Quick Review

  1. Launch the SAT
  2. Load the starlist
  3. Retrieve DSS images of guider fields in the afternoon
  4. Focus the telescope using MIRA if needed
  5. Slew to target and, while slewing, configure MOSFIRE to image the alignment slitmask
  6. Complete Coarse Alignment :
  7. Complete Fine Alignment:
  8. Start spectroscopic observations

The Tips and Tricks section covers topics such as alignment of crowded fields, alignment check for targets requiring very long (more than 2 hours) integrations and manually loading old alignment images.

Slitmask Alignment

This checklist describes the procedure for aligning multi-object slitmasks on MOSFIRE using the Slitmask Alignment Tool (SAT). Released for use in June 2012 during MOSFIRE commissioning, the SAT provides a complete set of tools for aligning slitmasks. Given a properly-formatted starlist, the SAT predicts guide star locations which may be used to coarse-align a slitmask. When fine-tuning mask alignment, the SAT displays graphical fits to objects/boxes in an all-in-one display and makes recommendations for telescope offsets and rotation. Mask alignment with the SAT is more efficient than the traditional command-line and IRAF-based scripts.

Launch the SAT

To launch the SAT:

  1. Navigate to an “analysis” VNC desktop (blue background)
  2. From the window manager background menu select MOSFIRE Utilities -> Slitmask Alignment Tool

Load the starlist

Click on the "Load Star List" button immediately below the left-hand image the SAT.

WARNING! The target coordinates in the starlist must correspond to the center of the mask, accounting for all relative shifts that may have been applied while designing the masks. To ensure that the proper coordinates are entered into your starlist file, generate your starlist using our custom script for MOSFIRE.

Focus Telescope (Optional)

Focusing the telescope before aligning a slitmask should be done periodically during the night but is not necessary to do before every mask alignment. We generally recommended re-focusing the telescope when the telescope elevation angle has changed by 30° or more since the previous focus.

To complete the focus:

  1. Select target on MAGIQ. On the MAGIQ Observer UI, locate the line listing your next target in the target list at the bottom of the window. (Note: this can be done while you have an exposure in progress) Click the middle mouse button on that line to highlight it, thus indicating to the OA which target you plan to observe.
  2. Select focus star. Ask the OA to locate a suitable star to run MIRA in the neighborhood of your next target. The process can take the OA several minutes.
  3. Queue align mask. Pre-configure the CSU for your alignment. On the MAGMA UI, click on the name of the next mask to observe in the Mask Configurations area, then click on Setup Alignment Mask to queue the moves in the controller. (Note: this can also be done while the exposure is in progress)
  4. Wait for exposure. Wait for your current exposure to complete.
  5. Protect detector. On the MOSFIRE Desktop Observing Mode UI, click on DARK-IMAG mode to protect the detector from exposure to bright light during your reconfiguration and telescope slew.
  6. Slew to focus star. Ask the OA to slew the telescope to the focus star and run MIRA in the neighborhood of your new target.
  7. Confirm safe drive angle. Check the drive angle shown on FACSUM. If it is within ±10° of either 0° or 180° (or any multiple of 180°) then moving the CSU may trigger a CSU fatal error. To avoid this, have the OA rotate MOSFIRE to a safe drive angle and execute your CSU move at that rotator position.
  8. Execute CSU move. On the MAGMA UI, click on Execute Mask to perform the moves you queued above.
  9. Wait for mask. Be sure to tell the OA to wait until your CSU move is completed before launching the telescope focus routine (MIRA).
  10. Launch MIRA. Once the mask move is done, ask the OA to complete MIRA. Wait while the OA completes the focus routine.

Notes

Prepare for Alignment

In this phase, we prepare the instrument for mask alignment during the telescope slew to the science field.
  1. Click Quick Dark on the MOSFIRE Desktop Observing Mode GUI.
  2. Setup Alignment Mask
  3. Wait for Filter to move to the Dark
  4. Confirm safe drive angle.
  5. Execute Mask.
  6. Optional: Click Dark Imaging: J . This configures the spectrograph efficiently for J-band imaging, which is the filter used for imaging the mask.
  7. Load coarse align. Click the Coarse Align tab on the SAT.
  8. Verify pointing. When the OA tells you that your target is on MOSFIRE, check the following information on FACSUM to verify that your position is correct:

Coarse Alignment

In this phase, we put the stars into the alignment boxes using the SAT Guider Coarse Align tab.

