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Posted by: Antdoghalo Apr 15 2022, 01:19 AM

I am trying to figure out the color of Ceres and in the PDS, I have come upon the fact that Dawn used 8 color filters but I don't know which ones were RGB and what the other 5 were. Does anyone have leads on this info?

Posted by: mcaplinger Apr 15 2022, 01:36 AM

QUOTE (Antdoghalo @ Apr 14 2022, 05:19 PM)

Posted by: Antdoghalo Apr 15 2022, 12:19 PM

For an RGB composite image, would I use the F3 or the F7 filter for the red?

Posted by: fredk Apr 15 2022, 02:18 PM

749nm is pretty long for red - our cones don't respond much out there.

Presumably you're going to be adjusting colours by eye anyway, and not doing a proper transformation from raw colour space to sRGB or whatever, so it probably doesn't matter too much.

Posted by: djellison Apr 15 2022, 02:19 PM

Depends on your intentions…..For a crude, approximate ‘true color’ (whatever that means) image - use F1,2,3.

Posted by: Antdoghalo Apr 15 2022, 07:53 PM

When I try this in Gimp, It's either really blue or its somewhat green, not pinkish grey with bluish spots.

Posted by: djellison Apr 15 2022, 10:28 PM

What is your pipeline before throwing images in to gimp?

Are you using radiometric calibration?

Posted by: Antdoghalo Apr 16 2022, 12:55 AM

I just throw these in with the indicated channels: https://sbnarchive.psi.edu/pds3/dawn/fc/DWNCHFFC2_2/EXTRAS/
Is there a process I need to edit them with or do they need to be the converted img files?

Posted by: djellison Apr 16 2022, 03:42 AM

OK - that's just projected maps in different channels. There's no radiometric calibration there as such - you're not going to get the colors you're expecting.

Posted by: mcaplinger Apr 16 2022, 04:59 PM

Ceres is basically gray. If you're just messing around for fun, you can simply adjust the color channel brightness until the overall color is gray, and then change the contrast to see if you can bring up subtle color differences.

To really do science, you have to use and understand the radiometrically-calibrated image products.

Or you could just read https://www.researchgate.net/publication/313016247_Resolved_Spectrophotometric_Properties_of_the_Ceres_Surface_from_Dawn_Framing_Camera_Images