README FOR THE CFHT MEGAPRIME CAMERA
====================================

This README describes characteristics of the MEGAPRIME@CFHT camera.
Please note that this camera is operated 'in two modes' since 2015.
The two modes significantly differ from each other and need particular
treatment for data processing or any analysis programs. The
description of these modes and the treatment within THELI is described
in this file.

File version: 10/06/2015

THE TWO MODES
=============

In the following North is always up and East to the left.

- The first mode is the traditional 36-chip setup that we have known
  since 2003. The THELI numbering of the chip-layout from this mode is
  as follows:

  28  29  30  31  32  33  34  35  36
  19  20  21  22  23  24  25  26  27
  10  11  12  13  14  15  16  17  18
   1   2   3   4   5   6   7   8   9

- In the second mode (new since 2015) all 40-chips of the instrument
  are used. The THELI labelling of the mosaic for this mode is:

      32  33  34  35  36  37  38  39  40
  21  22  23  24  25  26  27  28  29  30  31
  10  11  12  13  14  15  16  17  18  19  20
       1   2   3   4   5   6   7   8   9

THE FILTERS
===========

The new mode also comes with a complete set of new filters. Hence,
the 'first mode THELI filter naming scheme', which used one-letter
abbreviations for all filter names, is no longer feasible.

We therefore now use the following filter naming conventions:

- Up to data version 2.X only first mode data are processed and we use
  the traditional naming scheme:

    THELI naming    CFHT Filter name
       u              u.MP9301 
       g              g.MP9401
       r              r.MP9601
       i              i.MP9701
       y              i.MP9702
       z              z.MP9801

- From Version 3 onwards, any THELI reduced MEGAPRIME data uses the
  original CFHT filter names which leads to the following naming
  scheme:

    THELI naming    CFHT Filter name   comment
      u.MP9301          u.MP9301 
      g.MP9401          g.MP9401
      r.MP9601          r.MP9601
      i.MP9701          i.MP9701
      i.MP9702          i.MP9702
      z.MP9801          z.MP9801

      u.MP9302          u.MP9302       mode 2 filter
      g.MP9402          g.MP9402       mode 2 filter
      r.MP9602          r.MP9602       mode 2 filter
      i.MP9703          i.MP9703       mode 2 filter
      z.MP9901          z.MP9901       mode 2 filter

This finally also removes the permanent i/y confusion we had!

Filter curves for the new 'mode 2' filters can be found at:
http://www.cfht.hawaii.edu/Instruments/Filters/megaprime.html