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Next: Appendix.B. FLAIR-II fibre-ing. Up: Flair User Manual - Previous: References

Appendix A. FLAIR-II fibre-ing summary

There are two FLAIR-II plateholders (PH's): 14/5 has a single 92 x 100um fibre bundle and separate 5 x 33um fibre fiducial bundle whilst PH 14/6 is a hybrid with both 73 x 100um and 71 x 55um fibre bundles going to separate slit assemblies as well as an 8 x 33um fibre fiducial bundle. The 33um fiducial fibres have a blue cladding, 100um fibres have a gold coloured cladding whilst the 55um fibres in PH 14/6 have a clear (colourless) cladding.

During fibre-ing the following points should be bourne in mind. They offer tips and guidelines which lead to safe, reliable and more accurate operation and can save considerable time during fibre-ing.

1. Preliminaries

  1. Always wear UV safety goggles during the entire fibre-ing process.
  2. Before you start the AF program remember to copy the appropriate ferrule-number to fibre-number look-up-table (LUT) for the chosen fibre bundle and/or PH being used to the file FIBRES.DAT (e.g. choose from FIB92.DAT for PH 14/5 and FIB55.DAT or FIB100.DAT for PH 14/6).
  3. Each PH requires a slightly different focus setting to properly image the emulsion surface of the mounted FLAIR mask so remember to adjust accordingly before you start.
  4. Ensure that the Mercury lamp's cooling fan is switched on to prevent the lamp, which generates considerable heat, from overheating.
  5. Start the AF program on the AutoFred PC.
  6. Always check the 3 set gripper heights (L,C,P) at the start of each fibre-ing session or whenever the AF program has been re-started.
  7. Read the instructions on the AutoFred menu screens carefully until fully familiar with the program.
  8. At the start check for excessive `play' with plate movement in the PH and secure if necessary with cotton buds or toothpicks at each corner.
  9. Always check the gripper jaws for build-up of glue before you start and clean off as necessary.

2.Fibre-ing: suggested techniques

  1. Ferrules should be gripped only by the metal shank to avoid damage to the delicate fibres. The pairs of forceps provided should be used.
  2. Do not attempt to pull fibres out further than they extend naturally. No force is necessary!
  3. Try to fibre-up in sequence, e.g. start with ferrule No.1. and increase sequentially till the last fibre number in the chosen bundle. AF logs each ferrule automatically after gluing, incrementing the ferrule No. (this can be manually altered). Keeping the fibre-ing in sequence minimises editing and saves time.
  4. Try to plan the fibre-ing in advance. Sensible planning can avoid problems with fibre-object positioning and saves time in the long run.
  5. Keep azimuth changes to a minimum. Large azimuth variations can cause problems with AF keeping the fibre-ferrule assembly in the field of view.
  6. Try to keep the ferrules parallel to PH's East-West edges. This minimises azimuth changes and leads to less complicated fibre arrangements which minimises fibre-vignetting, reducing the need for excessive taping-down of loose fibres (all saving valuable time).
  7. Do one fibre-ferrule bank at a time starting with the banks on the south edge.
  8. Remember the footprint of the gripper. It is easy to crash the gripper into an already glued fibre when descending to plate height or to hit still bedded ferrules when working close to either the north or south PH edges. You can work closer to the N-S plate edges by temporarily removing ferrules that might obstruct the gripper from their beds.
  9. Do not over illuminate the slit output end to back-illuminate the fibre cores as this may introduce centroiding errors through saturation effects in the over-illuminated core-fibre image.
  10. Remember that once the fibre has been glued the gripper jaws open on one side to release the ferrule before ascending to `load' height. This may dislodge an adjacent ferrule if positioned too close.
  11. Remember to keep a path clear for the image guide. Any fibres along this path may be vignetted and may even prevent the image guide from housing correctly in the IGS.
  12. Remember that ferrules in banks with double the fibre density only extend half way across the field of the PH.
  13. Remember to place some sky fibres ( ~ 10). This is important to ensure good sky subtraction from object spectra. These should be placed uniformly over the field and in areas of high target object concentration (given numerical code `999' in the fibre-ing log).
  14. In the fibre record log sheet note the ferrule and object No's for the fibre about to be glued.
  15. Remember to keep a map of the fiducial and sky fibre numbers and locations in the field. The fiducial locations can assist with interpreting field rotation during observing whilst sky fibre locations may be useful with optimising sky-subtraction.
  16. Do not touch the X-Y table during gluing as this may cause slight mis-alignments between the object's image centroid and the fibre image centroid.
  17. Because of the problem of scattered light between the closely spaced fibres on the spectrograph CCD the brightest objects can be chosen to occupy doubly spaced fibres and minimise the scattered light directly. This is easy now that both the ferrule number and fibre number are given next to each ferrule on the PH's.
  18. After gluing all fibres return the syringe of optical adhesive to its box else remaining cement will slowly cure in normal light.
  19. Clean all prism top surfaces after all fibres have been affixed, this will ensure maximum light transmittance. Cleaning can be done with cotton buds dipped in a suitable solvent. Methanol is usually O.K. but for glue stuck on the top surface dichloromethane is better.

3.Troubleshooting

  1. If the gripper jaws become sluggish or stop working completely, check that the nitrogen supply line has not become `kinked'. If it has, wind back the gripper and test the jaws. If there is no response and the supply line appears O.K. check the Nitrogen gas display gauge on the wall and the supply switch.
  2. If ferrules are not seating properly on the plate during fibre-ing check for cured glue build-up on the base of the gripper jaws and clean off as necessary. If problem persists check glue build-up on teflon pads. If these are all clean check that the gripper is descending properly to the plate and adjust as necessary. If there is still a problem then it may be with the mechanics of the gripper itself. The FLAIR instrument scientist should then be contacted in the first instance for advice/assistance.
  3. If the image of the fibre-core appears `double' when on the plate then this indicates a mis-alignment of the input optical beam with the prism-ferrule assembly. Check for proper seating of the ferrule on the plate. If this is O.K. then the prism may need to be re-aligned on the ferrule. The FLAIR support astronomer or FLAIR instrument scientist should be consulted in such eventualities.
  4. If the AutoFred PC cursor stops responding then the AutoFred PC will need to be re-booted. Send the gripper back to load height. Type `Ctrl-C' and re-boot the computer and re-start the AF program. Do not say this is the start of a new run to ensure that the ferrule-fibre log file remains current.
  5. If prism(s) are loose or become loose make a note of which ones and inform the duty FLAIR support astronomer or FLAIR instrument scientist. Completely dislodged prisms should be carefully stored for later re-attachment.


next up previous contents
Next: Appendix.B. FLAIR-II fibre-ing. Up: Flair User Manual - Previous: References



Chris Tinney
Mon Aug 19 14:56:26 EST 1996