Purpose
IMPORTANT NOTE: This procedure is deprecated. Please, use
the Slitmask Alignment Tool
(SAT) checklist to perform the mask alignments.
This checklist describes the procedure for aligning
multiobject slitmasks on DEIMOS, assuming you are:
- using slitmasks which have alignment boxes
- using the xbox software for slitmask alignment
Procedure: Synopsis
This is a brief version for use by experienced DEIMOS observers.
Novices should read the detailed procedure
below.
- Complete preliminary steps
- Focus telescope
- Insert correct slitmask
- Send grating to science wavelength
- Get out finder charts
- Verify target name and coordinates are correct
- Verify position angle
- Verify pointing origin is DEIMOS
- Complete coarse acquisition
- Identify fiducial star on MAGIC display
- Get current coordinates (x1,y1) off MAGIQ
- Get corresponding desired coordinates (x2,y2)
off finder
- Offset telescope with gmov x1 y1 x2 y2
- Complete fine alignment
- Wait for FCS to track
- Click GO ZERO to tilt grating to zeroth order
- Set CCD readout mode to Direct
- Set exposure time to 20 sec
- Click Expose to acquire exposure
- When exposure begins, type do_xbox in IRAF
- When exposure ends, run xbox
- Repeat fine alignment if either:
- A rotation was required
- A move greater than 0.5 arcsec was required
- Acquire science image
- Click GO BACK to tilt grating to science wavelength
- Select Spectral readout
- Set exposure time (typically 900-1800 sec)
- Execute wffcs ; goi
- Verify that exposure starts
Procedure: Detail
Complete preliminary steps
- Focus telescope.
- In the MAGIQ UI, middle click on your next target.
- Ask to OA to run Mira in the neighborhood
of your target. If you'll be on the field for several
hours, then have the OA focus 1-2 hours west of the field.
- Wait about 10 minutes for the OA to acquire an
appropriate star and run Mira.
- Insert correct slitmask. You can do this while the
telescope slews.
- Send grating to science wavelength. Allow the
flexure compensation system (FCS) to correct flexure resulting
from changing the DEIMOS rotator position by setting the
instrument up in your next spectroscopy configuration. Verify
that the flexure compensation system starts sending
corrections (i.e., confirm that the FCS GUI does not indicate
Lockout).
- Get out finder charts. Have it handy for use when
you get to the field.
- Acquire target.
When the OA tells you that your target is on DEIMOS, check
the following information on FACSUM to verify that your
position is correct:
- Verify target name and coordinates are correct
- Verify position angle (Sky PA field
on FACSUM)
- Verify pointing origin (shown in lower left box
of FACSUM)
is DEIMOS
Complete coarse acquisition
The goal of this step is to put the alignment stars into their
boxes by placing a fiducial star onto a specified guider pixel.
- Identify fiducial star. By comparing your finder
chart to the ijmage on the MAGIQ user interface, identify the
fiducial star.
- Get current coordinates. On the MAGIQ UI, place
the cursor on the fiducial star and note the current pixel
location (x1,y1).
- Get desired coordinates. On the finder chart, note
the desired location of this star when the mask is aligned
(x2,y2).
- Offset telescope. At a polo prompt, use
the gmov command to perform a telescope offset from
the current coordinates (x1,y1) to the desired
coordinates (x2,y2):
gmov x1 y1 x2 y2
Note: If you are unable to complete this step, then you may need
to resort to the alternative method of
completing the coarse alignment.
Complete fine alignment
In this step, you will refine the positions of the stars within
their respective alignment boxes to achieve optimal centering of
the slitmask.
- Wait for FCS to track. It's important to allow the
flexure compenstion system to remove any residual flexure
before your acquire your fine alignment images; otherwise, the
xbox software won't be able to locate your
alignment boxes. Wait for the FCSGUI to indicate that the
system is Tracking.
- Click GO ZERO. On the Dashboard's
gratings subpanel, click the
GO ZERO button to tilt the grating to the zeroth
order position for direct imaging.
- Set CCD readout mode to Direct. On the Dashboard,
change the CCD readout mode to Direct.
- Set exposure time to 20 sec. On the Dashboard,
change the exposure time to 20 sec. Note: If
conditions are poor or stars are faint, a longer time may be
required to obtain adequate S/N for centroiding.
- Click Expose. On the Dashboard, click the
Expose to start the exposure.
- Run do_xbox. In the IRAF window, type
do_xbox once the exposure begins. The script will
wait for the current image to be written, will determine the
name of the image, and then will beep to indicate that it's
time for you to wake up and run xbox.
- Run xbox.
Acquire science image
- Click GO BACK. On the Dashboard's
gratings subpanel, click
the GO BACK button to tilt the grating back to
the science wavelength position for spectroscopy.
- Select Spectral readout. On the Dashboard,
change the CCD readout mode to Spectral.
- Set exposure time. On the Dashboard, set the
exposure time to the appropriate length (typically
900-1800 sec).
- Execute wffcs ; goi. Type this
command into a polo xterm window. This will
wait for the FCS to track and then will start a spectral
exposure.
- Verify exposure. Make sure that the exposure
begins. It may take a couple of minutes for the FCS to
lock.
Alternative Coarse Alignment Procedure
If the Easy Way fails to work (for example, predicted TV guider
pixel positions are not available), you can try this alternative
method:
See Also