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diff --git a/noao/astutil/doc/astradius.hlp b/noao/astutil/doc/astradius.hlp new file mode 100644 index 00000000..f19a47ec --- /dev/null +++ b/noao/astutil/doc/astradius.hlp @@ -0,0 +1,138 @@ +.help astradius Jan96 astutil +.ih +NAME +astradius -- find images within a circle on the sky +.ih +USAGE +astradius images racenter deccenter epcenter radius +.ih +PARAMETERS +.ls images +List of images for which the radius to a point on the sky is to be +determined. +.le +.ls racenter, deccenter, epcenter +Right ascension in hours, declination in degrees, and epoch of a position +on the sky to use as the center of a circle. +.le +.ls radius +Search radius in arc seconds about the center position. +.le +.ls keywpars = "" (pset) +Parameter set defining the image header keywords. This task requires +keywords for the right ascension, declination, and epoch. If +there is no epoch in the image header keywords for the date of observation +and the universal time are used for the epoch. The default parameter +set (specified by the empty string) is \fBkeywpars\fR. +.le +.ls commands = "astutil$astradius.dat" +Command file used to compute the distance from the coordinate center +and print a result if the distance is less than the specified radius. +The command file uses the syntax described for \fBastcalc\fR. +Users may copy and modify this file if desired. +.le +.ih +DESCRIPTION +\fBAstradius\fR computes the spherical distance from a specified point on +the sky for each image in a list of images (\fIimages\fR). The point on +the sky is specified by the parameters \fIracenter\fR, \fIdeccenter\fR, and +\fIepcenter\fR which give a right ascension in hours, a declination in +degrees, and an epoch. Each image is required to have keywords for the +right ascension (hours), declination (degrees), and epoch. However, if no +epoch is defined in the image header then an epoch is computed from the +observation date and universal time. The spherical distance is compared to +a specified radius (\fIradius\fR) in arc seconds. If the distance is less +than the radius the image name and title are printed. + +The image header keywords giving the observation coordinates are defined +by the parameter set selected with the \fIkeywpars\fR parameter. +If no value is given then the parameters from the \fBkeywpars\fR +parameter set task are used. The keywords required are those +select by the \fIkeywpars.ra\fR, \fIkeywpars.dec\fR, and +\fIkeywpars.epoch\fR. If the epoch is absent or zero then the +keywords selected by \fIkeywpars.date_obs\fR and \fIkeywpars.ut\fR +are used to compute an epoch. + +\fBAstradius\fR is a simple script which calls \fBastcalc\fR. The +command file is specified by the parameter \fIcommands\fR. The +default file precesses the observation coordinates to the epoch +of the search center coordinates and then computes the spherical +distance between the search center and the observation. Finally +it tests the distance against the specified radius and prints +the image name and title if the observation is within the radius. +Users may copy the default command file and modify it. The +command syntax is described in the help for \fBastcalc\fR. +.ih +EXAMPLES +1. Page the script task and the command file. + +.nf + cl> page astutil$astradius.cl,astutil$astradius.dat + # ASTRADIUS -- Find images within a radius. + + procedure astradius (images, racenter, deccenter, epcenter, radius) + + string images = "" {prompt="List of images"} + string racenter = "" {prompt="RA center (hours)"} + string deccenter = "" {prompt="DEC center (degrees)"} + real epcenter = 2000. {prompt="Epoch of center"} + real radius = 60. {prompt="Radius in arc seconds"} + pset keywpars = "" {prompt="Keywords for RA, DEC, EPOCH\n"} + + file commands = "astutil$astradius.dat" {prompt="ASTCALC file"} + + begin + astcalc (commands=commands, images=images, table="", verbose=no) + end + + Print images which are within a given radius in the sky. + + # Get parameters. + racenter = clget ("astradius.racenter") + deccenter = clget ("astradius.deccenter") + epcenter = clget ("astradius.epcenter") + radius = clget ("astradius.radius") + ra = imget(clget("keywpars.ra")) + dec = imget(clget("keywpars.dec")) + + epoch = imget(clget("keywpars.epoch")) + if (str(epoch) == "" || real(epoch) == 0.) + date = imget(clget("keywpars.date_obs")) + ut = imget(clget("keywpars.ut")) + epoch = epoch (date, ut) + endif + + # Precess image coordinates to center epoch and compute separation. + radec = precess (ra, dec, epoch, epcenter) + ra1 = ra_precess (ra, dec, epoch, epcenter) + dec1 = dec_precess (ra, dec, epoch, epcenter) + sep = arcsep (racenter, deccenter, ra1, dec1) + + # Print result if within radius. + if (sep < real (radius)) + printf ("%-15s %s\n", $I, imget ("title")) + endif +.fi + +2. Find images within an arc minute of a particular position. + +.nf +cl> astradius +List of images: *.imh +RA center (hours): 13:31 +DEC center (degrees): 47:00 +Epoch of center (2000.): +Radius in arc seconds (60.): +obj0020.imh m51 B 600s +obj0021.imh m51 V 600s +obj0022.imh m51 R 600s +.fi +.ih +REVISIONS +.ls ASTRADIUS V2.11 +This task is new in this release. +.le +.ih +SEE ALSO +astcalc, hselect +.endhelp |