Some problems have been reported with zero-point variations across the field of view, mainly in the X-direction on the detector. We have done various tests, some of which appear to be affected and others that don't, but in general our test data seem to indicate this is not a problem with the camera itself but with flat fielding. Specifically, flat fields might be different when pointing towards or away from the sun when taking the flat fields and/or when taking them close to sunset/rise or closer to astronomical twilight, or at different angles of the rotator. However, to short this out properly we need flat fields at different times and with different set-ups, but existing flat fields are general taken under very similar circumstances. Some specific tests are needed.
A script that can be used during twilight and automatically takes a (set of) flat field exposure(s) at a proper light level has now been full documented and incorporated as a sequencer script. We plan to develop the option to take (sets of) flat fields for a series of filters which incorporates this script, and which could make taking flat fields during twilight largely automatic.
Following the analyze of the ALFOSC focus measurements (see below), we now plan to concentrate on the seeing measurements. The main objective will be to see if the telescope and instrument works well and what defines the best circumstances (e.g., if the site ports are open, at which wind speed, from what direction). This should indicate how we might improve things and optimize the telescope more, while this might also indicate what to expect given certain circumstances which could be used to assist in scheduling (queue-mode) service observations.
Thomas Augusteijn 2009-01-15