DEIMOS Slitmask Alignment Checklist

Purpose

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
- 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 y2 x2 y2
Complete fine alignment
- 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
- Seelct Spectral readout
- Set exposure time (typically 900-1800 sec)
- Execute wffcs ; goi
- Verify that exposure begins

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.
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 (skypa field on FACSUM)
- Verify pointing origin (shown in lower right corner 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.

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.
- For each alignment box, xbox will plot row and column cuts through the box to show the quality of the centering. Press:
  - q if the centering is acceptable
  - i to ignore the current box if the star is not seen or the object is inappropriate (bad coordinates, galaxy, double-star, etc.)
  - spacebar to reset the sky level if it was incorrectly measured by the program (sky will be reset to the current y-position of the cursor)
- When done reviewing all boxes, xbox will plot a residual map. If any discrepant points are noted, press d to delete the offending point and f to re-do the fit. Press q when the fit is acceptable.
- The program will report the suggested moves in rotation and position, as well as the uncertainties (in parenthesis).
- Answer y to the prompt:
```
     [CONFIRM]  Send DCS commands? (y/n) [y]:
```
- Accept the suggested rotator move if it is significant compared to the uncertainty.
- Perform another alignment iteration if:
  - a rotator move was required, or
  - a move > 0.5 arcsec was required
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 teh 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, you can try this alternative method:

Configure the instrument for imaging:
- select slider 3 and set to zeroth order imaging position, or insert mirror
- set slitmask to None
- set CCD readout mode to Direct
- set exposure time to 20 sec
Acquire first exposure.
Insert the appropriate slitmask.
Acquire second exposure.
Using FIGDISP or IRAF, identify one alignment star on the first image and measure the pixel coordinates. Call these x1 and y1.
On the second image, identify the corresponding alignment box for the alignment star and note the coordinates of the box center. Call these x2 and y2.
Move the telescope by typing the following command into a polo window:
```
	mov x1 y1 x2 y2
```
The alignment stars should now be in their boxes; proceed with fine alignment.