Posted by Richard Miles at 17:47 on 2014 Jan 05
Alex – The lightcurve amplitude of Vesta is small, like you say, at between 0.08-0.19 mag depending on its heliocentric longitude for the present apparition. That of Ceres ranges from 0.02-0.06 mag.By doing colour difference magnitudes, such as (B-R) for Vesta MINUS (B-R) for Ceres, any variation in general brightness of the two objects cancels out and we are left with colour changes only. Since DSLRs do 3 colours at a time, and these asteroids are both brighter than magnitude 8.5 (Vesta reaches mag 5.7 in April), these cameras are pretty ideal tools for the job. The only thing to watch will be to use a short enough exposure time to avoid saturating pixels in the image of Vesta.I’ll look to write a short ‘How To’ crib sheet for folk planning on having a go. If several people tried it then the combination of all would be better than an effort by one person only.There might be a spin-off too in that it could kick start more use of DSLRs for variable star observations as well as those of asteroids!