The exit pupil idea sounds valid and I'd be interested to hear other experienced observers opinions. I also wonder if being under really dark skies makes a difference - I know Tahmoor and it isn't great.
I'm no expert so this may be wrong but years ago I was told that there are two types of dark adaption. The first is the opening of the pupil, that takes only minutes. The second is a chemical change in the retina which increases its sensitivity. I was told that that takes about 1 minute for every year of age. So us old fearts take about an hour to become fully dark adapted whereas young wipper-snappers can be dark adapted in under half an hour. So you need to be more protective of dark adaption as you get older.
There is also an optical illusion with dark adaption but I think it only applies to naked-eye viewing. I used to observe long into the night with nothing more than a faint red light for map reading. I'd then put on some light to pack up and then drive about half a km to the front gate, which I had to get out and open. I'd look up and the sky looked blacker than it did before. I think this was just that I could no longer see the sky glow so clearly and so the space between the stars looked blacker. The other explanation is that
every time I packed up the sky improve within 15 minutes. Hmmm, now perhaps that is plausible.
