Background

Procedure

Prerequisites

• DEIMOS software up and running.

Note on illumination

Steps

1. Configure DEIMOS. Using the DEIMOS dashboard:
   • Insert GOH_X (grid of holes) slitmask.
   • Use the TV Guider subpanel to select the desired filter on the TV (note that the TV filter wheel is separate from the dewar filter wheel!).
   • If the telescope is available, open the trapdoor and turn on the dome spec lamps. Otherwise, close the trapdoor and use internal lamps.
2. Launch MAGIQ .
   • Log into k2server via ssh k2obs@k2server
   • Reset DISPLAY as needed to point to the current screen (e.g., open a local xterm, execute command xal, then cut-and-paste this into the k2server window).
   • Launch DCSGUI via dcsgui < /dev/null &
   • Click on DCS > MAGIQ > Current to launch the MAGIQ-K2_Operations menu.
   • Click on MAGIQ-K2_Operations and seelct Start Cam Diagnostic.
   • Wait for MAGIQ - Camera Diagnostic user interface to appear.
3. Configure guider.
   • In the MAGIQ UI, click the Camera droplist and select deimos.
   • Click Connect and confirm thatthe GUI connects properly. If not, try Reconnect. If that fails, try Reset Camera.
   • In the Guider area, set GF Exposure to 300.
   • In the Guider area, set GF Binning to 1.
   • Click expose button to begin exposing. Confirm that exposures start to appear on the display abotu abotu 20 sec.
4. Determine correct integration time.
   • In DEIMOS dashboard, turn on Xe lamp (if using R filter).
   • Check data value in MAGIQ.
   • Adjust exposure time as needed to achieve 5,000-10,000 DN in the vicinity of the "+". As of Nov 2013, it was necessary to use the maximum exposure time (10000 msec).
5. Acquire guider focus loop sequence.
   • In a deimosserver xterm, execute:

     	tvfocloop -wait 2 860 11 20

   • On MAGIQ, select the advanced camera settings tab, enter "22" beside the Save next N Images button, and then click Save next N Images.
   • The script will output a list of focus values and corresponding image names. Save this output for the analysis phase.
6. Turn off guider.
   • In the Guider region, click the Stop button to terminate the exposure sequence.
   • In the Camrea region, click the Camera droplist and select null.
   • Select File > Exit to terminate the GUI.
7. Analyze data.
   • Log into an HQ machine as dmoseng.
   • Go to directory /home/dmoseng/data/focus/tv.
   • Create a file named YYYY-mmm-DD_filter.lst containing the text output by the tvfocloop script (focus values and corresponding image names). See the numerous other sample files in this directory for formatting guidance.
   • Launch the ATV image viewer by entering this command in an xterm window:

     	atv

     When the GUI appears, use the File > Readfits option to read in one of the focus images from the nightly2 directory.
   • Use ATV to measure the (x,y) pixel location of the small spot to the right of the center "plus" sign inscribed into the mirror. As of 2014-Jan-24, the position was (x,y) = (524,638).
   • Run analysis software by typing:

     	~dmoseng/bin/do_analyze_tv_focusloop x y filename

     where filename is the name of a file with the output from tvfocloop and (x,y) are the coordinates of the pinhole in the images. The program will fit a 2D Gaussian to the pinhole images, will display a montage including (from left to right):
     • the original image section
     • the best-fit model
     • the residual
     and will plot the marginal sum in X and Y. Inspect the fist for each image and type Q in the ATV window to proceed to the next. When all images are analyzed the program will derive the best focus, generating a plot and printing a focus value.
   • Add new values to the focus table below.
8. Update default instrument focus. The R-band filter is the fiducial guiding filter and its corresponding focus is the default focus value for the guider. Update the Stow Positions file with the new focus value. Change the line:

   	keylset Stow(TVFOC) srv deimot kwd TVFOCVAL val 930

   inserting the appropriate R-band filter value at the end of the line.

Results

Note that the BVRI filter set is essentially parfocal and thus one should be able to change among these filters without measureable defocus. Whether one should adjust focus when using ND2 and Clear is debatable but perhaps prudent.

Sample Plot