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Gradient and M81


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Hello,

I've only just started taking deep sky images, in the last week or so. With a 350d at prime focus of a 200p.

I thought I would go for M81 unguided (which I know is not ideal) I am limited to 1 minute exposures for the time being.

Anyway my first night, I got data with 30 second subs and there was a gradient to the left.

I tried again another night with 1 minute subs, got 38 of them at iso 1600. Then flats and darks.

Exactly the same gradient toward the left and bottom left of the image is there again. Is this amp glow or something to be worried about?

I know I need more data than 38 minutes for a good picture of a galaxy my question is just, if with flats and darks I keep getting the same gradient to the left, surely the gradient will get even worse with more subs?

My garden seems pretty dark and the light pollution is minimal especially at M81's height.

This is 38 x 1 minute subs fresh from deep sky stacker after fiddling with the settings in deep sky stacker a little (saturation, midpoint etc).

Is this amount of detail about right (whats to be expected) from the integration time?

Sorry for the silly questions, as I say I'm very new to deep sky imaging.

post-26081-0-38602100-1367251446_thumb.j

Thanks,

Dan

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That is a great improvement! Was that Gradient Xterminator?

Yeh, I really wanna find out the cause of the gradient!!

Tbh I want to completely rule out light pollution. I thought perhaps the eyepiece as it was uncovered although I searched and people say theres no light leak whatsoever.

Dan

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Ok wow.

After reading numerous posts on the internet saying when the mirrors up there cant be much light leak I came to the conclusion that this wasnt the cause.

However, I just took a dark frame with the eyepiece uncovered then a dark frame with a not very bright torch around a foot away shining onto the viewfinder and WOW. Masses of light leak.

The second one looked more like a flat frame than a dark! Lesson learnt...

Dan

Edit: Thinking about the position of the telescope and the camera for M81, the rising moon will have been directly illuminating the viewfinder. Not sure how a dim torch compares but this is surely the cause!

Edited by long_arms
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theres a fair bit of detail just for 38min you done well. it would probably help if you cover the mirror on the back on the scope at least this way you will elimate one source of light leak, but i dont think this is what caused the gradient maybe the moon. can you post a single sub

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