Thanks Terry - very helpful. My setup is temporary, so it's flats each time.
Because I have to time sessions carefully around sleeping time for the shift worker in our home, I need to plan a work flow that optimises every moment on clear nights.
Darks and bias frames are not such a big deal - a library will usually do, I think. Flats require some preparation, and because the camera will possibly be rotated to frame an object, flats should really be taken following a session.
I'm thinking that an EL panel is probably the best solution for me
