Re: Calculation of mag errors

[droege@snapmail.us]

The last two years of running were made with the values below in the
stars.param

Tom

>
>> Now that you have done all the dirty work of
>> setting up the statistics for the annulus, is this
>> a good time to revisit estimating this error?
>> One might be able to estimate things like
>> background curvature - if too big, go to a
>> smaller annulus and accept the higher random
>> error in exchange for the smaller systematic
>> error. I never tried to do this: I couldn't see how
>> to do it in a manner that was not horribly
>> sensitive to nearby confusing stars.
>
>   Hmmm.  I don't see any easy way to add this sort
> of decision-making intelligence to the pipeline
> without a _lot_ of work.
>
>   What _is_ easy is to modify one of the parameter
> files: a simple ASCII text file, not code.  The
> "stars.param" file has a section which looks like this:
>
> # parameters controlling the "phot" program
> apers         { V { 4 } }    { I { 4 } }
> sky_inner     { V  10   }    { I  10   }
> sky_outer     { V  20   }    { I  20   }
> readnoise     { V     15   } { I     15   }
> gain          { V      2.4 } { I      2.4 }
> saturate      { V  20000   } { I  20000 }
>
>
>   One can place several aperure radii into the first parameter,
> so that all stars are measured through several different
> apertures, and the results all processed.  One could
> then look at the results after one night, or one week,
> and figure out which value gives the best result for a given
> camera under typical conditions.  I suspect that Tom
> has done some optimizing of this sort ....
>
>
>                                    Michael Richmond
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