2dfdr Quick Guide

Contents:

Installing 2dfdr

The file will have a name something like: 2dfdr-linux-5.33.tgz

Unpack the tar file and extract the software to your chosen software directory:

> tar -xvzf 2dfdr-linux-5.33.tgz

To install 2dfdr, add the full directory pathname of 2dfdr_install/bin to your PATH (ensuring that you do not have the environmental variables DRCONTROL_DIR or DRCONTROL_ENV already set). To do this:

    tcsh
    > set path = ($path /path/to/software/2dfdr_install/bin)
    bash
    > export PATH=/path/to/software/2dfdr_install/bin:$PATH

Running 2dfdr

2dfdr should be run in a separate working directory for each set of observations with a particular field plate. A meaningful directory structure for your observing run can save a lot of heartache later on. An example directory structure might be:

    Observing95june05/
        night1/
            field1/
ccd1/
ccd2/

Note that due to the way the flat and arc frames are used, each independent observation (i.e. with a different configuration of the fibres on the field plate) will require a new directory, even if all you have done is tweak the positions of fibre on a previously observed configuration. Once the AAOmega slit wheel is moved with a change of field plate, a new set of flats and arcs are required for the reduction. Data from multiple repeats of the same field, or for fields that contain some repeat observations can be automatically combined, but this is done after the full reduction of data for each field.

Data from the blue and red arms can be reduced in the same directory, but this is often not easy to work with and so most users create separate ccd1 and ccd2 sub directories with blue and red data, respectively.

If you have bias or dark calibration files, these need to be reduced in a separate directory (the reduced, combined output is then copied into the working directory of choice) i.e.

    Observing95june05/
                bias/
		dark/

Move to your working directory of choice and then the software can be started with the command

    > drcontrol

For further detail on using 2dfdr to reduce your data, see the cookbooks available under the instrument webpages.

Bug reports about 2dfdr should be addressed to the AAOmega team.

Frequently Asked Questions

Questions:

Is it possible to look at the data after each reduction step in 2dfdr?

How does the emission-line throughput calibration work in 2dfdr?

What does flat-fielding mean in 2dfdr?

How can one omit 'sky' fibres which contain objects in 2dfdr

How does 2dfdr handle flexure?

Can one save 2dfdr parameter settings?

Can one combine frames BEFORE sky subtraction in 2dfdr?

Answers:

Is it possible to look at the data after each reduction step in drcontrol?

One can turn on various automatic plot options - the fitted tramlines, the fit to the scattered light background and the profile fits during extraction (with the FIT method), the throughput map and the subtracted sky under the plot tab. If you want to look at the raw extracted spectra (i.e. before calibration/sky-subtraction) use the plot tab to look at the *ex.fits files after reduction.

How does the emission-line throughput calibration work in 2dfdr?

All sky lines are used. Sky-line pixels are identified by plotting the wavelength derivative of the flux - those with large derivatives are identified as sky-emission-line-pixels. Obviously if your wavelength range contains no sky lines (e.g. at high-dispersion in the blue) this option should not be used! In that case twilight flats and offset sky frames will be needed. Note, it is only possible to do twilight flats for a maximum of 4 fields a night, two at the start and two at the end, since the fields must be pre-configured in order to take twilight flats, and the flat is not relevant once fibres have been moved, even if the field is reconfigured at a later date.

What does flat-fielding mean in 2dfdr?

There are three-meanings. The first is the dispersed white-light fibre spectra used to fit the tramlines. This is what is usually referred to as the `FLAT'. The second meaning is `pixel-to-pixel CCD flat field' otherwise known as a 'longslit flat'. The third meaning is `fibre flat-field' by which we mean dividing the extracted object spectra by extracted, normalized, white light spectra (this is usually the same as that used for the tramlines). Given the uniformity of modern CCDs the work of the 'longslit flat field' can be done with the 'fibre flat'.

How can one omit 'sky' fibres which contain objects in 2dfdr?

Normally this should not be necessary as drcontrol takes a median sky, and clips outliers. If you really must, create a file called `skyfibres.dat' in the working directory, listing the numbers (one per line) of the fibres you wish to use for sky. drcontrol will then use this file, in preference to the headers, when you reduce (or re-reduce) the data.

Can one save 2dfdr parameter settings?

No, but you can create .idx files with these settings preset

Can one combine frames BEFORE sky subtraction in 2dfdr?

No. If you want to experiment with this turn sky-subtraction off completely and do your own processing on the final individual spectra. If you get better results than using 2dfdr, let us know