iraf.net

Hi Ian,On Thu, 1 Sep 2005, Ian Thompson wrote:> In the FXCOR program RV package), should the heliocentric corrections
> applied to get the object velocity agree with those calculated
> with the RVCORRECT program for the same object star? To first order, yes. Small differences come about because
FXCOR uses the mid-point time of observation (e.g. DATE-OBS + EXPTIME/2)
whereas RVCORRECT simply uses the DATE-OBS keyword. If a time isn't
supplied by date-obs the UT keyword is read, but the difference comes
from taking into account the exposure time. Cheers,
Mike Fitzpatrick