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CORRECTING THE MECHANICAL POSITIONING OF THE WHEELS

From time to time the position and tilt of the slit, grism and pupil wheels should be measured more precisely, especially when mechanical interventions in the entrance wheel have taken place.

WARNING: the following procedures are relatively risky. Feel encouraged to seek help from engineers or instrument specialist.

Correcting the mechanical positioning of the slit wheel

In case the slit is tilted with respect to the detector columns the wheel has to be rotated until properly aligned using EPICS.
  1. Check that the telescope is pointing to zenith.

  2. Check that the primary mirror petals are open.

  3. Check that the tertiary mirror is out (i.e. light to CASS focus), specially after a GLAS run.

  4. Switch on the weak dome flat lamp (at full intensity):

    SYS> fflamp 1 on

  5. Check that the agmirror is out. If not:

    SYS> agmirror out

  6. Take an image of the problematic slit (l0p75 in this example):

    SYS> limage hc

    SYS> lslit l0p75

    SYS> glance liris 3

  7. If there is some misalignment, then start EPICS (WARNING: the following procedure is relatively risky. Feel encouraged to seek the help from engineers or instrument specialist):

    SYS> start_epics

    In the EPICS window, clic on "LIRIS" (at the ENGINEERING column), then clic on "SLIT", then clic on " MOTOR". From the last window that shows up, write down the current VAL value (your VALinitial) .

  8. Introduce some small value (~0.05) in the box next to TWV, press return and then click on TWF (to move the slit wheel down) or TWR (to move the slit wheel up). The 'slit wheel' moves as shown by the 'entrance wheel' in this diagram. Then:

    SYS> glance liris 3

    and iterate until you get a good alignment. Then write down the new VAL value (your VALfinal).

    The VARIATION ANGLE (same as the 'distance' value that will be requested in step 11) is the result of the final VAL minus the initial VAL (distance=VALfinal-VALinitial).

  9. Make and cd into a new directory following the date, such as:

    SYS> mkdir /home/whtobs/liris/slits20080610

    SYS> cd /home/whtobs/liris/slits20080610

  10. Get the present position of the slit wheel:

    SYS> lbuild_mch_hometables lslit_config.dat lslit_distance.dat -home1 lslit_home1.dat.old -home2 lslit_home2.dat.old -dir /wht/etc/

  11. Modify it with the new values (in the directory you just created)

    The following will ask you the position to change (0=quit): Look at taurus:/wht/var/lslit_home1.dat to check which line number corresponds to the problematic slit. The line number will be the position to change.

    SYS> lbuild_mch_hometables lslit_config.dat lslit_distance.dat -home1 lslit_home1.dat -home2 lslit_home2.dat -distf lslit_distance.dat -chpos -dir /wht/etc/

    Now it will ask you to introduce the variation angle (distance); type the value you previously calculated (the result of VALfinal-VALinitial).

    Finally, type 0 to quit the script.

    NOTE: The described procedure affects ONLY the slit at position. If you want to change the position of the home mark (therefore changing EVERY slit by the same amount), type -1 when asked about the position to change (0=quit).

  12. Now, copy the files to where they belong and load the new configuration:

    SYS> cp lslit_home1.dat /wht/var/

    SYS> cp lslit_home2.dat /wht/var/

    SYS> lloadconfig slit

    Log in to taurus as lirissm (you will need the password):

    SYS> ssh taurus -l lirissm

    Set the current directory:

    SYS> cd /wht/etc/liris

    Rename the old file:

    SYS> mv lslit_distance.dat lslit_distance_pre_yyyymmdd.dat

    Copy new version:

    SYS> cp /home/whtobs/liris/slitsyyyymmdd/lslit_distance.dat .

    Once finished, exit from the lirissm account:

    SYS> exit

  13. To be sure the file is loaded correctly reboot the LIRIS IOC VME crate (located on the telescope) by pressing the red reset button on the CPU card inside the VME. After that, in the ICS screen give the commands:

    SYS> lsethome all

    NOTE: It will take more than 10 minutes to set the wheels at home position.

