This allows changes of the values of some of the non-aperture shape related parameters.
The INNER and OUTER parameters define the size of the annulus to be used in the automatic sampling of the sky. The annulus has the same elliptical shape as the object aperture, but is larger by the factors given by INNER and OUTER. These two parameters are given in terms of multiplicative factors of the semi-major axis of the object aperture. Thus an INNER radius of 1 means that the sky annulus starts where the object aperture ends. The annulus thus grows and shrinks with changes to the object aperture.
The PADU parameter defines the number of photons for each interval of the data. Multiplying the data value in each pixel by PADU gives the number of photons recorded (after correcting for BIASLE). If this parameter is unknown then leave it at 1. It is necessary to provide an estimate of this number if optimal extraction is to be carried out correctly.
The SKYMAG parameter specifies the magnitude to be given to the sky when calculating the magnitude of the object. The magnitude of the object is calculated from where signal is the brightness of the object minus sky in photons. This parameter is not used if USEMAGS is set to FALSE (in this case the output is not in magnitudes).
The BIASLE parameter gives the level in data units of any offset in the bias level per pixel. This is needed if there is any non-photon source of background, and proper photon statistics are required. If this parameter is unknown then leave it at 0.
The SATURE parameter is the saturation level for the image in data units. If there are any pixels in the object aperture with values greater than the saturation level then this is indicated by an error code 'S' in the final column of the output table. The object magnitude is calculated with the saturated pixel included in the result. So changing the value of this parameter will not change the results but will alter the number of objects flagged in the output file.
The CLIP parameter is clipping radius of the weight mask used in optimal extraction. This is needed if optimal extraction is enabled and defaults to 5 pixels. If optimal extraction is not enabled (using the X command) then the CLIP parameter will not appear in the list when the options command is issued.
The SEE parameter is a rough estimate of the seeing in the CCD image in pixels. This is used by the optimal extraction algorithm for an initial estimate of the FWHM of the point spread function (PSF) during fitting. This parameter defaults to 2 pixels, and again if optimal extraction is not enabled then this parameter will not appear in the list when the options command is issued.
PHOTOM --- A Photometry Package