RDASTFC

Name

rdastfc

Purpose

Read an astrometry fit coefficient file.

Description

File I/o

Calling Sequence

rdastfc,file,ffn,ftype,xc,yc,prot,renormfac,cra,cdec,photzp, $
terms,coeffarr,ncoeffs,nlines

Inputs

file - Input file name to be read.

Optional Input Parameters

Keyword Input Parameters

FNCENTERS - File with image centers. (Default=centers.dat)

Outputs

Each of these ouputs are vectors or arrays. The length of the vectors or
the number of rows is equal to the number of fit coefficient sets in
the file. For arrays, the dimensions are [nlines,10]
ffn - File name for this fit.
ftype - Type of fit (eta or xi)
xc - X center of array
yc - Y center of array
prot - Pre-rotation of raw coordinates (degrees)
renormfac- Renormalization factor used for solution. If not known it
will be set to -1
cra - Center right acension (radians)
cdec - Center declination (radians)
photzp - Photometric zero-point for this image. If the value is
99.0 the zero point has not been determined. This will
allow you to later compute a real magnitude from instrumental
magnitudes on the frame.
terms - Term names that are used (see astterms.pro for more information).
string vector size is [ncoeffs]
coeffarr - Array of astrometric fit coefficients (see astterms.pro)
array size is [nlines,ncoeffs]
ncoeffs - Number of fitted coefficients (scalar)
nlines - Number of coefficients read from file (scalar).

Keyword Output Parameters

VERSION - Version tag of file that was read.
ERROR - Flag, set if error found during read.

Common Blocks

Side Effects

Restrictions

All of the solutions in the file must have the same number of terms.

Procedure

The solution is a two-step conversion. You start with raw coordinates
that typically relate to the original position in the native coordinate
system for the device. The first transformation step is to convert
to another system related to the first by a translation and rotation.
e.g. xp = ( (x-xc)*cos(prot) + (y-yc)*sin(prot) ) / renormfac
yp = ( -(x-xc)*sin(prot) + (y-yc)*cos(prot) ) / renormfac
The astrometric transformation then maps xp,yp to ra,dec.

Modification History

1999/04/15, Written by Marc W. Buie, Lowell Observatory
2000/01/19, MWB, added version 1.1 support (now includes photzp)
2002/04/09, MWB, changed from Str_Sep to strsplit
2005/06/28, MWB, fixed bug when reading an empty file.
2009/08/04, MWB, added prot and renormfac variables thus changing the
calling sequence (sorry)
2009/12/01, MWB, moved up to version 1.3, calling sequence slightly
different again. (terms was flagarr, some returned
values have a smaller rank). Added ERROR output.