Hi, I've been looking for some of the early work done on transitting theory for the detection of extrasolar planets. I am especially interested in the calculation of the transitting time. The only equation I have so far come across is... T/P=(1/pi)*arcsin(R*/a) in the paper by Rivera et al 2005 on the detection of GJ 876d. It strikes me that this equation (although not formally stated in the paper) is only an approximate (and was unreferenced so I can't trace where it came from). If anyone knows of a more exact equation and some work which has been done on this subject, please post a reference. Thanks.