Summary

This page contains a general description of some of the components of the Slitmask Alignment Tool (SAT) software.


ID Boxes

This panel is used as a sanity check, to ensure that the alignment boxes the sofware detect in the FITS header, propagated from the slitmask database design file, match the actual image of the mask taken with the telescope. This panel is typically used during the afternoon calibrations to preven surprises with bad boxes during the night.


Guider Coarse Align

This panel is used during the first phase of the slitmask alignment procedure at night. The left side of the panel shows a DSS image of the DEIMOS guider field. DSS images are resampled to the guider's pixel scale. Stars recommended for coarse alignment are marked with red squares. Once the telescope is guiding on the field, the command Grab Guider Image allows the observer to take a guider image to compare to the DSS image. In the first iteration of the process, there will typically be some offset between the catalogue star positions (red squares) and the current guider image star positions (white squares). The command Move Telescope will apply the calculated offsets between the guider star positions and the catalogue star positions and re-take a guider image. Typically the coarse alignment is completed within the first iteration.


Fine Align

Once the coarse alignment is completed, the Fine Align panel is used to bring the slitmask alignment within 10-20% of the pixel size. The positions of the alignment boxes are shown in black-background display area to the right of the panel. The set ob back squares on the left side of the panel show the profile of the alignment stars along the X and Y detector axes. The cetroids of these profiles are used to determine the offsets in X, Y and roation between the stars and the alignment box centers.

The following commands are available during fine alignment:


Options panel

This panel is used to modify some of the default options in SAT, such as the exposure time of the alignment images or the automatic check of the mask name. This panel is also used to define if the alignment box information is taken from the FITS headers or from a specific box file, which can be created in the panel ID Boxes.


Actions menu

This panel is used to manually load different images.


Imaging Coarse Align

If for some reason the standard coarse alignment method (comparing the guider image with the corresponding DSS image) does not work, this panel offers the possibility of sending the alignment offsets manually. The procedure consists of taking a DEIMOS image of the science field without the mask in the optical path, followed by another image of the same field with the mask in the optical path. The required offsets to center the alignment stars in the boxes are obtained by manually determining the center of one or several alignment stars and comparing these with the corresponding box centers.