# Run-time Environment

Setting of run-time environment can be used to modify of global parameters.

## FITS environment variables

FITS environment variables are commonly used to redefine a value of keywords of a FITS header. For instance, FITS_KEY_FILTER - redefines FILTER keyword, etc. Other variables available (sometimes required during processing) are listed in table. For example, when your local conventions stores the exposure time in record labeled by EXPOSURE keyword

    ...
    EXPOSURE =               20.000 / [s] Exposure time
    ...

use FITS_KEY_EXPTIME="EXPOSURE". Variables can be preset as:

    $ FITS_KEY_DATEOBS="DATE-BEG"
    $ export FITS_KEY_DATEOBS

For convenience, these variables can be set under Unixes as system-wide in /etc/profile (or /etc/bash.profile, /etc/bashrc or etc.) or on per-user base in $HOME directory: $HOME/.profile (or $HOME/.profile or $HOME/.bashrc or etc).

The identifiers (following prefix FITS_KEY_) should be unlike to FITS keywords. That conversion suppress confusion of the minus sign character (-) inside shell scripts.

The area of detector is π(R2-r2) for Newtonian reflector, where R is radius of a primary mirror and r is radius of projection of secondary mirror (of secondary shadow). The area of detector will be used for photometry calibration.

## Run-time

`MUNIPACK_LIBEXEC, MUNIPACK_BIN`

Set path(s) for executable Munipack's modules. The values are set during installation and used very rarely, perhaps for testing purposes.

`MUNIPACK_CATCONF_PATH`

A path pointing to the local configuration file for Virtual Obseravtory catalogues.