NAME

findsky -- determine the sky levels at each band of an image cube

USAGE

findsky cube_image coord_file

PARAMETERS

cube_image

the name of the 3D image cube to be measured

coord_file

the name of the text file containing pairs of (x y) coordinates at which the sky level is to be estimated

navgx = 3

the number of columns to average when determining the sky

navgy = 3

the number of rows to average when determining the sky

sky =

a user variable to override the calculated sky value for a given image band

okay =

an interactive reply variable

verbose = yes

if set to yes, the user is allowed to review and override the derived sky values

DESCRIPTION

The pixels at and surrounding the coordinates contained in the file given by "coord_file" are averaged over "navgx" and "navgy" to determine the mean for the sky at that location. When several coordinate pairs are present, the values are averaged and a standard deviation is computed. The calculations are performed for each band in the image cube. Resulting values are displayed on the terminal, and optionally may be altered by the user.

Final values for the sky estimate are stored in the image header as keywords SKYNN, where NN may be 01 through the number of image bands in the cube, typically less than 25.

EXAMPLES

Read the coordinate file sky.cor, and measure the sky values.

cl> findsky cube sky.cor navgx=5 navgy=5

The 25 pixels surrounding each coordinate pair are averaged at each band in the cube.

TIME REQUIREMENTS

Less than 1 second per band.

SEE ALSO

VELOCITY