If you’ve tried the new GALEX survey from the command line, you may have noticed some messages
Warning: Multiple occurrences of key: EPOCH
popping up. Many of the GALEX FITS files have two EPOCH keywords in their headers. Fortunately they both have the same value, so this is innocuous enough. Still the FITS reader gets a bit nervous when it sees this.
It’s a little more embarrassing since the EPOCH keyword is deprecated in FITS. Epoch usually means the time of the observation, but it was explicitly defined to be the epoch of the coordinate system in the original FITS definition. To relieve the confusion this engendered EPOCH was deprecated. We’re supposed to use EQUINOX for the epoch of the coordinate system and DATE-OBS for the epoch of the observatoin.
So having even one EPOCH keyword is bad form much less two!