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M81 etc

Guest Ely Ellis

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Guest Ely Ellis

Before going to work, I had my Canon 450D (Unmodified) on the scope and managed to take this image of M81.

There appears to be some light pollution at the bottom half of the image that I just can't get rid of.

Took about 90 subs and 90 darks at ISO 800, 45 seconds. (I think)

Any comments please.


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Nice shooting there Martin.

Why do you use so many darks.

I have been advised by a proper camera techie ( he designs camera chips ) that you should use about a 5 to 1 ratio of lights to darks up to a max of 21 darks.

Anything over the 21 the stacking program will start to interpret consistent points in the darks as stars an then add these points to the final image.

Because of the maths involved with the way the chips work the next number after 21 to have an equal effect on the final image is 4 times the number. IE 22 = 88 ,, 23 = 92 ect ect.

He also recommends that you use an odd number as well.

Personally I don't have a clue about what he was explaining to me as it was way over my head but I have used his advice ever since and it works a treat.

It also saves you a lot of time taking the darks.

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Guest Ely Ellis

Thanks everyone for you comments.

Graham, that is a handy tip to know.

In some of the tutorials I have watched, they do state 21 or above Darks, so maybe it should have been just 21.

I will give it a go and see what happens. If it turns out better, then I will re-post.



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