Quote:
Originally Posted by Paul Haese
Hi Greg,
Martin at the conference said he takes three lots of flats. One at 21,000, one at 26,000 and one at 30,000. Then combines all those to make a master flat. I remember him saying this during his presentation and he has told me this privately too. I suggest you give this a go too. Experimentation of flats will produce the results you are looking for I think.
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Yes I remember that. I was the one who asked him how he did his flats as flats are critical on my CDK and 16803. I think in this case its not a matter of an average of flats (although I intend to try that out) its more a matter of the flats I did take were out of date, or I shifted the camera and did not take fresh flats etc. Hence the difficulty. I have done a lot of experimentation with flats and I think I have it down usually but I must admit I want to try what he suggested out. I find with flats on the CDK I get best results from around 25-30ADU and mean combine and no dark flat subtract merely a bias which is applied during callibration. Plus accurate darks. That is with the Proline 16803.
I think you will find the same on your RC12. Its the long focal length where these donuts show up way more than on shorter focal lengths. The best thing obviously is to keep everything regularly cleaned. These donuts are on the sensor CCD chamber window not so much the filters.
I thought it was a clever idea to average several as you definitely do get different results with different ADU.
Quote:
Originally Posted by alpal
Hi Greg - it's easy.
In Photoshop you make an inverted layer mask.
It ends up like this:
You then apply it to the image & get the result.
With a bit more fiddling around I could have got it perfect.
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Hey that's good. How did you make that inverted mask?
I used a similar background sampling using the ellipse lasso tool, move it over the dust area and blend it in with a reveal all mask to let the original stars through.
I've posted the result of doing that and whilst there may be some minor residual dust it only shows up on huge curves boost now. See what you think - same links.
Thanks for the suggestions.
Greg.