processing details: Color convert in Maxim. Stacked with DeepSkyStacker. Levels and Curves in Photoshop CS4. Gradient removal with GradientXTerminator. Noise reduction with NoiseNinja. Often a slight crop is performed to obtain a more pleasing composition. Resized from 3908 x 2602 down 75% and converted to jpg to get a reasonable image size of ~ .5 mb or so from a start of around 60mb.