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Darkfield Subtraction
hibou from France  [30 posts]
11 years
OK, now I want to go even further :-) and reduce the vertical striations that are due I suppose to the structure of the CCD. I imagine that I can do that with Arithmetic/Math, by subtracting a Darkfield image that I obtain by covering the camera lens and integrating under the same conditions. My darkfield image shows the hot pixels and striations as expected.

I save my darkfield image as a jpg and according to the doc. create a Marker at that point with that name. Then I remove the lens cover and integrate again under the same conditions. I follow that with a Math module in which I subtract my darkfield (which shows up in the pull-down list). But the result is nothing like I hoped - just a rather dark blob of an image. I am misunderstanding something important here. No I did not subtract the average during the integration, which might mess up the darkfield-image subtraction.

What would be good :-) would be to extend the option of "Subtract Average" in the Integration module to allow as an alternative "Subtract Image". This might open a file dialogue listing available jpg files. I realise that the "Math" module provides much more than that - if only I could understand how to use it in this special case :-(
DarkField Subtraction Added
Anonymous
11 years
Alan,

You had the right approach in trying to implement the darkfield subtraction but the issue you had was one of normalization. You need to preserve the pixel range values of the darkfield and the actual image and NOT normalize both of them independently. As there was no easy way to do that we added in a darkfield subtraction capability into the integration module. Have a look at http://www.roborealm.com/help/Integrate.php and see if this makes sense.

We would also like to ask permission to use some of your submitted images as part of the documentation. Let us know if this would be an issue and if you have any additional information such as full name, website, etc., that you would like included alongside those images.

Thanks!
STeven.

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