BAIT manual page

NAME

findmatch - determines rotation and offset of .coo or .pht files

SYNOPSIS

findmatch file1 file2 [blind=] [diff] [inverse] [list] [mag] [noshift] [radius=%f] [rot] [debug] [list2] [list3] [verbose]

DESCRIPTION

findmatch compares each star in the two .coo or .pht files to find the pairs that are the best matches. A match is considered when the pair is within 2.0 pixels ( or a value set by the radius= switch.) It then computes the shift and (optionally) the rotation angle that will generate the maximum number of matches. If a `-' is used in place of either file1 or file2 then the input is expected from stdin.

FLAGS

blind= increases the match radius for brighter stars in the following manner.

new_radius=radius + (mag-20)*blind_factor

Note: photometry and not coordinate files must be used.

debug gives a lot of printout explaining how the resulting match is made. diff causes the individual row /column differences between the best fitting stars to be printed out. If the mag switch is specified, the magnitude difference is printed out.

inverse modifies the behavior of the list, list2, list3 options in that it prints out only the stars that do not match stars found in file2.

list prints out the lines from file1 that occur in the match instead of the informational line of the number of matches and rotation angle.

list2 prints out the lines from file2 that occur in the match instead of the informational line.

list3 prints out the lines from both file1 and file2 pasted together as a single line that occur in the match instead of the informational line.

mag informs the program that the input files are photometry file and that a magnitude difference between the matching stars should be calculated.

noshift prints out the number of matches that occur without shifting the image.

radius= adjusts the ignore radius from the default value of of 2.0 pixels.

rot turns on the hunt for the best rotation angle. Note: the rotation angle is assumed to be small since the matching is done without a search for rotation. Once the matching stars have been determined, the best shift and rotation angle are calculated.

verbose gives a some extra printout explaining how the resulting match is made. If the list option is not used the program prints out a line like.

nmatch=24 dr=17.748 dc=-10.756 mag_diff=-0.396 angle=.074

the mag_diff will only be printed out if the mag flag is used, the angle will only be printed out if the rot flag is specified.

COORDINATE FILE

For this program a coordinate file is one in which the data are of the format:

star_number row col

Note: The first character of any data line must be a blank, otherwise the line is skipped. In this way header information can be skipped.

BUGS

The blind= switch is a kludge and may be eliminated in the future. The many different switches have very strange interactions. The assumption that the stars have blanks in the first column is very shaky