negative magnitude in PHOT
Nakisa Nooraee wrote on Nov 15, 2010
Hi, I have two questions about PHOT.
First , I am doing photometry on some stars in M31. PHOT gave me -23 . I don't know where this minus comes from!
second, how can I get error bar on the magnitude value with PHOT?
Best,Nakisa
First , I am doing photometry on some stars in M31. PHOT gave me -23 . I don't know where this minus comes from!
second, how can I get error bar on the magnitude value with PHOT?
Best,Nakisa
Mike Fitzpatrick wrote on Nov 15, 2010
There's not really enough information in your post to comment specifically. The magnitude is computed using a 'zero point' value from the 'photpars.zmag' parameter. This is normally set to 25.0, but if you reset it to zero it might explain your large value.
Otherwise, errors are reported as the 'merr' column in the output table, specifically this is derived as
See the help page for details.
Otherwise, errors are reported as the 'merr' column in the output table, specifically this is derived as
merr = 1.0857 * error / fluxSee the help page for details.
Last post on Nov 15, 2010