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- SDSS Imaging Data (`pydl.photoop`)

# 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

digraph inheritancef91f0b4a18 { rankdir=LR; size="8.0, 12.0"; "PhotoopException" [URL="../api/pydl.photoop.PhotoopException.html#pydl.photoop.PhotoopException",fontname="Vera Sans, DejaVu Sans, Liberation Sans, Arial, Helvetica, sans",fontsize=10,height=0.25,shape=box,style="setlinewidth(0.5)",target="_top",tooltip="Exceptions raised by :mod:`pydl.photoop` that don't fit into a"]; "PydlException" -> "PhotoopException" [arrowsize=0.5,style="setlinewidth(0.5)"]; "PydlException" [URL="../api/pydl.PydlException.html#pydl.PydlException",fontname="Vera Sans, DejaVu Sans, Liberation Sans, Arial, Helvetica, sans",fontsize=10,height=0.25,shape=box,style="setlinewidth(0.5)",target="_top",tooltip="Base class for exceptions raised in PyDL functions."]; }

### 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.