Quick Review

1. Focus the telescope using MIRA: recomended
2. Acquire the target
3. Coarse Alignment
• Image the target field
• Image the mask: or use images of the mask acquired in the afternoon
• Identify stars
• Offset telescope to comple coarse alignment
4. Fine Alignment:
   • Image the mask: stars are now in the alignment boxes
   • Run check_boxes/lbox for fine alignment
   • Repeat Fine Alignment if necessary.
5. Start Spectroscopic Observations .

Slitmask Alignment

This checklist describes the procedure for aligning multiobject slitmasks on LRIS, assuming there are:

• alignment boxes in the multiobject slitmasks.
• pickoff mirrors for coarse alignment are NOT being used.
• LRIS IRAF routines will be used for alignment.

Focus telescope

Focusing the telescope before aligning a slitmask is recomended. The focus is strongly dependent on the LRIS physical rotator position and, to a lesser extent, the telescope elevation. It is generally recommended to re-focus the telescope when the telescope elevation angle has changed by 30° or more, and/or the instrument's physical rotator position (displayed as drive on the FACSUM display) has changed by 45° or more. In practice, this often means that refocusing is done for each slitmask, since each mask may have a different rotator position.

• Tell the OA the name of your target as listed in your starlist file and also the position angle for the instrument rotator.
• Ask to OA to run MIRA in the neighborhood of your target.
  • If you plan to observe the field for two hours, you may ask the OA to run MIRA one hour ahead of of your target field.
  • MIRA on the blue side should usually be run to focus the telescope because it requires less time to re-configure the instrument.
  • MIRA on the red side should be run only if a good focus is critical to science observations on the red side.

Acquire target

When the OA tells you that your target is on LRIS, check the following information on FACSUM to verify that your position is correct:

• Target name and coordinates
• Position angle (skypa)
• Pointing origin (should be LRIS)

Coarse Alignment

In these steps, we put the stars into the alignment boxes. Either the red or blue beam of the instrument may be used for this step. Most observers choose to use the blue side since it is faster to reconfigure than the red. The following assumes the use of the blue side.

1. Configure the appropriate side of the instrument for imaging:
   • Configure DS9
     • Check that in ds9 Region->File Format -> XY is selected.
     • Check that in ds9 Region->File Coordinate System -> WCS is selected.
   • Set slitmask to direct
   • Set dichroic to any position except clear
   • Set grism to clear
   • Set blue filter appropriately (if you will be taking spectra in the red, use either the clear position or the G filter; using U or B filter could result in problems due to differential atmospheric refraction)
   • Set blue camera focus as appropriate for the selected blue filter.
2. Set exposure time to 10-20 seconds, as desired.
3. Take an image.
4. When image starts reading out,
   • insert the desired slitmask
   • Overlay box coordinates using the ds9 Regions->load regions option. You may have to enter the full path name.
   • Example of boxes overlayed on field and image of the slitmask.

     In this image, it is easy to see the global shift necessary to align stars in boxes.

     This image shows the overlay of the boxes on the image of the slitmask.

5. Identify one alignment star on the image and measure the pixel coordinates in the PANE. Call these x1 and y1.
6. Note the PANE positions of the corresponding box center overlayed on the image. Call these x2 and y2.
7. Move the telescope by issuing a move command.

   Display tool	move command	where
   DS9 blue side	movb x1 y1 x2 y2	lrisserver window
   DS9 red side	moxvr x1 y1 x2 y2	lrisserver window

   
   The alignment stars should now be in their boxes; proceed with fine alignment.

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. Start Guiding:
   Have the OA select a guide star on the movable guider and begin guiding. Ensure that the guide star selected is not too close to the edge of the guider field, since small offsets may still be required.
2. Take an image in 1x1 binning.
3. Start IRAF:
   Select from the desktop menu:
   IRAF and IDL --> IRAF --> cl + ds9
4. load the keck package and the lris subpackage
   While in the IRAF xterminal, load the keck package and the lris subpackage. This should load the routines checkboxes, do_checkboxes lbox, do_lbox, and other routines.
5. cd to the data directory.
   • If you do not know the data directory, type "s outdir" in a lrisserver window.
     outdir = /sdata240/lris1/2000feb07 (unix path name)
   • In the iraf terminal type:
     cd /s/sdata240/lris1/2000feb07
     The "/s" is required to access a summit directory from headquarters.
6. Run do_lbox or optionally do_check_boxes
   • do_lbox
     • waits for the image to complete writing to disk
     • launches lbox
   • do_check_boxes
     • waits for the image to complete writing to disk
     • displays the image
     • reads and overlays box positions on image
     • allows observers to adjust and move box positions
     • launches lbox
7. Repeat steps 2 and 6 if necessary.
   Until the translation and rotation are within your tolerances, repeat steps 2 and 6. Typically, a mask is aligned when the translation and rotation are within the measurement errors given in parenthesis.
   • The lbox routine will report suggested moves in rotation and position, as well as the uncertainties (in parenthesis).
   • Perform another alignment iteration if:
     • a rotator move was required
     • either the north or east offset was > 0.2 arcsec (or whatever your personal tolerance is!)

Spectroscopy

• Reconfigure the instrument for spectroscopy:
  • Set dichroic and gyrism to the appropriate position for spectroscopy
  • Set blue filter to clear position
  • Set blue camera focus as appropriate for the clear position.
• Set exposure time as desired for spectroscopy.
• Expose...phew!