CApphot Class Description

The CApphot class manages the operation of aperture photometry routines. These routines are used for computing the total brightness of a point sources. For astronomical applications, this is used to measure stars and other objects that are unresolved or of small angular extent. The aperture may be a circle or an ellipse. The background is subtracted from the measurement and may be computed locally or assigned a specified value.

Usage

Construction

Object = new_apphot()

Object = CApphot:new()

Destruction

Object:delete()

Properties

This class contains numerous properties that describe the measurement. These are used to pass data to and from the photometry functions. See CApphot Properties. Values returned by the GetImageParams and Measure methods also used class properties and may be retrieved using either the properties or the Accessor Methods below.

Creation - Non-class Functions

This function is normally used to create a new CApphot object as an alternative to the class-based new method.

new_apphot

Creates a new instance of a CApphot object.

Construction and Destruction - Class Methods

new	Creates a new instance of the CApphot class. There are 2 constructor formats.
delete	Deletes the instance of the CApphot object.
Copy	Copies the properties of this CApphot object to a new CApphot object.

Operations

GetImageParams	Reads the image header and fetches the values of camera gain, readout noise, exposure time, and the photometric zero point and its error. These values are returned as class properties. See CApphot Properties.
Measure	Performs an aperture photometry measurement at a (column,row) coordinate in an image.
SetBgMethod	Sets the method used to evaluate the background in the Measure method. Four options are provided: mean, median, mode, and value.

The following table describes "accessor" methods that return the parameters of a measurement. These methods return CApphot properties of similar name.

GetStatusCode

Returns an integer number indicating the status returned by the Measure and GetImageParams methods.

The Measure method returns false if an error occurred. A negative error number can be retrieved using GetStatusCode.

The GetImageParams method returns false if an error occurred. The various errors are bit-wide OR-ed into a single positive number which is returned by GetStatusCode. The errors may be sorted out using the BitTest function.

GetErrMsg

Returns a string indicating "Success" or the error message generated by the photometry method (see GetStatusCode).

Accessor Methods

These methods return (access) the values of class properties.