Data Reduction System

The FEROS Data Reduction System (DRS) is implemented within ESO-MIDAS. It consists of a MIDAS context (feros) and a set of "local" procedures which can be copied from the MIDAS distribution to the user's midwork directory in order to use them. Alternatively the following archive can be used to set up a FEROS DRS environment identical to the one provided at the telescope. A few additional shell scripts and utilities are provided to make life easy, see the README:

• FEROS-DRS.tgz (Version 1.60/Thu Feb 2 12:28:02 2006)
  (in some Linux versions, e.g. SuSE, you may need to replace bin/ferosPrepDateDir with this version of the file)

The above package has been tested on MIDAS versions 01FEBpl1.0 & 02FEBpl1.0. In principle it should be compatible with all versions later than these, and will probably be compatible with versions back to 98NOV.

The DRS page for FEROS at the ESO-1.52m can be found here.

File Naming conventions

File naming conventions for DRS products are given here and in Appendix 1 of the FEROS-DRS package README.

Guess Sessions

From time to time, if for any reason certain of the FEROS components shift (e.g. earthquakes, total disassembly and reassembly to move from one telescope to another, etc) the cross order profile suffers a significant change (see here) such that the initial guess for the orders is no longer sufficiently accurate. For each shift a new Initial Guess session should be created/used. Here are guess sessions appropriate for various epochs during the life of FEROS...

• At the MPG/ESO-2.20m
  
  • 2005-10 --: The same Guess Sessions can be used for all readout modes of a given binning, but the different binnings require different Guess Sessions:
    
    • 1x1 binning: ThAr9021
    • 2x2 binning: ThAr9121
  • 2003-03 -- 2005-09: guess0196.tar.gz
  • 2003-02: guess1651.tar.gz
  • 2002-10-?? -- 2003-02-??: guess9001.tar.gz
• Default from ESO-1.52m: guess9857.tar.gz

Online Reductions at the telescope

The principal purpose of the FEROS DRS is to provide an online, real-time reduction of the observations as they are acquired at the telescope. Various simplifying assumptions are made and as a result, these reductions, or DRS products, are intended only as a "quick look tool". They are not intended to be of Publication Quality. More to the point ESO definitely does NOT guarantee them to be of publication quality. They can be used to check approximate Signal to Noise level and simple things like that.

Offline Reductions at home

The FEROS DRS can none the less be used to obtain Publication Quality reductions. In particular close attention should be paid to the following issues:

• Order location and order tracing.
• Compare calibrations obtained during the afternoon before the observations with those acquired in the morning after for drifts in order location or changes in the wavelength solution.