II. Contents of the First 2MASS Incremental Data Release

4. Atlas Images

The 2MASS Spring 1999 data release includes 233,979 FITS images in the three survey bands constructed from the scans of 8.5´ × 6° long Survey Tiles. 223,806 of the images are 512×1024 (1"/pix) in size, and a small number, 10,173, from the ends of scans are 512×698 (1"/pixel). The J, H and Ks images for each region of sky are resampled to the same scale and registered to facilitate 3-color investigations. Positional and photometric calibration data are carried in the FITS header for each image.

Because of the prohibitive size of image data, currently only ~20:1 lossy-compressed versions of the Atlas Images are accessible on-line. Compression of the images was carried out using the hcompress procedure. It is hoped that it will be possible to serve the full resolution Atlas Images in the future.

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