gfa_center

Overview

The pointing correction needed to center the focal plane on the field calculated from the GFA exposure.

Creators

  • PlateMaker external interface
  • PlateMaker internals
    • nomadCenter

Users

This list is not promised to be comprehensive.

Contents

Keyword/value pairs

Actual coordinates of the center minus header coordinates: the values are the errors, so the negative of the correction needed.

Keyword Sample value Type Units Description
ra -0.02 float arcseconds R.A. pointing error
dec 0.03 float arcseconds declination pointing error

FIXME: check the sign!

Storage and access

Through DOS

After gfaproc is run for a sequence, the get PML command may be used retrieve the guiding data from PlateMaker.

First, a PML connection must be established:

>>> from DOSlib.PML import dos_connection
>>> pm = dos_connection('PLATEMAKER')
>>> pm.execute('configure')
'SUCCESS'

The center data is normally calculated by PlateMaker when gfaproc is called. So, load some sample input for it, and run gfaproc:

>>> from PlateMaker import test_data
>>> nfsdata = test_data.nfs_data
>>> gfa_images = test_data.gfa_images
>>> stdstars = test_data.stdstars
>>> pm.execute('set', instrument=test_data.inst_name)
'SUCCESS'
>>> pm.execute('set', seqid=test_data.seq_id)
'SUCCESS'
>>> pm.execute('set', nfsdata=nfsdata)
'SUCCESS'
>>> pm.execute('set', gfa_images=gfa_images, stdstars=stdstars)
'SUCCESS'
>>> pm.execute('gfaproc')
'SUCCESS'

Now we can retrieve the center data from PlateMaker, which it will return in the form of numpy.recarray.

>>> gfa_center = pm.execute('get', 'gfa_center')
>>> gfa_center 
OrderedDict([('ra', ...), ('dec', ...)])

Preferred file representation

Name template:gfa-center-{PLATE_ID}.{CONFIG_ID}.par
Format:Yanny .par file

Example

::
>>> from PlateMaker import test_data
>>> fname = test_data.data_dir + '/gfa-center-52254.4.par'
>>> print(open(fname, 'r').read()) 
#Pointing correction (arcsec)
ra ...
dec ...