Summary
This page contains a general description of some of the components of the
Slitmask Alignment Tool (SAT) software.
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.
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.
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:
- Start Fine Alignment
- Send Moves and Retake Image
- Send Moves Only
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.
This panel is used to manually load different images.
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.
