Title says it all. Does anyone have any tips or workflows in PI (or elsewhere) for using DBE/ABE to deal with gradients you know are there, but most the frame contains nebula?
Thanks for any help with this.
Pete
Thanks for any help with this.
Pete
Any tips for dealing with gradients in nebulous dense frames
Engaging
One way is to do this iteratively. You can always start with ABE with function degree=1 and a somewhat large standard deviation for rejection. This will roughly remove the global gradient so you can apply a smaller deviation parameter to better reject nebulas and stars in a subsequent ABE (with higher function degree) or DBE.
If you do the above carefully, you can almost certainly get acceptable results. To get the best and most accurate gradient removal (demanded by mosaic works), you need to take a wider-field image, like 3 to 5 times wider than your main-scope FoV. Run a careful ABE/DBE on that image first. Since it's wide, there should be more nebula-free areas for you to run a robust ABE/DBE. Then you can use that image as a gradient removal reference for your main image. The photometric mosaic script in PI can be used for that purpose and it works quite well.
If you do the above carefully, you can almost certainly get acceptable results. To get the best and most accurate gradient removal (demanded by mosaic works), you need to take a wider-field image, like 3 to 5 times wider than your main-scope FoV. Run a careful ABE/DBE on that image first. Since it's wide, there should be more nebula-free areas for you to run a robust ABE/DBE. Then you can use that image as a gradient removal reference for your main image. The photometric mosaic script in PI can be used for that purpose and it works quite well.
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I did a quick ABE application to my Lum master with the Function degree=1 and and the Deviation set to 6.2 and that gave a decent result. I will continue to reiterate as you outlined above, but I think this will work. Thank you very much.
Your second idea for a much wider field image is something I wondered about. I do have a 275mm fl triplet refractor that I plan to piggyback on the 12"f/4 and that would fit the bill. I could image with both setups at the same time to get the gradient data. Very interesting.
Your second idea for a much wider field image is something I wondered about. I do have a 275mm fl triplet refractor that I plan to piggyback on the 12"f/4 and that would fit the bill. I could image with both setups at the same time to get the gradient data. Very interesting.