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Configure and Locking Allocations

Please note: In the discussion that follows, it is assumed that you are trying to lock the allocation to the same field plate for which it was originally configured, and that you are observing at a similar Hour Angle (HA). Trying to lock the fibres to the same targets on different field plates or for a very different HA may fail to configure due to fibre collisions.

It can often be useful to lock a number of fibres (any number between 1 and 399) onto certain targets while still allowing Configure to freely allocate the rest of the fibres. The classic example is that a field has been observed for 2 hours on one night and it has returned redshifts for half of the targets but the remaining targets need to be observed for a second 2 hours, as per the original telescope proposal, while adding in additional targets for the remaining fibres.

It is possible to force the allocation of some fibres on to previously observed targets, and then reconfigure the remaining objects.

The procedure for creating and using an import file

  1. Load your .fld file as normal, and configure as normal.

  2. Save the .sds file.

  3. Save a .lis file using the File->List.. menu option.

  4. Edit the list file to create a new file, by default Configure is expecting a .imp file. The nature of the Edit is discussed below.

  5. Reopen your .fld file (NOT your .sds file).

  6. Turn on Expert mode in Configure (select the Expert flag in the Options menu).

  7. From the Commands menu, select Import Allocations... and select your .imp file. This will allocate the fibres as specified in the .imp file.

  8. Now select Lock Allocations.

  9. You can now proceed with the normal configuration, as you did in step 1 above, but the locked fibres will stay in place.

Creating your .imp file

The file saved by the File->List option in Configure, a .lis file by default, is a plain text file which shows which fibres are allocated to which targets. The format is close to that of a .fld file, but with an additional column of * and a column of Fibre numbers between the * and the Object Names.

The .imp file format is almost identical to that of a standard .fld file, but with the addition of an extra column of fibre numbers. This column should be the very first column, i.e. it goes before the Object Name column of a standard .fld file.

To convert the .lis file into a .imp file, simply delete the first column of * characters that have been added.

Modify the contents of the .imp file to only list those fibres needing to be locked, or else all 400 fibres will stay locked. For some programs it may be possible to edit the .imp file by hand in a text editor. For most programs, you will probably want to write a simple script to remove or re-prioritize allocations based on the results of an initial examination of the spectra from a first observation.

Sarah Brough (sb@aao.gov.au)