wide field: Orion Descending

This is a first light image with my new Canon 14mm lens, using the modified Canon 50D, captured at the blue/grey LP boundary south of Foymount. As dithering is impossible with a wide angle lens, I used the native Canon long exposure noise reduction feature (generates a dark for every capture & automatically subtracts it). Thirteen raw camera files were converted to 16 bit tiffs with Photoshop and stacked 'by hand' in Photoshop.

Prominent objects in the image are labeled (mouseover), and the Milky Way slants diagonally across it. Captures began when Orion was about an hour past transit, sinking in the west. The orange glow in the bottom right corner is light pollution reflected from distant clouds over Toronto: at the end of captures, that part of the image was only 10 degrees above the horizon (the long dimension of the image spans 76 degrees). The image has been distortion-corrected, which results in the white corner gaps (see my star trails image from the same night for further details). The image is uncropped.

I am impressed by the quality of this image. Even before distortion correction, the coma and chromatic aberration in the corners were not much worse than that from a low-end apochromatic refractor, and the correction improves that. The image is very well focussed: in the full-resolution image one can make out some detail in M42 and the Flame Nebula, and the Horsehead Nebula can be seen, although its shape is obscured. This lens will perform extremely well under darker skies, where longer exposures will be feasible, and has an enormous field of view for capturing meteor showers.

I experienced again that I am sometimes too fussy with polar alignment. After setting up, I discovered I had not pointed close enough to north and I had to manhandle my tripod and mount to get Polaris in azimuth range. That obliterated my leveling, which I recovered as best I could on the slush-covered muddy ground, and I just placed Polaris in the right quadrant of the polarscope and crossed my fingers. From the first frame to the last, there was not one pixel of drift in my images!

March 8, 2013; south of Foymount, Ontario; 14mm lens on Canon 50D; 13x120s with native noise reduction (approximately 1 hour elapsed time); ISO 800 and f/5.6; no filters; temperature was 0 to -5 C; seeing /transparency average.

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