SEEING

Name

seeing

Purpose (one Line Only)

Given an astronomical image, determine the image quality (seeing).

Description

Calling Sequence

seeing,image,fwhm,objrad,nstars

Inputs

image - Array containing image to be examined.

Optional Input Parameters

Keyword Input Parameters

FWHMGUESS - Initial guess of the FWHM in the image. Default=3. If this
is significantly smaller than the actual seeing you will
get an answer that is much too small. The penalty for
guessing a larger than optimal value appears to be weak.
MINSIGNAL - minimum signal to consider when looking for sources
(default=0)
MAXSIGNAL - maximum signal to conisder when looking for sources
(default=60000)
NODISPLAY - Flag, if set will suppress plot and image outputs
RADP - Flag, if set uses a radial profile gaussian fit to determine
the FWHM. This is more accurate if the seeing is gaussian
and well behaved. This option will be slower and slightly
more prone to failure, particularly for faint sources.

Outputs

fwhm - Image quality, FWHM in pixels for the image.
objrad - Object aperture radius used to determine fwhm
nstars - Number of stars that were averaged to get fwhm

Keyword Output Parameters

ERROR - set to 1 (true) if an error occurred, zero otherwise. If the
error flag is set, the return values may or may not be useful.

Common Blocks

Side Effects

Restrictions

Procedure

Modification History

Written by Marc W. Buie, Lowell Observatory, 2004/07/03
2005/06/28, MWB, added extra error trapping and ERROR keyword
2008/07/23, MWB, added keyword for initial FWHM guess
2013/07/06, MWB, added RADP keyword option
2016/06/24, MWB, added some extra optional plot output