Big Bertha: Continued
I did another star party this evening, at an elementary school this time. My, what little...energetic creatures...2nd to 4th grade boys can be. Girls that age are so much better behaved. Still, there were a lot of well-behaved kids genuinely excited by looking at Saturn and the Moon. The junior high I worked last Saturday has kids old enough to have something more than, "Isn't that cool?" conversations, but at this age, just getting them to see something beyond their own horizons is enough.
When I came home, I replaced the too weak (12 pound) springs on Big Bertha's mirror cell with some 28 pound springs--much improved. There's still some work to be done on collimation, perhaps cleaning the mirror again, and center dotting it, to improve the precision of the collimation, but it is only a little disappointing on image. At 222x, the Moon is still a bit soft; Saturn is definitely disappointing. But I noticed that Saturn was going in and and out focus--this may be a mirror cooling issue still. My mirror cell lacks sufficient ventilation for cooling; it is probably time to cut some cooling (and lightening) holes in the cell.
Anyway, some readers wanted to see this beast, having some trouble imagining it.
You can see why I take the 5" refractor to star parties.