ATM Olympus OM-2 and mirror weights

[Matt Hughes <mhughes@qualcomm.com>]

Hello! 

I hate to start with an off-topic subject, but I was interested in a
thread a while back about cameras for astrophotography. 

I am looking at buying a used 35 mm SLR for both normal terrestrial use
and some astrophotography. Everyone seems to love the Olympus OM-1 for
astrophotography. I was considering buying one, and called a camera store
that was advertising one - turned out it had just been sold. The owner,
however, called back and asked if I would be interested in an OM-2 ...


Knowing not much about the OM-2, can anyone tell me what the major
differences are? (The owner did say the OM-2 uses a battery which is still
in production, vs. the OM-1 which he said you have to play odd tricks
with. This sounds good, but what about mirror lock-up, weight,
exchangeable focus screens, mechanical shutter, etc?) So - does anyone use
an OM-2 for astrophotography?


A second and unrelated question - I'm working on an 8-inch Dob, and I'm
getting to the point where I need to know the approximate balance point of
the OTA in order to start working on the rocker box (need to know side
height). Unfortunately, the mirror I ordered hasn't arrived yet, so I
can't just balance the thing and find out. Can anyone tell me what the
weight of an 8" f/6 mirror is likely to be? Any ideas how to find the
balance point (a big scale would certainly make it easier - oh well). For
an 8-inch, what are the consequences likely to be in just assuming a
pretty bad case, making the rocker box, and then adding counterweights if
necessary? I'm not TOO worried about weight in an 8-inch, but I'm more
concerned about base stability. How high can I get an ~13" square rocker
box before running into problems?
                                        Thanks much for any insight!
                                                        Matt Hughes
                                                 mhughes@qualcomm.com