2MASS Atlas Images derive from the coaddition of the six Read2-Read1 images which cover any given piece of the sky. Because of the prohibitive size of the full-resolution Atlas Image database (over 0.5 TB for just the First Incremental Data Release), 20:1 lossy-compressed images are kept on-line. The compression degrades the photometry of the sources particularly at lower SNR and this version of the image product should not be used independently to extract source photometry. Users should always defer to the Catalogs for source photometry.
Please see Section III.3.b for a detailed description of the procedures used to construct the Atlas Images.
[Last updated: 1999 May 7, by R. Cutri, M. Skrutskie and E. Kopan]