README file for Crater (Weisz et al. 2016) - An HST Study of the Crater Stellar System
MAST webpage: https://archive.stsci.edu/prepds/crater/index.html
Refer to this HLSP with DOI: http://dx.doi.org/10.17909/t9-jtv3-fm83


## Introduction
The Crater object is a faint star system, discovered relatively recently (Belokurov et al. 2014, Laevens et al. 2014), located in the Milky Way's outer halo. The collection presented here is based on optical imaging data of Crater taken with the Advanced Camera for Surveys on the Hubble Space Telescope. The available data includes the resulting catalog of Crater members, a catalog of artificial star tests, as well as an ACS reference image in F814W used for photometry. This study concludes that Crater is an unusually-young globular cluster (and not a dwarf galaxy), given it's location, though its origins remain elusive.

## Data Products
Data files in the Crater HLSP collection adhere to the following naming structure:
    - hlsp_crater_hst_acs_crater_f606w-f814w_v1_<ext>
The Crater collection contains the following types of data files:
    - _ast.fits
        - This file contains a catalog of the Artificial Star Test objects used to characterize completeness and photometric uncertainties.
    - _cat.fits
        - This file contains the catalog of detected objects with constraints applied to the SNR, sharp, and crowd parameters.
    - _drc.fits
        - This file contains an ACS image of Crater in F814W used for photometry.