Sunday, October 21, 2012

Astrophotography with Sigma 100-300mm f4 and D800

Last night was the first clear sky in about a month. That's quite long time to wait, si I didn't want to waste this opportunity and went straight outside with Astrotrac. The first target was Andromeda's galaxy or M31: big, bright and overall easy target to photograph even with heavy light pollution.

I'm continuously amazed by the D800 and its sensor and this time was no exception. This time I mounted Sigma's 100-300mm f4 telezoom to D800. Astrophotography is the most demanding subject lens-wise: any chromatic aberration, coma, halation, spherical aberration, focus shift will ruin the pictures very fast. Luckily, the Sigma had no problems image quality wise.

Here's nine image long stack of M31 (250mm f4, ISO 800 and 2 minutes per exposure) stacked together in Hugin and Enfuse:

Messier 31

And here's 100% crop of the galaxy's center region, the dust clouds in the spirals are clearly visible:

M31 (crop)

When stacking images in Enfuse, one must remember to set the sigma parameter to maximum value (1) and weight only exposure. This way, the images get averaged together very cleanly. One good thing about Hugin is that is quite fast aligning the images, I'm processing the same images in DeepSkyStacker and it's been going for an hour and a half no and haven't yet produced anything. Of course, DSS works straight with raw files whereas Hugin uses TIFFs, but even factoring the raw development time with Raw Therapee, Hugin is still faster - by a fair margin.

Lyyran rengassumu (M57)

Above is a test shot from the Lyra's M57, a small planetary nebula. That was the last image before the clouds rolled in.

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