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Old 05-05-2011, 08:12 AM
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avandonk
avandonk

avandonk is offline
 
Join Date: Aug 2005
Location: Melbourne
Posts: 4,786
Your biggest enemies for doing mosaics of wide fields is vignetting and sky gradients.

Very good flat correction is critical. Even then the corners and edges are very difficult to merge seamlessly.

I have gone to extraordinary lengths to limit any stray light with an extended lens hood and front aperture. I use a 82mm Hutech LP filter mounted in front of the lens.

For a two panel mosaic I use Registar to register the two frames. The combination of the two will quickly tell you where there is a colour brightness missmatch at their overlap.

It is important to process both panels the same way.

Trick one.

Use the full frame of both panels to produce a registered version of panel two to the reference panel one.

You can now trim/crop both with photoshop to have a far thinner overlap region where there is minimal vignetting etc. You trim both panels to make the overlap an even width. Since the second panel is already registered no distortion will occur due to a small area of overlap. Make sure there is no black region in the overlap from panel two.

Now run RegiStar again and calibrate the second panel for colour and brightness. Average combine the reference (panel one) with the calibrated panel two.

Inspect for a good match. It should be far better than using the complete panels.

When you have got this correct I will explain how I go about three, four and more panels.

Feel free to ask questions if I am not clear.

Bert
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