Talk:Color index

Sample Table

It's a minor thing, but since the filters, in order, are UBVRI it seems like the table columns should be ordered U-B, B-V, V-R, and R-I instead of the current ordering which is B-V, U-B, V-R, and R-I. I want to change it, but there may be a convention I'm unaware of that lists them in this order. So I'll leave it for now pending any responses to this and if no one has any objections I'll come back later and reorder it.

Thanks!198.81.129.194 (talk) 15:56, 15 April 2016 (UTC)mjd

B-V is the most widely used best temperature calibrated index. Index UB may be not present in the measured index set, but BV will (almost) always be present. Interstellar extinction is usually expressed as color excess E(BV) or is frequently normalized to that excess. Orionus (talk) 19:48, 15 April 2016 (UTC)

B-V to Kelvin Formula

The equation provided doesn't give reasonably accurate answers for B-V approximately less than 0.

2605:E000:100D:8640:4415:6463:6330:9082 (talk) 07:08, 21 December 2019 (UTC)

Indeed Spica is a good example where the formula for Spica gives about 14500K where it's actual temperature is 20000K. — Preceding unsigned comment added by 2601:281:8200:2d50:a957:3e8f:ceb:a4cf (talk • contribs) 22:21, 26 February 2022 (UTC)

Additionally, the formula is inconsistent with the table on the right: the equation gives a temperature of 10125K for colour index 0 mag, while the table suggests one close to 9790K --88.68.135.214 (talk) 23:33, 29 September 2022 (UTC)

Can someone explain this?

This is the current equation:

$T=4600\,\mathrm {K} \left({\frac {1}{0.92\;B{\text{-}}\!V+1.6(-)}}+{\frac {1}{1.5\;B{\text{-}}\!V+0.62}}\right).$

I don't understand why the (-) symbol is there. When I ran this through Desmos, it didn't give an answer. Is there supposed to be a value here or should it be removed? Speed doesn't always mean quality. 400Weir (talk) 22:31, 14 August 2022 (UTC)

Green stars?

The table Quantitative color index terms mentions the colour green but unless I'm mistaken green stars do not exist. Perhaps this should be formulated in another way so that the term green can be avoided. AstroLynx (talk) 13:05, 20 October 2025 (UTC)