Text Size:
Smaller Text Normal Text Larger Text


HiRAC filter Setup Procedures

Comments to Lars Freyhammer

Table Of Contents:

Installation of filters

The following procedure is used when inserting filters in HiRAC.
  1. Find the filters to be installed in the filter merry-go-round. Please update whiteboard filter overview.
  2. If the filters are not mounted in HiRAC filter holders, get the round holders from the HiRAC filter holders box and lock rings from the HiRAC rings box.
  3. Place the holders on a table with threads upwards Insert the filters in the holders with the most reflecting side down (towards adapter when installed).
  4. Write stickers with filter names and NOT numbers. Put them on the holders.
  5. Install the filters in the instrument:
    • If HiRAC is mounted, exit BIAS and turn motor controller off.
    • On HiRAC remove cover plate to filterwheel by unscrewing the 8 cap-head bolts.
    • Turn the filterwheel manually by hand to the position to be used.
    • If any filter is present in that position, remove it using the HiRAC Filter Tool from the tool rack in the dome.
    • Insert the new filter with the thread downwards and screw on the cover plate again.
    • If HiRAC is mounted, remember to the turn motor controller back on again.
  6. Update the filter setup file (see ref. page) and the filter whiteboard and print out the setup-form and insert in the HiRAC-binder.

Filter Setup File

Update the filter setup file (see ref. page ). Until filter focus offset are implemented only change filter names in the file.

Aligning Filters

This is only necessary when using tip/tilt

Due to the small size of the pickup mirror, the position of the filter in the filterwheel critically affects if the reflected light is picked up by the mirror or not. Therefore the individual offsets to the guideprobe position corresponding to each new filter must be determined as follows:

  1. Start up bias (see ref. page ).
  2. Acquire a star to do the alignment. It can be a science star (e.g. 9th mag) or the artificial star from the MIA-device. If the latter is chosen do:
    • place the device on HiRAC and fasten it with one screw.
    • Connect the power supply to the adapter Main power supply, with both plugs.
    • Connect the round plug from the power supply to the MIA-device.
    • make a 3s fullframe exposure with HiRAC.
    • if the artificial star is not seen in the frame, check that the device is positioned correctly.
  3. Make a fullframe image (if not made already)
  4. Type 'imexa' and position the cursor over the alignment star
  5. Press 'g' and then 'p'
  6. Type 'hfast'. This shows the FastCAM images in real time.
  7. Check that the star is on CCD pixel (9.5 , 6.5)
  8. If not, move the guideprobe with the commands xgo nn and ygo nn (see command list) or dxgo nn and dygo nn.
  9. If no guidestar is seen, refocus the guidecamera with zgo , and/or run the 'BIAS'-batches, to find the star.
  10. Write down the current x-position, y-position and z-position as X_FIL, Y_FIL and ZOFF.
  11. Repeat this for all filters. If there are no aligned filters present in HiRAC pick one filter and write down how much you had to offset in x, y - these values are XOFF_REF and YOFF_REF.
  12. If there is an aligned filter in HiRAC use this as reference filter. x-position for this filter is X_REF and y-position is Y_REF.
  13. Open the file mountdb (see ref. page ) and find the reference filter here. If the reference filter already is aligned, then XOFF_REF = XOFF and YOFF_REF = YOFF
  14. For all other filters calculate XOFF and YOFF using the relations:
  15. Update the file mountdb.

Back to top Last modified: 05-Jul-2001