apmask: Create and IRAF pixel list mask of the apertures

Package: echelle

Usage

apfind input

Parameters

input: List of input images with aperture definitions.

output: List of output mask names. As a convention the extension ".pl" (pixel list) should be used.

apertures = "": Apertures to recenter, resize, trace, and create a mask. This only applies to apertures read from the input or reference database. Any new apertures defined with the automatic finding algorithm or interactively are always selected. The syntax is a list comma separated ranges where a range can be a single aperture number, a hyphen separated range of aperture numbers, or a range with a step specified by "x<step>"; for example, "1,3-5,9-12x2".

references = "": List of reference images to be used to define apertures for the input images. When a reference image is given it supersedes apertures previously defined for the input image. The list may be null, "", or any number of images less than or equal to the list of input images. There are three special words which may be used in place of an image name. The word "last" refers to the last set of apertures written to the database. The word "OLD" requires that an entry exist and the word "NEW" requires that the entry not exist for each input image.

interactive = no: Run this task interactively? If the task is not run interactively then all user queries are suppressed and interactive aperture editing is disabled.

find = yes: Find the spectra and define apertures automatically? In order for spectra to be found automatically there must be no apertures for the input image or reference image defined in the database and the parameter nfind must be greater than zero.

recenter = no: Recenter the apertures?

resize = no: Resize the apertures?

edit = yes: Edit the apertures? The interactive parameter must also be yes.

trace = yes: Trace apertures?

fittrace = yes: Fit the traced points interactively? The interactive parameter must also be yes.

mask = yes: Create mask images?

line = INDEF: The dispersion line (line or column perpendicular to the dispersion axis) to be used in finding, recentering, resizing, editing, and starting to trace spectra. A value of INDEF selects the middle of the image.

nsum = 1: Number of dispersion lines to be summed or medianed. The lines are taken around the specified dispersion line. A positive value takes the sum and a negative value selects a median.

buffer = 0.: Buffer to add to aperture limits. One use for this is to increase the width of the apertures when a mask is used to fit data between the apertures.

Additional parameters

I/O parameters and the default dispersion axis are taken from the package parameters, the default aperture parameters from apdefault, automatic aperture finding parameters from apfind, recentering parameters from aprecenter, resizing parameters from apresize, parameters used for centering and editing the apertures from apedit, and tracing parameters from aptrace.

Description

Pixel list masks are created from the aperture definitions in the input images. Pixel list masks are a compact way to define arbitrary regions of an image. The masks may be used directly as an image with values of 1 (in an aperture) and 0 (outside an aperture). Alternatively, some tasks may use a mask to define regions to be operated upon. When this task was written there were no such tasks though eventually some tasks will be converted to use this general format. The intent of making an aperture mask is to someday allow using it with the task imsurfit to fit a background or scattered light surface. (See apscatter for an alternative method).

Examples

1. To replace all data outside the apertures by zero:

cl> apmask image image.pl nfind=10
cl> imarith image * image.pl image1

Revisions

APMASK V2.11: The "apertures" parameter can be used to select apertures for resizing, recentering, tracing, and extraction. This parameter name was previously used for selecting apertures in the recentering algorithm. The new parameter name for this is now "aprecenter".