| The Colors of Saturn in 2023 by Christophe.P |
Hi all, here are more UV data and some indices, where dividing one band with another brings interesting stuff. 1) Since last year I'm using a shorter UV-pass filter than the Chroma Bessel U, the Asahi 340. Used with the T620 AstroQueyras without barlow at an altitude of 3000 meters, the filter succesfully detected the increase of albedo of the planet before 350 nm. Actually on that band, the southern hemisphere around 40°S is brighter than the rings ! My photometry of that filter failed (the only one) so I have evaluated the expected value by looking at the Saturn spectrum inside the passband of the filter. While in the U band the albedo is around 20%, through the UV340 it raises to 0,22. The Chroma U used at the AstroQueyras Observatory looks to produce more contrast between the EZ and the rest of the globe, maybe because at that good site, shorter wavelengths are caught, despite the filter and the camera being exactly the same. Then, in the scientific litterature (Karkoschka, Sanchez-Lavega...) we find 2 indices: 2) Dividing blue by red produces a color index, where we measure how red or how blue are the Saturn latitudes. The index correctly shows that the southern winter hemisphere was noticeably bluer over the past years, and it also correctly shows that it has reddened in 2023 in comparison with 2022 (from blue to green). Let's see how it turns in 2024, the winter hemisphere looks bluer to me than last year so far... 3) Dividing CH4 by UV. This should be done with a UVB filter (in the litterature we find data from the F275M HST filter), but of course it is impossible from the ground. To the contrary of Jupiter however, the aspect of Saturn in UVA is much closer to that of UVB, so I tried it anyways. This index measures how high/opaque are the clouds, and without any surprise the Equatorial Zone is occupied by noticeably higher and thicker clouds than elsewhere. Ricardo again, I don't know if it is acceptable on Saturn to measure this index through UVA ? On the next time I will send my data about the rings
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