.help pairmass Nov01 noao.obsutil
.ih
NAME
pairmass -- plot the airmass for a given object
.ih
USAGE
pairmass
.ih
PARAMETERS
.ls ra
The right ascension of the object in hours.
.le
.ls dec
The declination of the object in degrees.
.le
.ls epoch=INDEF
The epoch of the coordinates in years.
.le
.ls year
The year of the observation.
.le
.ls month
The month of the observation (a number from 1 to 12).
.le
.ls day
The day of the month of the observation.
.le
.ls observatory = "observatory"
The observatory identifier in the observatory database.  See the
help for \fBobservatory\fR task for more information.
.le
.ls timesys = "Standard" (Universal|Standard|Siderial)
Time system for the plot or output list.  The choices are
"Universal" for universal time, "Standard" for standard time (where
the time zone is determined from the observatory database), and "Siderial"
for the siderial time.
.le

.ls resolution=4
The number of UT points per hour for which to calculate the airmass.
.le
.ls listout=no
List, rather than plot, the airmass versus time?  Only airmasses
below that given by the \fIwy2\fR parameters are listed.
.le
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PLOT PARAMETERS
.ls wx1=-7., wx2=7., wy1=0., wy2=5.
The range of window (user) coordinates to be included in the plot.
If the range of values in x or y = 0, the plot is automatically
scaled from the minimum to maximum data values along that axis.
The times are available from -24 hours to 48 hours so one can use
negative numbers to plot hours from midnight or in actual hours.
.le
.ls pointmode = no
Plot individual points instead of a continuous line?
.le
.ls marker="box"
If \fBpointmode\fR = yes, the marker drawn at each point is set with this
parameter.  The acceptable choices are "point", "box", "plus", "cross",
"circle", "hebar", "vebar", "hline", "vline", and "diamond".
.le
.ls szmarker = 0.005
The size of the marker drawn when \fBpointmode\fR = yes.  A value of 0
(zero) indicates that the task should read the size from the input list.
.le
.ls logx = no, logy = no
Draw the x or y axis in log units, versus linear?
.le
.ls xlabel="default"
Label for the X-axis.  The value "default" uses the specified time system.
.le
.ls ylabel="Airmass"
Labels for the Y-axis.
.le
.ls title="default"
Title for plot.  If not changed from "default", a title string consisting
of the date, observatory, and  object position is used.
.le
.ls vx1=0., vx2=0., vy1=0., vy2=0.
NDC coordinates (0-1) of the plotting device viewport.  If not set
by the user, a suitable viewport which allows sufficient room for all
labels is used.
.le
.ls majrx=5, minrx=5, majry=5, minry=5
The number of major and minor divisions along the x or y axis.
.le
.ls round = no
Round axes up to nice values?
.le
.ls fill = yes
Fill the plotting viewport regardless of the device aspect ratio?
.le
.bp
.ls append = no
Append to an existing plot?
.le
.ls device="stdgraph"
Output device.
.le
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DESCRIPTION
The airmass is plotted over a specified set of hours for a given
observatory.  The observatory is specified by an identifier as given
in the observatory database.  See the help for "observatory" for more
information about the database and identifiers.

The results can be shown in universal, standard, or siderial time.
The standard time simply adds the time zone from the observatory
database tothe universal time and so there is no explicit facility
for daylight savings time.  The times are computed in the range
-24 hours to +48 hours.  By setting the \fIwx1\fR and \fIwx2\fR
parameters one can plot either in hours relative to 0 in the specified
time system or as positive hours.  This simple task does not support
axis labeling which wraps around.

The list output prints date, observatory, object coordinates, and
the time system.  This is followed by the time sorted between 0 and 24
and the airmasses.  The list only includes airmasses below the
value specified by \fIwy2\fR.
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EXAMPLES
To plot the airmass for M82 from Kitt Peak for Groundhog's Day in 1992:

.nf
    pairmass ra=9:51:42 dec=69:56 epoch=1950 year=1992 month=2 day=2
.fi

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SEE ALSO
observatory, airmass, setairmass, graph
.endhelp
