Stretching PNs with very high dynamic range

[astrovienna]

Could anyone walk through how to process PN data like this:

https://dl.dropboxusercontent.com/u/58468743/M57HaOIII.zip

to get both the core and the halo?  I can't seem to process this without an abrupt, ugly jump between core and halo.  I know I could take exposures of shorter duration for the core (and use one of the HDR tools to merge them), but that seems unnecessary here, since the core isn't blown out and the halo is nicely visible with some stretching.

Kevin

[sreilly]

Try using Masked Stretch at 0.125 w/o a preview and then HDRW using as set in the screen capture but first with three (3) layers and then at five (5) as below:

[vicent_peris]

Here it is. Two notes:

- The color image is created with ChannelCombination. H-alpha goes to R, OIII to G and B.

- "Lightness_mask" is the L component extracted from the color image after the second histogram transformation.


V.

[astrovienna]

Thanks, Vincent and Steve.  That was really helpful.  Both techniques seemed to work well.  In the end I followed Vincent's strategy and used AutoHisto, a tool I've never used before, instead of MaskedStretch, then applied HDRMulti.  Final results are here, one for the core only and one with the halo as well:

http://www.pbase.com/skybox/image/164511421

http://www.pbase.com/skybox/image/164511382


Kevin