  1. Select target. Click the target list selector on the SAT Guider Coarse Align tab and select the target to observe. By default, this drop-list displays Current DSS, but you should select the desired target to trigger SAT to verify your pointing. This will:
  2. Wait for OA to turn Guiding on
  3. Grab guider image. Click the Grab Guider Image button once the telescope is in position. This will: Observers may adjust the brightness and contrast (if necessary) by right-clicking on the image and dragging the mouse.
  4. Click On Star in Guider image on the right hand side Select an object which is visible in both the predicted DSS guider image at left and the actual guider image at right. The SAT will then: If the SAT highlights the incorrect star in the DSS image, select a different star either by clicking in the DSS image or selecting the star in the guide star table.
  5. Click Move Telescope. This will cause SAT to:
  6. Verify move. Wait for the guider image on SAT to update and verify that the stars are in the RED boxes on the right-hand side guider image now agree. If necessary, click on a new star and send another telescope move to improve the centering.

Fine Alignment

In this phase, we refine the positions of the stars within their respective alignment boxes to achieve optimal centering of the slitmask using the SAT Fine Align tab.

  1. Check that the CSU has finished moving. Wait for the CSU to finish the alignment mask configuration.
  2. Optional: Verify the exposure options. The instrument configuration options set on the SAT Options tab are appropriate. Unless set to current, these override the current instrument settings.
  3. Click Start Fine Alignment button on SAT to start the fine alignment process. The software will then:
  4. Review fits. For each star the SAT graphs: Review the object and box fits, calculated offsets, and move recommendations.
    XYFIT codes
    Graphic Description
    White solid line Star profile (sky subtracted)
    White dotted vertical line Star center
    Red solid vertical line Predicted star position
    Green box Shows centering of the fitted box
    Yellow dashed line Box profile (object +sky)
  5. Remove outliers. If necessary, exclude a star from the fit by clicking the button to the left of the offending star's graphs. Possible reasons to remove a star from the fit are: If you exclude a star from the fit, SAT will recalculate the moves ignoring that object. Please see the example image showing a star excluded from the fit.
  6. Review moves. In the Offsets area, the SAT displays the recommended moves in X, Y, and rotation. Moves which are significant are enabled by default, while small moves are disabled. If you want to override the default move recommendation, click the Y or N button next to the offset.
  7. Send moves.

Spectroscopy

Reconfigure MOSFIRE for spectroscopy:
  1. Click Setup Science Mask:

    On MAGMA, click Setup Science Mask to prepare the CSU for moving the alignment bars to the science position.

  2. Click Quick Dark mode:

    On the MOSFIRE desktop Observing Mode GUI, select Quick Dark mode (to prevent persistence)

  3. Wait for filter. Filter should say DARK. The graing may continue to move.
  4. click EXECUTE Mask:

    On MAGMA, click Execute Science Mask to prepare the CSU for moving

  5. Click on the desired Dark spectroscopic mode:(e.g. H )

    On the MOSFIRE desktop Observing Mode GUI, select Dark Spectroscopy: band (e.g. H) for the spectroscopic mode for your science. This efficiently configures the filter, grating, and pupil for your science setup.

  6. Configure detector.

    On the MOSFIRE desktop Exposure Control GUI, set the exposure and nod parameters:

  7. Wait for CSU mask.

    Wait for the CSU move to complete the move.

  8. Set grating/filter.

    On the MOSFIRE desktop Observing Mode GUI, select the appropriate spectroscopy mode.

  9. Start exposure.

    On the MOSFIRE desktop Exposure Control GUI, click on Wait & Go button to begin the exposure.

Phew!

Appendices

Retrieve all Guider Images

Do this step in the afternoon to save time at night:
  1. Click the Coarse Alignment tab on the SAT.
  2. If you have not already loaded the starlist, click Load Star List, locate the appropriate directory, and select the appropriate starlist file.
  3. Click, Retrieve all Guider Images. This will store FITS images in the data directory for each target in the list. The FITS data will have names target.fits
  4. To preview the guider fields, select a target in the target dropdown list. By default the list shows Current DSS as the target.
Note: If you modify the coordinates in your target list, you will need to re-click on Retrieve all Guider Images to update your guider images.

Tips and Tricks

To specify the sky frame to use for background subtraction

  1. Select Actions -> Load MOSFIRE Sky Image
  2. Set all moves to N
  3. Click Send Moves and Retake Image to trigger a new image at the current position. It will use the selected sky image as the sky.

To load an alignment image manually

  1. Click Actions -> Load Fine Alignment Image.
  2. If necessary, use the Actions -> Load MOSFIRE Sky Image to set the sky image to match.

Alignment check

When observations require very long integrations it is recommendable to perform an alignment check every 2 to 2.5 hours to make sure targets are still well centered in the slits. This can be done easily and efficiently with the option Check Alignment in SAT's Fine Alignment tab. The procedure to perform an alignment check is as follows:

Crowded Field Fine Alignment

For some fields it may be necessary to use guile to fine align a slitmask due to the density of objects in the field. Below are some tips and tricks that may be used to manipulate the software and align a mask.