Well it’s raining (snow due!) so I decided a) to check if my Nikon 800E would fire with exposures over 30seconds with a single usb lead - yes its does. And b) to see what effect not closing the eyepiece blind would have on the field illumination.
Slightly worried by the result:
So no more thinking that its dark outside and those LED’s wont have any effect!
These were taken in normal room lighting so more extreme than you would face under the stars but enough to say that some unevenness could easily be present with long exposure times.
Top pair: blind open (left) blind closed (right)
Bot pair: Blind closed for both one is 2x2 binned(left) 1x1 (right) - no stretching has been done on any of the frames all are taken from screen grabs, cropped to the frame outline and arranged in PS.CS3 Ext.
Right hand frames have cropped on upload sorry