I have been experimenting with the GHT and it appears to be a very powerful tool but there is a problem when the image is translated into formats other than FITS. Here is a screenshot side by side of how an example image looks in Siril vs. when saved as tif, png or jpg:
It appears that the MIPS-LO parameter may be the culprit. It is around 0.27 and this is put into the FITS header as “MIPS-FLO” with the comment “lower visualization cutoff”. Maybe this isn’t taken into account when translating the image into other formats. If, on the other hand, this is just user error, I would like to understand what I’m doing wrong.
Also, the new symmetry point selection feature doesn’t work in 16 bit mode, and always sets the symmetry point to 1 regardless of the selection area.
It is because the cursors are not to 0 and max. See also Why are exported images so dark? in the FAQ. So yes, it’s because of MIPS-LO to some extent, but mostly because the display settings are wrong.
OK. The problem is that it is the tool itself that is setting the MIPS-LO as I adjust the stretch factor and intensity. If I then manually reduce MIPS-LO to zero, I don’t seem to be able to make adjustments in the GHT tool to get back to the same appearance. It does appear that I can manipulate the histogram afterwards and maybe get back to the same appearance. I also notice that the GHT tool does a great job of bringing out star colors but for some reason turns the nebula to gray (instead of mostly red if I do a normal histogram stretch). Maybe I need to separate out the RGB channels and apply the tool independently to each channel, but I would think that will destroy the color balance from photometric color balance.
