The CHARA Array Wiki

Coude alignments help keep the blue beacon from drifting during slews. Needed when drift is excessive and makes realigning difficult when on sky.

1. Start with an M10 alignment before beginning the coude process (usually done on POP 5)
2. Send M7's to default
3. Do regular beginning of the night alignment procedure
   1. align beacon, dichroic, focus labao, focus wfs
4. Open an engineering hut GUI: » hutgtk -E S1 &
   1. AOB ENG tab
   2. note the M7_1 and M7_2 actuator positions and enter them on the Excel page.
      1. Select and hit [GET].
      2. Value reads below get and should match last entry on excel
5. Turn powers on and enable scope(s)
6. Dome GUI, Auto tab:
   1. On 'Az Pos', enter the stow position + 180
   2. [Set Pos]
7. Watch beacon spots and use M7 to keep them centered while it rotates 180°.
8. Obsgtk, align M7 when it stops moving.
9. Hut GUI, note new M7_1 and M_2 values and enter in excel.
   1. ignore last 3 digits and record first 4
   2. spreadsheet will calculate the average value
   3. enter the average value + 3 zeros for each actuator (M7_1 and M7_2).
   4. If its a large move, watch the beacon spots as they move away because you will need to recenter them
10. Use the dichroic to realign the beacon to labao
11. Hit [STOW] to return to stow position
12. The beacon movement should be much smaller returning to stow than it was going away from stow
13. Align M7
14. Enter new actuator positions into excel
15. Hut GUI, send both actuators to calculated position.
16. Align dichroic
17. if the beacon movements were small on the way back to stow, then the coude alignment is finished. If it wasn't, repeat until it is.
18. Hut GUI, save the new M7 dichroic positions by hitting [DICHR POS] then [WRITE CFG]
    1. it will save them to /ctrscrut/chara/etc/S1_aob.cfg
19. Can enter any notes on why coude alignment was needed on excel sheet.

Make sure the vacuum is below 5 torr in the pipe.

• Proceed with the usual steps up to LAB DICH alignment with labao.
• Adjust by hand DM tilt to front side of front rail target
• Cart at the back. Adjust BRT using brtgtk to back side of front rail target.
• Use Obsgtk to send M7 to default position. (this is just in case, it did not go there at the end of night)
• Do M10 alignment. Close laser shutter. (Dome shutter has to be closed daytime, and dome light off, spycam off [switch to M10 TV] )
• Set laser to ND=4 (laser shutter closed)
• Switch on ACQ camera, watch the bright beacon spot and move it to the hole
• Align beacon to twfs (laser shutter closed)
• (open M5 cover) Find beacon on labwfs, if not seen, open laser shutter and watch the laser spots appearing in ACQ TV.
• use the SCOPE DICH buttons: UP, DOWN, LEFT or RIGHT to overlap laser spots with the closest beacon spots
• Align SCOPE DICH to labwfs.
• Adjust Beacon focus to labwfs: hit BEAC FOC in labao gui. After that adjust focus to twfs: hit FOCUS WFS in twfs gui.

Now you are set for labwfs Coude, but for the scopes with original M7 cones it is better to start with an Acquisition Coude instead of labwfs Coude.

As of 6/1/2021 only E2 has the new cones.

• Close the Beacon Flat cover, and Fiber cover on AOB
• For the scopes with DMs (S2,W1,S1?), use the (POWER ON) button on the WFS GUI (WFS/AO tab) to power the DM on. Make sure that the DM current and temperature are displaying numbers. Press LAST FLAT to make sure that the last sky flat is loaded. If for some reason that flat is not good, go back to DEF FLAT.
• Open M3 cover and send the corner cube IN. Laser at ND=4 (or 2.3) Open laser shutter.
• One laser spot should be in the hole. Select the brightest laser spot that is not in the hole, use the ACQ GUI to zoom in at least one level to that spot. Adjust zoom window UP, DOWN, LEFT or RIGHT to roughly center that spot in the window.
• Use the ACQ GUI buttons to move the cross hair to the selected laser spot, and write down the coordinates of the crosshair as displayed in the ACQ GUI next to “Origin”.
• Turn on the power to the drives for AZ and EL and use the telescope GUI to rotate the telescope by 180º in azimuth with respect to the stow position.
• Turn on the power to the drives for AZ and EL and use the telescope GUI to rotate the telescope by 180º in azimuth with respect to the stow position.
• When it reaches the new position, move the cross hair to the new position of the laser spot and write down the new coordinates.
• Calculate the coordinates of center position of the two points and move the crosshair to this central position. This is the target position of the laser spot.
• Open an engineering hut gui by typing hutgtk -E [telescope] in a terminal window. In the AOB ENG tab, find the M7_1 and M7_2 entries in the pull down menu next to the [ 100 ] displayed in the white field at the lower left. Select each one and hit the GET button to display the position of the M7 mirror actuators. The values are ideally around 3000000, but can range from 1000000 to 5000000. Write down the value of each actuator as a reference before making any adjustments.
• Using the yellow M7 buttons, move the mirror UP, DOWN, LEFT or RIGHT to center the spot on the crosshair. The actuators may reach a limit if they are moved too far when trying to make a large correction. Be more cautious if the starting value is already close to one of the limits (get help for manual adjustment if necessary). The limits are 0 on one end and around 6000000 on the other limit. Once the laser spot has reached the crosshair, write down the new actuator positions for M7_1 and M7_2 on the sheet.

• Close the laser shutter
• On AOB open Bflat and Fiber covers, turn on red and blue beacons.
• Align beacon to twfs
• Align SCOPE DICH to labwfs, if beacon spots are not in the boxes start with using the SCOPE DICH buttons: UP, DOWN, LEFT or RIGHT to center the spots in the boxes.
• Type “coude” in the labao server to start the automated coude alignment. This will send the telescope back to STOW.
• In the end, if the target coordinates are acceptable, let the M7 actuators move to the target positions.
• Align beacon to twfs (should be very little adjustment)
• Align SCOPE DICH to labwfs, if beacon spots are not in the boxes start with using the SCOPE DICH buttons: UP, DOWN, LEFT or RIGHT to center the spots in the boxes.
• Adjust Beacon focus to labwfs: hit BEAC FOC in labao gui. After that adjust focus to twfs: hit FOCUS WFS in twfs gui.
• Go to the AOB ENG tab on the hut engineering gui and save the new default M7 position by hitting the “DICHROIC POSITION” (or similar) button, and then “SAVE ..(stg)”. [<this button is in the same row as the DICHROIC POSITION button.] A new configuration file is now saved, that also includes the tilts of beacon flat, AOB splitter, and focuses.

• 2021Jun01 - Document written by Judit Sturmann.
• 2021Jun02 - Gail Schaefer added to wiki page.
• 2021Jun02 - Removed link for old Coude Alignments (googledoc in 2019).
• 2021Jun02 - Remove link for old Azimuth Coude Alignments (wiki page created in 2018).