SDSS Imaging Data (pydl.photoop)

Introduction

The photoop package is used to process SDSS imaging data. This package is used to reduce, resolve and flux-calibrate the SDSS raw data, resulting in both flux-calibrated images and catalogs.

SDSS ceased taking imaging data in 2009, and there has only been one full processing of the imaging data since then, although adjustments have been made to the astrometry and flux calibration.

The primary emphasis of this implementation is:

1. Functions related to the SDSS photometric objID, which is a unique integer used in SDSS databases, constructed from quantities that specify a particular astronomical object on a particular image.
2. Functions related to finding SDSS photometric data on disk.
3. The SDSS “window” function, which defines what parts of the sky are covered by SDSS images. This can be used in conjunction with the mangle module to find points and regions that have SDSS imaging.
4. In general, functions that work with existing imaging data, rather than functions to reduce the data.

The photoop package is itself divided into a number of subpackages. Below we list the subpackages and the usability of the PyDL equivalent. The readiness levels are defined as:

Obsolete

No point in implementing because the purpose of the code lapsed many years ago.

Not Applicable (NA)

No point in implementing because another built-in or numpy/scipy/astropy package completely replaces this.

None

Not (yet) implemented at all.

Rudimentary

Only a few functions are implemented.

Fair

Enough functions are implemented to be useful, but some are missing.

Good

Pretty much anything you could do with the photoop code you can do with the equivalent here.

Subpackage	Readiness Level	Comments
apache	Obsolete	Processing of “Apache Wheel” images, used for calibration.
astrom	None	Astrometry for SDSS images.
atlas	None	Construction of “atlas” images, small cutouts of individual objects.
bluetip	None	Tools for “blue-tip” photometry and extinction estimation.
compare	Obsolete	Compare the same images in two different data reductions.
database	Obsolete	Experimental database loading code.
flats	None	Analysis of flat-field files.
hoggpipe	Obsolete	Another version of “Apache Wheel” processing code.
image	None	Tools for creating “corrected frame” images. These are flux-calibrated and sky-subtracted images with physical flux units.
ircam	Obsolete	Tools for processing all-sky “cloud camera” images, used to establish photometricity.
match	None	Tools for matching SDSS spectra to corresponding photometric objects.
misc	None	Code with no obvious home in any other category.
pcalib	None	Tools related to “ubercalibration”.
photoobj	Rudimentary	Tools for creating calibrated catalogs from images.
plan	Obsolete	Tools for planning photometric reductions.
plots	None	Plots for high-level quality assurance.
psf	None	Analysis of point-spread functions.
ptcalib	Obsolete	Processing of “photometric telescope” data, an obsolete technique for flux-calibration.
resolve	None	Code for the resolve stage of image processing.
sdss3_runqa	Obsolete	Quality assurance tests from the most recent photometric reduction.
sdssio	Rudimentary	Tools for reading and writing various data files produced by the photometric reductions.
window	Rudimentary	Tools for determining the sky coverage of the survey.

API

pydl.photoop Package

This subpackage implements functions from the photoop package.

Classes

PhotoopException

Exceptions raised by pydl.photoop that don’t fit into a standard exception class like ValueError.

Class Inheritance Diagram

pydl.photoop.photoobj Module

This module corresponds to the photoobj directory in photoop.

Functions

sdss_calibv()	Return calibration for velocities from pix/frame to deg/day.
unwrap_objid(objid)	Unwrap CAS-style objID into run, camcol, field, id, rerun.

pydl.photoop.sdssio Module

This module corresponds to the sdssio directory of photoop.

Functions

filtername(f)	Return the name of a filter given its number.
filternum([filt])	Return index number for SDSS filters either from a number or name.
sdss_calib(run, camcol, field[, rerun])	Read photometric calibration solutions from calibPhotom or calibPhotomGlobal files.
sdss_name(ftype, run, camcol, field[, …])	Return the name of an SDSS data file including path.
sdss_path(ftype, run[, camcol, rerun])	Return the path name for SDSS data assuming SAS directory structure.
sdssflux2ab(flux[, magnitude, ivar])	Convert the SDSS calibrated fluxes (magnitudes) into AB fluxes (magnitudes).

pydl.photoop.window Module

This module corresponds to the window directory in photoop.

Functions

sdss_score(flist[, silent])	Score a list of imaging fields from zero to one.
window_read(**kwargs)	Read window files in $PHOTO_RESOLVE.
window_score(**kwargs)	For uber-resolve, score all the fields from zero to one.