ASTSOLVE

Name

astsolve

Purpose

Solve for astrometric transformation from image to sky coordinates.

Description

Calling Sequence

astsolve,x,y,xi,eta,terms,renormfac,bad,cxi,ceta

Inputs

x - Image x-coordinate (should be "normalized" to range from -1 to 1)
y - Image y-coordinate (should be "normalized" to range from -1 to 1)
xi - Standard tanget plane coordinate (should be in arcsec)
eta - Standard tanget plane coordinate (should be in arcsec)
terms - Which fitting terms to use (see ASTTERMS.PRO)
renormfac - Re-normalization factor for converting from normalized x,y to
the original x,y values.
bad - array of flags that mark bad data on input (modified).

Optional Input Parameters

Keyword Input Parameters

EDIT - Flag, if set allows interactive bad point editing.
MAXPASS - Maximum number of passes allowed when weeding out bad points
during the fit. (default=1000)
NOAUTOCLEAN - Flag, if set suppresses all attempts to weed out bad points.
XFLIP - Flag, if set flips x axis plot when editing bad points.
YFLIP - Flag, if set flips y axis plot when editing bad points.
FORCETERMS - String array, if provided, is a list of terms (from "terms"
input variable) that will be forced to a constant
value rather than being fitted.
FORCEVAL - This can either be an array of values or a scalar string.
If it is an array it must be a Nx2 array where N matches the
length of FORCETERMS and is used as the forced values in
the same order as FORCETERMS. Row 0 of this array holds
the forced xi term values and row 1 holds the eta terms.
If it is a string, this is taken to be the name of a file
in the current directory that contains the fit
coefficients. This file is the same format as that
used for storing normal fitting coefficients (see
rdastfc.pro for details). However, this file uses the
first field to identify the name of the filter for
the coefficients rather than the filename as is normal
for this type of file.
The default value of this keyword is 'forcecoeff.dat'.
FORCEFILTER - String value of the name of the filter. This is relevant
only when using a file for the coefficients. If the
file contains information for a single filter then
that filter name is the default value. However, if there
are two or more filters in the file then this keyword
must be supplied.
SILENT - Flag, if set suppresses all (non-error) printed output messages.
Does not affect PROGRESSINFO

Outputs

cxi - coefficients of xi fit.
ceta - coefficients of eta fit.
bad - array of flags that mark bad data on output.

Keyword Output Parameters

WORSTRESID - Worst residual in "good" data in either axis (arcsec)
XISCAT - Scatter of xi fit (arcsec).
ETASCAT - Scatter of eta fit (arcsec).
CXISIG - Uncertainty of the xi fit coefficients.
CETASIG - Uncertainty of the eta fit coefficients.
XICOVAR - covariance matrix of the xi fit coefficients.
ETACOVAR - covariance matrix of the eta fit coefficients.
PROGRESSINFO - string array with the printed information

Common Blocks

Side Effects

Restrictions

Procedure

Modification History

98/03/13, Written by Marc W. Buie, Lowell Observatory
98/11/23, MWB, added renormfac and fixed documentation
2000/09/14, MWB, added WORSTRESID keyword
2001/08/27, MWB, changed to auto-scale errors with /edit
2003/06/24, MWB, changed call to MARKDATA to use new features.
2003/10/27, MWB, fixed subtle bug during bad point cleanup. The test
was done on O-C against the std deviation of a
robust mean. The test needs to remove the mean of
the surviving sample.
2006/02/03, MWB, added XISCAT and ETASCAT output keywords.
2009/07/14, MWB, added CXISIG, CETASIG, XICOVAR, ETACOVAR output keywords.
2009/12/02, MWB, calling seqeunce CHANGED! xiterms and etaterms
are now consolidated into a single input argument.
2009/12/23, MWB, Major enhancement to add the ability to force some or
all of the terms. This mode is supported by the new
keywords, FORCETERMS, FORCEVAL, and FORCEFILTER.
2015/04/10, MWB, Added PROGRESSINFO output keyword