    SYS> lcamera camerain

  14. Once you have finished close the EPICS windows by clicking on the cross at the top right corner of each window.



Correcting the mechanical positioning of the grism wheel

In case the spectra are tilted with respect to the detector columns the grism wheel has to be rotated until alignment using EPICS.
  1. Check that the telescope is pointing to zenith.

  2. Check that the primary mirror petals are close.

  3. Check that the tertiary mirror is out (i.e. light to CASS focus), specially after a GLAS run.

  4. Turn the arc lamps on (Ar or Xe):

    SYS> llampon 1

  5. Check that the agmirror is in. If not:

    SYS> agcomp

  6. Take an arc with the problematic grism (lr_zj in this example):

    SYS> lspec lr_zj l0p75

    SYS> glance liris 3

  7. If there is some misalignment, then start EPICS (WARNING: the following procedure is relatively risky. Feel encouraged to seek the help from engineers or instrument specialist):

    SYS> start_epics

    In the EPICS window, clic on "LIRIS" (at the ENGINEERING column) , then clic on "GRISM", then clic on " MOTOR". From the last window that shows up, write down the current VAL value (your VALinitial).

  8. Introduce some small value (~0.05) in the box next to TWV, press return and then click on TWF or TWR (check this diagram for directions). Then:

    SYS> glance liris 3

    and iterate until you get a good alignment. Then write down the new VAL value (your VALfinal).

    The VARIATION VALUE will be the new VAL minus the initial VAL (VALfinal-VALinitial).

  9. Make an cd into a new directory following the date, such as:

    SYS> mkdir /home/whtobs/liris/grisms20080610

    SYS> cd /home/whtobs/liris/grisms20080610

  10. Get the present position of the grism wheels:

    SYS> lbuild_mch_hometables lgrism_config.dat lgrism_distance.dat -home1 lgrism_home1.dat.old -home2 lgrism_home2.dat.old -dir /wht/etc/

  11. Modify it with the new values (in the working directory)

    The following will ask you the position to change (0=quit). Look at taurus:/wht/var/lgrism_home1.dat to check which line number corresponds to the problematic grism. The line number will be the position to change.

    SYS> lbuild_mch_hometables lgrism_config.dat lgrism_distance.dat -home1 lgrism_home1.dat -home2 lgrism_home2.dat -distf lgrism_distance.dat -chpos -dir /wht/etc/

    Now it will ask you to introduce the variation value (distance). Type the VAL you previously calculated (the result of VALfinal-VALinitial).

    Finally, type 0 to quit the script.

    NOTE: The described procedure affects ONLY the grism at position. If you want to change the position of the home mark (therefore changing EVERY grism by the same amount), type -1 when asked about the position to change (0=quit).

  12. Now, copy the files to where they belong and load the new configuration:

    SYS> cp lgrism_home1.dat /wht/var/

    SYS> cp lgrism_home2.dat /wht/var/

    SYS> lloadconfig grism

    Log in to taurus as lirissm (you will need the password):

    SYS> ssh taurus -l lirissm

    Set the current directory:

    SYS> cd /wht/etc/liris

    Rename the old file:

    SYS> mv lgrism_distance.dat lgrism_distance_pre_yyyymmdd.dat

    Copy new version:

    SYS> cp /home/whtobs/liris/grismsyyyymmdd/lgrism_distance.dat .

    13. Once finished, exit from the lirissm account:

    SYS> exit

  13. To be sure the file is loaded correctly reboot the LIRIS IOC VME crate (located on the telescope) by pressing the red reset button on the CPU card inside the VME. After that, in the ICS screen give the commands:

    SYS> lsethome all

    NOTE: It will take more than 10 minutes to set the wheels at home position.

    SYS> lcamera camerain

  14. Once you have finished close the EPICS windows by clicking on the cross at the top right corner of each window.



Correcting the mechanical positioning of the pupil wheel

From time to time, the alignment of every pupil stop should be checked.
  1. Check that the telescope is pointing to zenith.

