My second ponderance in as many days. The science behind spinning mercury mirrors is pretty well know - I believe the largest is the 6 metre one in
University of British Columbia's
Malcolm Knapp Research Forest.
Basically a spinning liquid mirror costs about 1% of a normal mirror of the same size, the downside the primary can only pointed straight up.
Two questions spring to mind - if they snap froze a slowly spinning mirror - that was only just above the freezing point in the first place - could the mirror then be pointed in all directions?
The second question is why don't they just use a second flat mirror placed directly above the spinning primary to capture light from any point in the sky? A flat, non flexing mirror is surely easy to make - and it it was titled at say 45 degrees - reflecting into the primary - then the primary would have a view in that case at 45 degrees. That way you only need to position the flat mirror to reflect into the primary the region you are interested and the spinning mirror would do the rest? Would this design give you the best of both worlds? Maybe even you could put adaptive optics on the flat mirror and make super large telescopes?
Best regards all, Matt
