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On Mon, 23 Jan 2006, Brad Cavanagh wrote: > I'm having some trouble getting aperture photometry working through GAIA > on OS X. If I set up an aperture around an object, leaving everything else > to be the default, it looks like the centroiding goes astray and I get > strange results. > > As an example, I'm using the file at > http://www.jach.hawaii.edu/~bradc/starlink/gf20050817_11_mos.sdf. If I > draw an aperture centered on the object at 139,630 with a 20-pixel > semimajor axis, then hit 'calculate results', the X/Y position either > doesn't change or it goes off to some position that clearly isn't centered > on the object. Further, values like mean count or sum in aperture come out > negative, when they should be blazingly positive. > > I've tried this using autophotom from the command-line and it gives > roughly the same results -- the position doesn't change, but the magnitude > is 50.000 and the magnitude error is 99.999. It also gives a warning > saying "Problems duringcentroiding [sic]". > > This all works fine on Linux. Centroiding via GAIA's Pick Object works > fine on this object. Hi Brad, sorry that was an issue with the origin information being used by GAIA. The photometry toolbox works in PIXEL coordinates, so in fact 139,630 isn't anywhere near an object, hence the bad results. You'll need to rebuild GAIA (from scratch is best) to get the fix. Cheers, Peter.