Photometry Keywords

The Photometry Keywords command is used to set keyword names used by the photometry tools to load Properties from the image headers. This command uses the dialog shown below. If these keywords are not present in the image headers, some of them that do not change can be set in the images using the Modify Keywords command.

This command is operated using the Photometry Keywords page of the Aperture Photometry Properties dialog. The dialog is opened by clicking on the Aperture Photometry toolbar..

This dialog is used to set the FITS style header keywords and specify the format that certain keywords will use in your images. For some of these keywords, the format may be either an angle string or a value in decimal degrees.

The first 6 keywords are used for computing the airmass of the observation. If the airmass cannot be calculated, or if bad keyword values cause the value to be impossible, then the result is reported as 0.0 in the Apphot Pane.
The last 3 keywords are used for computing the photometric errors and zero point value.

Photometry Keyword Properties
Right Ascension	The right ascension coordinate in units of either decimal degrees or HMS. You must select the coordinate format from the adjacent list box. Decimal degrees is the standard FITS representation for angles.
Declination	The declination coordinate in units of either decimal degrees or DMS. You must select the coordinate format from the adjacent list box. Decimal degrees is the standard FITS representation for angles.
Site Longitude	The longitude of the observing site in units of either decimal degrees or DMS. You must select the coordinate format from the adjacent list box.
Flip Sign	This option flips the sign of the longitude specified in the image header. Mira expects longitude to be positive when measured west of Greenwich, England (as in the Americas). Check this box if the longitude in the image header is specified as negative west of Greenwich or vice versa.
Site Latitude	The latitude of the observing site in units of either decimal degrees or DMS. You must select the coordinate format from the adjacent list box.
UT Date	The UT date of observation. Usually this quantity uses the DATE-OBS keyword.
UT Time	The UT time of observation. Usually this quantity uses the DATE-OBS keyword but you can also specify another keyword such as TIME-OBS.
Camera Gain	The camera gain value in units of electrons per ADU (or Digital Number, DN). Usually, this quantity uses the GAIN keyword.
Readout Noise	The camera's readout noise in units of electrons. Usually, this quantity uses the RDNOISE keyword.
Exposure Time	The exposure time in units of seconds. Usually, this quantity uses the EXPTIME keyword.

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