Known Issues and Workarounds

Catalogs with Zero Sources

Problem
Some Tractor catalogs contain pixels but zero sources.
Explanation
Because, in some cases, very few pixels touch a brick, it is entirely possible to have zero sources in a Tractor file. For this reason, when processing multiple Tractor files as a batch, it is recommended to always read in the FITS header and check that NAXIS2 > 0.

DR2 coadd files have been deprecated

On August 23rd, 2018, the DR2 coadd directory was removed to save space. Data from that directory is still available via FTP from the NOAO archive.