Monday, March 09, 2009

42 Orionis nebula (NGC 1977)

Click to enlarge. A total of 53 images, each 15 seconds each, totaling 13:25 minutes. Taken on December 29th, 2008.

42 Orionis is a bright B1 star in Orion's sword, just to the north of the spectacular Orion Nebula (M42 & M43). It is always overshadowed by its neighbor and many miss the NGC 1977 nebula entirely because the Orion Nebula is almost always glowing in the field of view and very distracting. NGC 1973 is the nebula surrounding the star in the upper right of the frame. 42 Orionis itself is the bright star just to the right of center. The bright star to the left of center is 45 Orionis, an unrelated foreground (370 ly away) star. Unwritten is that this nebula is part of the same giant Orion Molecular Cloud complex that the Orion Nebula is part of.

As always, I am never happy with processing. On this one, there were a significant number of sub-images that were trailed. Normally I align all the subframes and then add the subs together. Since adding will send the pixel values all to 32767 (I use Iris, which is limited to 16 bits), in most cases I utilize either a median combine (which will get rid of the trails) or use "add_norm", which normalizes the final result to fit in 16 bit space. However in this one, I first multiplied all the values in all the images by 0.02, then added them all up, then I subtracted the images I knew were trailed. Some modified equalization and a touch of gamma, and all done. Until I am unsatisfied again.

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