CApphot Data Members

CApphot Properties

This CApphot class properties are used for passing values to and from the Mira photometry routines. All properties have default values that are either reasonable or allow the methods to work as expected. You can get or set these values using the member name and dot syntax. Data members set by the Measure and GetImageParams methods can be fetched using the dot syntax and member name or using the colon syntax with an Accessor method. For example suppose your script uses a CApphot object A. Then you can use A.bRemoveBg or A.nMag to set these properties. Similarly, the nNetCount member is set by the Measure method, and its value can be accessed using A.nNetCount or A:NetCount().

Properties Returned by CApphot

The properties below must be set before calling Measure.

Measurement Properties
bVerbose	Controls whether the measurement is silent or lists verbose information. Defaults to false (silent).
bRemoveBg	Controls whether the background value is removed from the raw measurement. This value defaults to true. The background parameters are set using the SetBgMethod method.
bCalcMag	Controls whether the instrumental magnitude is calculated from the net count. If this parameter is set to false, the Measure method sets returns a value in nNetCount but does not set nMag. This member defaults to true.
bApplyZeroPt	Controls whether the photometric zero point (the nZeroPt member) is used to return an instrumental magnitude in the nMag member. The default setting is true, which applies the zero point.
bUseZeroPtErr	If set to true, the photometric zero point error in nZeroPtErr is applied to the values of nMagError and nMagErrorT. The default is false.

Instrumental Properties
nGain	The camera gain, measured in electrons per Count, or electrons per ADU (default 1.0). This value may be retrieved from the image using CImage:Gain method, or it can be automatically set using the GetImageParams method.
nReadNoise	The image readout noise, measured in electrons (default 1.0). This value may be retrieved from the image using CImage:KwdGetNum("RDNOISE") or CImage:KwdGetNumEx("RDNOISE"), or it can be automatically set using the GetImageParams method.
nExptime	The image exposure time, measured in seconds (default 1.0). This value may be retrieved from the image using the CImage:Exptime method, or it can be automatically set using the GetImageParams method.
nZeroPt	The photometric zero point for the image, measured in magnitudes (default 0.0). This value may be retrieved from the image using CImage:KwdGetNum("ZERO-PT") or CImage:KwdGetNumEx("ZERO-PT"), or it can be automatically set using the GetImageParams method.
nZeroPtErr	The uncertainty of the photometric zero point for the image, measured in magnitudes (default 0.0). This value may be retrieved from the image using CImage:KwdGetNum("ZEROPERR") or CImage:KwdGetNumEx("ZEROPERR"), or it can be automatically set using the GetImageParams method.
Aperture Properties
nRadius1	The radius of the object measuring aperture, measured in pixels (default 3).
nRadius2	The radius of the inner background measuring aperture, measured in pixels (default 10).
nRadius3	The radius of the outer background measuring aperture, measured in pixels (default 16).
nEllipticity	The ellipticity of the aperture set (default 0, or circular). This measures the value 1 - b/a, where a is the semimajor axis and b is the semiminor axis of an ellipse. A circle has a = b.
nTheta	The angle of the semimajor axis of the aperture set (default 0). This is relevant only when elliptical apertures are used by setting a value of nEllipticity > 0.

Value Passed to CApphot

The properties below are returned to the script by the Measure method. You can access them using the names in the table below or by using Accessor Methods of similar name; the choice is yours and is usually just a matter of programming style.

nX	The X position of the center of the measure apertures, measured in pixel coordinates. This value also can be fetched using the class method X.
nY	The Y position of the center of the measure apertures, measured in pixel coordinates. This value also can be fetched using the class method Y.
nStatusCode	An integer number indicating the status returned by the GetImageParams method. This value also can be fetched using the class method GetStatusCode.
sErrMsg	Used by the Measure method to indicate "Success" or an error message. The error message also can be fetched using the class method GetErrMsg.
nNetCount	The net count for the object, measured in counts (or "ADU" or "DN"). If the bRemoveBg flag is true, this is the net count above the background. Otherwise, it is the total count above zero. This value also can be fetched using the class method NetCount.
nNetCountErr	The uncertainty in the net count for the object, measured in counts (or "ADU" or "DN"). This value is based on the background noise and photon statistics. This value also can be fetched using the class method NetCountErr.
nNetCountErrT	The theoretical uncertainty in the net count for the object, measured in counts (or "ADU" or "DN"). This value is based on instrumental parameters and photon statistics. This value also can be fetched using the class method NetCountErrT.
nBgValue	The background value per pixel, measured in counts (or "ADU" or "DN"). If the bRemoveBg flag is true, this value was subtracted from the total to calculate nNetCount. This value also can be fetched using the class method BgValue.
nBgValueErr	The error in the background value (per pixel). This is a 1-sigma mean error, not the error of the mean background. The value is measured in units of counts (or "ADU" or "DN"). If the bRemoveBg flag is true, this value was subtracted from the total count to calculate nNetCount. This value also can be fetched using the class method BgValueErr.
nMag	The measured magnitude of the object. If the bApplyZeroPt flag was true, then this includes the photometric zero point set in the nZeroPt value. This value also can be fetched using the class method Mag.
nMagError	The random error in the value of nMag as calculated from the noise measured in the background sample. If the bApplyZeroPtErr flag was true, then this includes the photometric zero point error set in the nZeroPtErr value. This value also can be fetched using the class methods MagError or MagErr.
nMagErrorT	The random error in the value of nMag as calculated using only the instrumental values but not the actual noise measured in the background sample. If the bApplyZeroPtErr flag was true, then this includes the photometric zero point error set in the nZeroPtErr value. This value also can be fetched using the class methods MagErrorT or MagErrT.
nSnRatio	The Signal to Noise Ratio of the signal measured inside the object aperture of radius nRadius1. This value is computed from the total signal and the signal error included in nMagError. This value also can be fetched using the class method SNR
nSnRatioT	The Signal to Noise Ratio of the signal measured inside the object aperture of radius nRadius1. This value is computed from the total signal and the theoretical signal error included in nMagErrorT. This value also can be fetched using the class method SNRT.