defineobs
defineobs is a GUI application for creating or modifying observation definition files.
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Details:
defineobs constructs or modifies an observation definition file using information input through its gui, or from an image file. If an existing observation definition file is specified in the command line, that file is first opened. The Mask, Dewar Offset File, Grating Order, Grating Angle, and Grism Misalignment boxes take typed input. N&S is an on-off button. The other boxes display drop-down menus when the left mouse button is clicked. The entries should be filled-in or modified from the top down: the choices for Camera depend on the setting for Instrument, and the grating parameters depend on the settings for Camera and Mode. If saving a file with the same name as an existing observation definition file, the existing file filename.obsdef is moved to filename.obsdef% before writing the new file.
Note that the N&S button refers to the direction in which IMACS short camera grisms are mounted, not to whether the exposure is taken in nod and shuffle mode. Disperser Misalignment is an adjustment to the orientation angle of the disperser in the optical model. It can be useful for both IMACS and- particularly- LDSS3 data in correcting for a tilt in the spectrum. If the appropriate value is not known, it can be set to 0; align-mask does a fit for the correct value.
Older versions of observation definition files contained less information than the current version; however, defineobs can handle older files. Missing information is either supplied by the program or the relevant entry in the gui will be blank. All boxes must be filled in before the obsdef file is written. defineobs does more than simply transfer the input information to the file; it uses the date and instrument setup to pick the appropriate dewar and distortion map. Therefore, observation definition files should never be created by hand; always use defineobs.
As an alternative, most of the information required by defineobs may be acquired by specifying a Spectrum File, which is the (unzipped) fits file of an image acquired with the desired set of observation parameters. This can be more convenient and has the advantage that defineobs will use the observation parameters to set the correct default Dewar Offset File for this observing setup. (default dewar offset files are stored in $COSMOS_HOME/sdata/dewoff, and the COSMOS programs will look in this directory for the file if it is not found in the current working directory). Some information, including grism orientation (i.e. if N&S), Grism order, and Grism Misalignment, is not contained in the fits headers and must be entered by hand. Other parameters, such as Dewar Offset File, can be modified as desired. It may be necessary to edit some entries. For example, the mask name may be truncated in the fits file and not match the name of the SMF file.