LINKOBJ2

Name

linkobj2

Purpose

Cross check source lists from one field and identify moving objects.

Description

Calling Sequence

linkobj2,tag,files

Inputs

tag - name of the field, should not contain any blanks
files - string array of file names for source lists to be linked.

Optional Input Parameters

Keyword Input Parameters

BADCOL - Array of column numbers, any source found within 2.5 pixels of
these columns will be discarded. Default = no bad columns.
CLEANAUTO - Flag, if set, all objects previously identified by "auto"
that are flagged with "?" and appear at the end of the list
will be removed from the list before any new linked objects
are added.
KEYLIST= - Name of a file containing a correspondence list. This list
associates a set of standard names with the actual keyword
names found in a FITS file header. If this keyword is
omitted, a default list is used, as if a file with the
following contents had been supplied:
AIRMASS K AIRMASS
DATE K DATE-OBS
DATETMPL T DD-MM-YYYY
EXPDELTA V 0.0
EXPTIME K EXPTIME
FILTER K FILTERS
FILENAME K CCDFNAME
OBJECT K OBJECT
UT K UT
The middle column is a flag. It may be K, for Keyword,
T, for Template, or V, for Value. If it is V, the contents
of the third field on that line should make sense for the
name in the first field.
KILLSRD - Flag, if set, this program will delete the pair of offending
srd files if the mean offset between the fixed sources is
out of range. When this happens, the .obj file is not
altered, an error message is printed on the screen, and
time-stamped information is written to linkobj2.err in
the current directory.
MAXDUPLERATE - Maximum motion rate permitted for a duple, in arcsec/hour.
The default is 5.0 arcsec/hour. Warning, making this too
big can create a very large number of false positive
detections.
MAXINCLINATION - Maximum motion angle from the ecliptic to be allowed.
Used for duple only. Default=no limit
MAXMAGDIFF - Maximum magnitude difference allowed between two measurements
to be tagged as a moving object. This is used ONLY for
checks of duples. The default value is 1.0 mag. However,
the allowed difference can be larger if the photometric
errors are large. The test is to keep objects whose
variation is 3-sigma or less or magdiff less than maxmagdiff
MAXOBJ - Maximum number of objects to report as linkages. Default
is to report everything. Only the first MAXOBJ objects
will be reported. This can safeguard against the situation
where a bad astrometric solution leads to a very large number
of linkages.
MAXOFFSET - Maximum offset post-correlation in pixels to flag a bad
overlay. Default is 1.5 pixels. Use the feature with
extreme caution. It's very easy to let garbage through if
you make this too big.
MAXRATE - Maximum motion rate permitted for a tripet, in arcsec/hour.
The default is 50.0 arcsec/hour.
MINHITS - When linking 3 or more frames, this variable controls the
minimum number of coincident hits that are required to
flag the link as valid. Default=3.
MINRATE - Minimum motion rate permitted for a tripet, in arcsec/hour.
The default is 1.0 arcsec/hour.
PATH - Optional path for original image directory.
If not specified, the current directory is used.
SNRTHRESH - Signal-to-noise ratio threshold. Default is to use all objects
in the input lists. If you provide a threshold, all objects
with SNR less than this will be excluded from the linking.
SRDDIR - Directory for the srd files, default=current directory

Outputs

Keyword Output Parameters

Common Blocks

Side Effects

Restrictions

Procedure

Modification History

98/03/11, Written by Marc W. Buie, Lowell Observatory
2000/02/08, MWB, numerous bug fixes and enhancements.
2000/03/09, MWB, minor bug fix for n-tuples and added MINHITS
2000/05/01, MWB, added MAXOFFSET keyword
2000/07/31, MWB, added MAXOBJ keyword
2000/10/18, MWB, added SNRTHRESH keyword
2003/10/01, MWB, converted my Delfile call to system file_delete routine
2004/06/24, MWB, added MAXMAGDIFF keyword
2010/07/19, MWB, minor tweak to accomodate change to frmdxdy
2015/03/28, MWB, changed error logging to use logerror procedure
Also changed to generate obj files even with an error
this change now bypasses the /KILLSRD flag operation.
2016/05/29, MWB, added SRDDIR keyword