NAME

Astro::FITS::HdrTrans::UFTI - UKIRT UFTI translations

SYNOPSIS

  use Astro::FITS::HdrTrans::UFTI;

  %gen = Astro::FITS::HdrTrans::UFTI->translate_from_FITS( %hdr );

DESCRIPTION

This class provides a generic set of translations that are specific to the UFTI camera of the United Kingdom Infrared Telescope.

METHODS

this_instrument

The name of the instrument required to match (case insensitively) against the INSTRUME/INSTRUMENT keyword to allow this class to translate the specified headers. Called by the default can_translate method.

  $inst = $class->this_instrument();

Returns "UFTI".

COMPLEX CONVERSIONS

These methods are more complicated than a simple mapping. We have to provide both from- and to-FITS conversions. All these routines are methods and the to_ routines all take a reference to a hash and return the translated value (a many-to-one mapping). The from_ methods take a reference to a generic hash and return a translated hash (sometimes these are many-to-many).

to_DEC_SCALE

Sets the declination scale in arcseconds per pixel derived from keyword CDELT2. The default is time dependent, as tabulated in the UFTI web page. http://www.jach.hawaii.edu/UKIRT/instruments/ufti/PARAMETERS.html#1 The default scale assumes north is to the top.

The actual CDELT2 value is scaled if its unit is degree/pixel, as suggested by its size, and the presence of header CTYPE2 set to 'DEC--TAN' indicating that the WCS follows the AIPS convention.

to_FILE_FORMAT

Determines the file format being used. It is either "HDS" (meaning an HDS container file of NDFs) or "FITS" and is determined by the presence of the DHSVER header.

to_POLARIMETRY

Checks the filter name.

to_RA_BASE

Converts the decimal hours in the FITS header RABASE into decimal degrees for the generic header RA_BASE.

Note that this is different from the original translation within ORAC-DR where it was to decimal hours.

There was a period from 2000-05-07 to 2000-07-19 inclusive, where degrees, not hours, were written whenever the data were stored as NDF format. However, there wasn't a clean changover during ORAC-DR commissioning. So use the FILE_FORMAT to discriminate between the two formats.

from_RA_BASE

Converts the decimal degrees in the generic header RA_BASE into decimal hours for the FITS header RABASE.

  %fits = $class->from_RA_BASE( \%generic );

There was a period from 2000-05-07 to 2000-07-19 inclusive, where degrees, not hours, were written whenever the data were stored as NDF format. However, there was not a clean changover during ORAC-DR commissioning. So use the generic header FILE_FORMAT to discriminate between the two formats. For symmetry and consistency, retain these units during the problem period.

to_RA_SCALE

Sets the right-ascension scale in arcseconds per pixel derived from keyword CDELT1. The default is time dependent, as tabulated in the UFTI web page. http://www.jach.hawaii.edu/UKIRT/instruments/ufti/PARAMETERS.html#1 The default scale assumes east is to the left.

It corrects for an erroneous sign in early data.

The actual CDELT1 value is scaled if its unit is degree/pixel, as suggested by its size, and the presence of header CTYPE1 set to 'RA---TAN' indicating that the WCS follows the AIPS convention.

from_RA_SCALE

Converts the generic header RA_SCALE to the FITS header CDELT1 by ensuring it has a positive sign as in the input data. This sign is wrong because the right ascension increases with decreasing pixel index, however this conversion permits a cycle from FITS to generic and back to FITS to retain the original value.

  %fits = $class->from_RA_SCALE( \%generic );

to_UTDATE

Converts FITS header values into Time::Piece object. This differs from the base class in the use of the DATE rather than UTDATE header item and the formatting of the DATE keyword is not an integer.

from_UTDATE

Converts UT date in Time::Piece object into YYYY-MM-DD format for DATE header. This differs from the base class in the use of the DATE rather than UTDATE header item.

to_UTEND

Converts UT date in DATE-END header into Time::Piece object. Allows for blank DATE-END string present in early UFTI data.

to_UTSTART

Converts UT date in DATE-OBS header into Time::Piece object. Allows for blank DATE-OBS string present in early UFTI data.

to_X_REFERENCE_PIXEL

Specify the reference pixel, which is normally near the frame centre. There may be small displacements to avoid detector joins or for polarimetry using a Wollaston prism.

from_X_REFERENCE_PIXEL

Always returns CRPIX1 of "0.5".

to_Y_REFERENCE_PIXEL

Specify the reference pixel, which is normally near the frame centre. There may be small displacements to avoid detector joins or for polarimetry using a Wollaston prism.

from_X_REFERENCE_PIXEL

Always returns CRPIX2 of "0.5".

SEE ALSO

Astro::FITS::HdrTrans, Astro::FITS::HdrTrans::UKIRT.

AUTHOR

Malcolm J. Currie <mjc@star.rl.ac.uk> Brad Cavanagh <b.cavanagh@jach.hawaii.edu>, Tim Jenness <t.jenness@jach.hawaii.edu>.

COPYRIGHT

Copyright (C) 2008 Science and Technology Facilities Council. Copyright (C) 2003-2007 Particle Physics and Astronomy Research Council. All Rights Reserved.

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either Version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.