star trails help

Started Nov 17, 2011 | Discussions thread
gribley
Junior MemberPosts: 30
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Re: star trails help
In reply to tadj1, Nov 20, 2011

Nice job, tadj1! Looks good, and I can clearly recognize Orion and the Hyades.

The non-moving points are obviously not stars. I assume they are some sort of camera noise, although I'm surprised they're that bright. But if you have hot pixels, they will get added together every time. Do those appear in each of your individual images?

I assume you have turned off the dark frame subtraction. (If you had left it on, there would be 60-sec gaps in your star trails.) The point of the dark frame subtraction is to remove all the noise and flaws from the sensor itself, so it should take care of the hot pixels. (The DFS process takes a picture, then a second one with the shutter closed, and subtracts the second from the first -- so a hot pixel or noise in the sensor should get subtracted out.)

Why not try a single long exposure, 5 or maybe 10 min, with dark frame subtraction on, and see if you still get those points?

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