It's over 4 years since I gave up on collecting my own data, but one thing I do recall was to regularly retake flat frames. How frequently depended upon how much imaging had been undertaken since the last collection, so there often could be a long gap.

The site in Spain often has long spells of clear skies :), but maybe the downside of this is that the scopes are 'open' to the elements for extended periods. What do others think of having flat frames collected on a regular basis, particularly the syndicate piers. There are always opportunities to do so, either around full moon, or, during periods of bad weather. Any thoughts?

Ray