NAME

double -- Process double-star observations from transfer function data.

USAGE

double intable1 intable2 outtable out_fit x_or_y

DESCRIPTION

This task reads transfer-function data for a double star and transfer-function data for a single reference star from SDAS tables, and then searches the parameter space for good initial estimates of the zero-point offset, separation, and relative brightnesses of the stars. Either the X-coordinate or Y-coordinate data may be processed.

PARAMETERS

intable[file name template]

Name of the input table that contains the observations. If X-coordinate data are being processed, i.e., if the x_or_y parameter is set to x, then the X coordinates (in arcseconds) and the normalized fine error signal (FES) are read from columns with names X and FESX respectively. If Y-coordinate data are being processed, i.e., the x_or_y parameter is set to y, then columns Y and FESY are read.

intable[file name template]

Name of the input table containing reference transfer function data for the single reference star. The coordinates (in arcseconds) and normalized fine error signal are read from columns with names X and FES respectively, regardless of whether X or Y coordinates are being processed.

outtable [file name]

File name for the output table, which will provide input parameters to the gaussfit task. The relative brightnesses of the two stars, their zero-point offset, and their separation as determined by the double task will be written into the first row with column names a, b, xoff, and sep, respectively. A copy of the single-star reference table (intable2) will also be written to outtable. Outtable contains the following columns:

COLUMN  CONTENTS
======  ========
nmodel	row number
xmodel	independent variable (X or Y coordinate in arcsec) of
	reference single-star transfer function
ymodel	dependent variable (normalized fine error signal) of
	reference single-star transfer function
a	relative brightness of the first star (first row only)
b	relative brightness of the second star (first row only)
xoff	offset of independent variable of observations (first row only)
sep	separation (arcsec) between stars (first row only)
modpts	the number of rows in 'outtable' (first row only)

out_fit [file name]

File name of the output table for evaluation of fit to data. If out_fit is not null, then a fit to the observed data will be constructed using the determined parameters and the single-star transfer function data. The fit will be evaluated at the values of the independent variable in intable1 (the observations table). The independent variable and evaluated function will be written to out_fit using column names X and FIT respectively.

x_or_y = x [string, allowed values: x | y]

Process which coordinate?

(nfit = 3) [integer, min=1, max=3]

How many parameters are to be fit?

If nfit = 1, then only the zero-point offset will be fit. If nfit = 2, then the zero point and separation will be fit, and the relative brightnesses of the two stars will be held fixed.

(brightness = 0.6) [real, min=0., max=1.]

Relative brightness of one star.

(separation = 0.1) [real, min=0.]

Separation between stars (in arcseconds).

(verbose = yes) [boolean]

Print results to the terminal screen?

EXAMPLES

1. The lines following the command (first line), show the 
output from 'double' when 'verbose' is set to 'yes'.
	fg> double obs single test "" x
	Initial guess:
	    Star brightnesses: 0.600 0.400
	           Separation: -0.03 Arc-sec
	    Zero-point offset: 0.040 Arc-sec

BUGS

SEE ALSO