I once imaged the Sword of Orion with the Epsilon-200, and the results were OK in my opinion. I intend to redo it on the Epsilon-200 when I get a chance. A while back I also imaged the Sword with my ST80 on the EQ-1 mount. Most of the subs were useless, and I only took 30-second exposures. The results were promising, though.
Last week I had the opportunity to re-image the Sword of Orion with the ST80. I used the Vixen GP mount and the Canon EOS Rebel XS camera. I had to take multiple images at different exposure times because the contrast among different parts of the nebulae is so great. Here is the breakdown of sub-frames:
- 10x1 second (that is, 10 one-second images)
- 10x5 seconds
- 10x10 seconds
- 10x20 seconds
- 23x60 seconds
- 17x120 seconds
I stacked each group of exposures separately, then loaded the six final images as layers in GIMP. I brought out the detail in the brighter parts of the nebulae by using layer masks to cause the shorter-exposure images on lower layers to show through. (If anyone is curious how to do this in GIMP, send me a message and I'll explain in greater detail in another post.)
After the layer masks were complete, I flattened the image and then applied my usual fringe mitigation process. (Again, e-mail me if you're curious how I remove the purple fringes from the stars.)
Here is the final product:
|Sword of Orion, ST80 on Vixen SP, multiple exposures|
There are several separately cataloged objects in the Sword. The group of stars on the left edge of the image is an open cluster that is cataloged as NGC 1981. To the right of that is the Running Man Nebula, which is a combination of diffuse nebulae NGC 1973 and NGC 1975, and open cluster NGC 1977. Near the middle of the image is De Mairan's Nebula, which is cataloged as Messier 43. To the right of that is Messier 42, The Great Orion Nebula. (To me, M43 looks like a bird's head, an M42 looks like the bird's body and wings.) Near the right edge of the image is diffuse nebula NGC 1980, which is illuminated by a 2.75 magnitude class B star called Na'ir al Saif (Arabic for "the Bright One in the Sword").