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Frequently Asked Questions about 2dF/AAOmega

Questions

Answers

What is the reconfiguration time?

For a full field reconfiguration (i.e. to remove the old configuration and replace it with a new one) the reconfiguration time is now of the order 40mins.

What is the minimum spacing (in arcseconds on the sky) of 2dF fibres?

i.e. how close can observational targets be?

Actually it depends on the geometry at which the fibres come in due to the rectangular shape of the magnetic buttons. The absolute minimum is 30 arcsec (2mm), but typically it's 30-40 arcsec depending on location in the field and target distribution.

Which way does the slit-numbering go?

Both ways! Seriously - engineers and programmers decided on different conventions.
In drcontrol S=1 refers to the bottom fibre, as displayed. Ditto for the headers where the 1..400 arrays go from bottom to top. In general low pivot numbers (i.e. those near 1) will be displayed near the bottom of the screen by drcontrol while high pivot numbers (i.e. those near 400) will be displayed near the top, though there is not a one to one mapping. The actual mapping is stored in the 2dF system file spec_fibres.txt.

How do I work out which spectrum is from which object?

There are a number of ways to do this, the best method depends on what you are trying to do. The information is all stored in a binary table extension of the reduced (and raw) .fits files, and also in the .sds file from which the field is configured. The file format and various methods to retrieve the data are described on the AAOmega file format page.

Sarah Brough (sb@aao.gov.au)