  2. Check that the primary mirror petals are open.

  3. Check that the tertiary mirror is out (i.e. light to CASS focus), specially after a GLAS run.

  4. Switch on the weak dome flat lamp; set it at 50% intensity:

    SYS> fflamp 1 on

    SYS> fflampspwm 50

  5. Set the camera to reimaging mode in h filter and pupil for ks band (in this example):

    SYS> limage h

    SYS> lcamera reimaging

    SYS> lpupil pcblnkxl

  6. Check that the agmirror is out. If not:

    SYS> agmirror out

  7. Take an image:

    SYS> run liris 1 "pupil"

  8. Take a look at the image. You should see an image (like this one) of the primary mirror+the shadow of both the secondary and its spider+the shadow of the K pupil (a round spot in the centre plus 3 legs).

    • If it is well centered (that is, if the pupil is correctly masking the shadow of the secondary mirror), then you only need to set back the observing mode by doing:

      SYS> lcamera camerain

      • and the check finishes here.

    • If there is some misalignment, then you need to proceed as described in the following steps.

  9. Start EPICS (WARNING: the following procedure is relatively risky. Feel encouraged to seek the help from engineers or instrument specialist):

    SYS> start_epics

    In the EPICS window, clic on "LIRIS" (at the ENGINEERING column), then clic on "PUPIL", then clic on "MOTOR". From the last window that shows up, write down the current VAL value (your VALinitial).

  10. Introduce some small value (~0.05) in the box next to TWV, press return and then click on TWF or TWR (check this diagram see the direction). Then reimage the pupil:

    SYS> glance liris 1

    and iterate until you get a good alignment. Then write down the new VAL value (your VALfinal).

    The VARIATION VALUE or distance will be the new VAL minus the initial VAL (VALfinal-VALinitial).

  11. Make and cd into a new directory following the date, such as:

    SYS> mkdir /home/whtobs/liris/pupils20080610

    SYS> cd /home/whtobs/liris/pupils20080610

  12. Get the present position of the pupil wheels:

    SYS> lbuild_mch_hometables lpupil_config.dat lpupil_distance.dat -home1 lpupil_home1.dat.old -home2 lpupil_home2.dat.old -dir /wht/etc/

  13. Modify it with the new values (in the working directory)

    The following will ask you the position to change (0=quit): Look at taurus:/wht/var/lpupil_home1.dat to check which line number corresponds to the problematic pupil. The line number will be the position to change.

    SYS> lbuild_mch_hometables lpupil_config.dat lpupil_distance.dat -home1 lpupil_home1.dat -home2 lpupil_home2.dat -distf lpupil_distance.dat -chpos -dir /wht/etc/

    Now it will ask you to introduce the variation value: Type the VAL you previously calculated (the result of VALfinal-VALinitial).

    Finally, type 0 to quit the script.

    NOTE: The described procedure affects ONLY the pupil at position. If you want to change the position of the home mark (therefore changing EVERY pupil by the same amount), type -1 when asked about the position to change (0=quit).

  14. Now, copy the files to where they belong and load the new configuration:

    SYS> cp lpupil_home1.dat /wht/var/

    SYS> cp lpupil_home2.dat /wht/var/

    SYS> lloadconfig pupil

    Log in to taurus as lirissm (you will need the password):

    SYS> ssh taurus -l lirissm

    Set the current directory:

    SYS> cd /wht/etc/liris

    Rename the old file:

    SYS> mv lpupil_distance.dat lpupil_distance_pre_yyyymmdd.dat

    Copy new version:

    SYS> cp /home/whtobs/liris/pupilsyyyymmdd/lpupil_distance.dat .

  15. Once finished, exit from the lirissm account:

    SYS> exit

  16. Now, keep on checking the other pupils, such as e.g. pcblnk:

    SYS> lpupil pcblnk

    image it and repeat the procedure above.

  17. After finishing this procedure with all the pupils, to be sure that the files were loaded correctly, reboot the LIRIS IOC VME crate (located on the telescope) by pressing the red reset button on the CPU card inside the VME. After that, in the ICS screen give the commands:

    SYS> lsethome all

    NOTE: It will take more than 10 minutes to set the wheels at home position.

    SYS> lcamera camerain

  18. Once you have finished close the EPICS windows by clicking on the cross at the top right corner of each window.


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Contact:  (LIRIS Instrument Specialist)
Last modified: 06 October 2015