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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.
x
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.
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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.
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The last 3 keywords are used for computing the
photometric errors and zero point value.
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Photometry Keyword Properties
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Right Ascension
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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.
The FITS standard is for right ascension to be
held in the CRVAL1 keyword and
specified in decimal degrees. A common non-conforming usage is with
the RA keyword and specified in
HMS units, as hh:mm:ss.sss.
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Declination
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The declination coordinate in units of either
decimal degrees or DMS. You must select the coordinate format from
the adjacent list box.
The FITS standard is for declination to be held in
the CRVAL1 keyword and specified in
decimal degrees. A common non-conforming usage is with the
RA keyword and specified in
HMS units, as dd:mm:ss.sss.
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Site Longitude
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The longitude of the observing location 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.
The FITS standard is for longitude to be held in
the SITELONG keyword and specified in
decimal degrees. A common non-conforming usage is with the
LONGITUD keyword and specified in
HMS units, as hh:mm:ss.sss.
NOTE: The longitude is negative west of the Prime
Meridian at Greenwich, England (e.g., the Americas), as per the
World Geodetic System specification WGS84. Incorrect longitude sign
can be accommodated using the Flip Sign
option.
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 Flip Sign
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This option flips the sign of the longitude
specified in the image header. Mira expects West longitude to be
negative (see the description of "Site Longitude"). If west
longitude is incorrectly specified as positive, or vice versa,
check this box.
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Site Latitude
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The latitude of the observing location in units of
either decimal degrees or DMS. You must select the coordinate
format from the adjacent list box.
The FITS standard is for latitude to be held in
the SITELAT keyword and specified in
decimal degrees. A common non-conforming usage is with the
LATITUDE keyword and specified in
HMS units, as hh:mm:ss.sss.
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UT Date
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The UT date of observation.
The FITS standard is for date and time to be
combined in the DATE-OBS keyword with
the format yyyy-mm-ddThh:mm:ss.sss.
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UT Time
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The FITS standard is for date and time to be
combined in the DATE-OBS keyword with
the format "yyyy-mm-ddThh:mm:ss.sss".
FITS images saved before Jan 1, 2000 ("Y2K") use the obsolete
keyword TIME-OBS with the format
hh:mm:ss.sss.
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Camera Gain
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The camera gain value in units of electrons per
ADU (or Digital Number, DN). Usually, this quantity uses the
GAIN or EGAIN keyword.
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Readout Noise
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The camera's readout noise in units of electrons.
Usually, this quantity uses the RDNOISE
or RNOISE keyword.
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Exposure Time
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The exposure time in units of seconds. The FITS
standard is for exposure time to be held in the EXPTIME keyword.
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Related Topics
Aperture Photometry
Aperture
Photometry Properties
FITS Keywords
Calculate Julian Date
Photometric Measurement Definitions
Photometric Error Definitions
Mira Pro x64 User's Guide, Copyright Ⓒ 2023 Mirametrics, Inc. All
Rights Reserved.
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