Synopsis

This checklist describes the procedure for aligning multi-object slitmasks on DEIMOS using the Slitmask Alignment Tool (SAT), a graphical user interface which leads the observers through the entire slitmask alignment process.

Preliminaries

  1. Launch SAT.
  2. Focus telescope.
  3. Configure DEIMOS.

Coarse Alignment

The goal of the Coarse Align phase is to put the alignment stars into their boxes by placing a fiducial star onto a specified guider pixel on the guider.
  1. Select coarse align tab. Click the Guider Coarse Align tab on the SAT.
  2. Select target. Click the Target selector and choose your next target from among the options on the list. The tool will download and display the DSS image corresponding to the DEIMOS guider FOV and will mark the locations of any stars listed in the Guide Star Catalog.
  3. 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:
  4. Grab guider image. Click the Grab Guider Image button, which will:
  5. Select fiducial. Identify the same star in the two guider images:
  6. Move telescope. Click the Move Telescope button to:
  7. Iterate. If the new guider image in the right pane does not have the stars well centered in the red boxes, repeat the preceding steps to re-measure the center and apply another move.

Fine Alignment

In this step, we refine the positions of the stars within their respective alignment boxes to achieve optimal centering of the slitmask.
  1. Select fine align tab. Click the Fine Align tab on the SAT.
  2. Start fine alignment. Click the Start Fine Alignment button. The software will then: It is important not to update the CCD parameters in the Dashboard GUI while the fine alignment is in process. If the CCD parameters are updated in the Dashboard GUI, they will will override the default SAT configuration and the alignment process will fail.
  3. Review fits. Review the object and box fits, calculated offsets, and move recommendations. For each star, the SAT graphs:
    XYFIT codes
    Graphic Description
    white solid line star and box profile
    vertical white dotted line fitted object peak intensity
    green box shows centering of the fitted box
    blue dashed line estimated sky level
  4. Reject bad stars. If necessary, exclude a star from the fit by clicking the corresponding checkbox beside the X/Y cuts. Some possible reasons to remove a star from the fit are: When you exclude a star from the fit, the corrections will be recalculated with that object ignored. Please see the sample image of a star excluded from the fit.
  5. Review moves. If you want to override the default move recommendation, click the Y or N button next to the offset.
  6. Send moves. Note: if observing conditions are variable, it may not be possible to converge below the threshold limits.
  7. In the case the Fine Align procedure does not converge, you can use the alternative Imaging Coarse Align procedure.

Acquire Spectra

  1. 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.
  2. Select Spectral readout. On the Dashboard, change the CCD readout mode to Spectral.
  3. Set exposure time. On the Dashboard, set the exposure time to the appropriate length (typically 900-1800 sec) and enter the desired number of exposures in the entry box to the right of the Expose button.
  4. Click update CCD to set the exposure parameters.
  5. 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.
  6. Verify exposure. Make sure that the exposure begins. It may take a couple of minutes for the FCS to lock.