Does aperture photometry on buffer im using input star file. Unlike standalone DAOPHOT, a photometry table which gives aperatures, etc., is not used. The user can specify pixel radii (up to 30 different values) with the RAD= keyword to give the desired radii for aperture photometry. The GAIN= and RN= keywords need to be used to give proper error estimates. With the RAD= keyword, the SKY is assumed to be 0 unless it a sky value is supplied with the SKY= keyword, or unless two annulus radii are specified with the SKYRAD= keyword (which is the normal mode of operation). A series of aperture radii in an aritmetic progression can be specified in shorthand using RAD=-naper,startaper,deltaaper (note that this format is recognized by a NEGATIVE naper), where naper is the desired total number of apertures, startaper is the size of the first aperture, and deltaaper is the amount added to the previous aperture size.
The keyword SKY= can be used to set a sky value, used for all stars. Normally, however, one wishes to allow for possible background variations across the frame, and a sky value is computed from an annulus around each object; the size of the annulus is specified using the SKYRAD=r1,r2 keyword. The default mode of operation uses the DAOPHOT MMM routine to compute a sky value based on an estimate of the mode of the distribution within the sky annulus. Alternatively, the keyword MEAN forces a mean sky value to be used, and the 3SIG keyword computes an iterated mean with 3-sigma rejection. The keyword SKYINT will compute a sky value for each star, then prompt the user to enter a desired value for each star.