The ccds- and survey- files described on the DR4 files page contain a column bitmask, which is defined as:
| Bit | Meaning |
|---|---|
| 0001 | this exposure is flagged in the bad_expid file |
| 0010 | a zeropoint solution was not computed for these exposures, and so the ccdname disagrees with the hdu number |
| 0100 | these ccds had outlying values for astrometric or photometric offsets (\(\sqrt(\) ccdrarms \(^2 +\) ccddecrms \(^2) > 0.1\) OR ccdphrms \(> 0.2\)) |
The CCDs used by legacypipe can be determined via:
photometric == True AND bitmask == 0
Note that photometric, ccdrarms, ccddecrms and ccdphrms are all columns in the ccds- and survey- files described on the DR4 files page.