Night sky panorama experiments

Started Sep 22, 2011 | Discussions thread
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masoncl
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Night sky panorama experiments
Sep 22, 2011

Hi everyone,

I've been trying to get some long exposure shots of the night sky and playing with different tools to stitch them together. To get the stars, I need about f1.7, iso6400, 10 seconds. But this has a ton of noise, so I took a stack at lower isos then blended them together with hugin. The blending really cuts down on the noise and then you can push the exposure up with better results.

I used iso400 and iso800 because the noise makes it very hard for hugin to align the star images. Darker shots are easier to align. These were all shot with my g3 and the 20mm lens. Wider lens allow longer shots, but the 14-45mm would have ended up with less light overall at the longest exposure without star trails.

The second challenge is lining up the ground with the stack. The stars move pretty quickly, so you can't take a 10 second exposure from high in the sky and line it up with a 10 second exposure that includes the ground. I tried two different ways of merging the whole thing together.

First I have iso800 stacks (4 images for each part of the pano), where I tried to line up the ground by hand. It mostly works, but the haze is because I couldn't quite get the sky to blend properly. There are also a few spots where only one image from the stack contributed to the pano, and these have a ton of noise.

Second is an iso400 stack (10 images for each part of the pano) where I lined up the ground with hugin's masking feature. Basically I masked out the ground from all but one of the images in the stack, and had hugin use only the stars for alignment. Then I reversed the mask and made a second image with just the ground stacked (to reduce noise) and blended them together.

The iso400 shot has a ton less noise, but that's because I had more images in the stack. I think the iso800 photos look better overall, I'll try 800 and 1600 again the next time I'm out.

Just for comparison, here is one of the iso400 images before stacking. It comes from the lower left corner of the sky in the second photo.

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