LBCgo: LBC data reduction pipeline

WARNING: This code is currently under continued development. While the basic functionality exists, it should be used with some care and attention.

Dependencies:

Python dependencies:

• astropy
• CCDProc
• numpy

External dependencies:

• SExtractor
• SCAMP
• SWarp

The external C++ codes SCAMP, SWarp, and SExtractor developed by Emmanuel Bertin and collaborators are available through http://astromatic.iap.fr. SCAMP and SExtractor are also available through GitHub: https://github.com/astromatic.

Installing:

LBCgo is available through pip. The easiest path to installation is:

pip install lbcgo

Running LBCgo:

For "standard" situations, the LBCgo can be run in one step from the python command line. In this case, all of the data in the raw/ directory are taken on the same night and have appropriate calibrations. In this case, running LBCgo from the command line is as simple as:

ipython> from lbcproc import *
ipython> from lbcregister import *

ipython> lbcgo()

Before doing this, copy the parameter files from LBCgo/LBCgo/conf/ into the current working directory (an eventual fix won't require this step).

Alternatively, it can be useful to process each filter separately or even to avoid doing the astrometric steps until a later time. In this case, one may do:

ipython> lbcgo(filter_names=['I-BESSEL'], do_astrometry=False)

The astrometric portion of the reduction can be done later using, for example reducing the I-BESSEL data for the target PG1338+101:

ipython> fltr_dirs=glob('PG1338+101/I-BESSEL/')
ipython> go_register(fltr_dirs, do_sextractor=True,
            do_scamp=True, do_SWarp=True)

Missing chips:

LBCgo can be used if the images were taken when one of the LBC CCDs was off-line. The approach to doing this is to explicitly specify the chips to include in the data reduction steps:

ipython> lbcgo(lbc_chips=[1,2,4])

This is useful, as there were several months in 2011 when LBCCHIP3 was inoperable.

Some things that might go wrong:

Testing has revealed some occasional issues with the astrometric solution for the individual chips. This can be difficult to diagnose. The registration step using SWarp can warn you of some obvious cases, and these can subsequently be removed before rerunning the SWarp step by doing, e.g.:

ipython> go_register(fltr_dirs, do_sextractor=False,
            do_scamp=False, do_SWarp=True)

There are several issues related to missing or inappropriate files that the current code does not deal with gracefully. The most common is missing flat fields or missing configuration files (found in LBCgo/LBCgo/conf/).

Credit:

This pipeline is built on code initially developed by David Sands, and eventually incorporated into scripts made available by Ben Weiner (https://github.com/bjweiner/LBC-reduction).

LBCgo was designed to simplify the process of LBC reduction, removing the need for IDL or IRAF in favor of Python. This package continues to require SCAMP, SWarp, and SExtractor provided by Emmanuel Bertin (http://astromatic.iap.fr). It makes extensive use of the astropy-affiliated package CCDProc.

Known bugs / limitations:

• As of yet no tests are performed to separate LBCB / LBCR images taken with the V-BESSEL filter (which exists in both imagers). Care must be taken to avoid having both in the same directory.

• If flat field images are present, but no image is taken in that flat, an unfortunate behavior results (existing flat fields are divided by the unmatched flats).

• Flat field images taken as "test" images, including only a partial read-out of a single CCD, will cause the code to bail without a helpful error message.