Let's be honest. In its current form it is completely impractical and pretty much useless. A good candidate for a faster f/ratio re-figuring. Very well priced though.
Without refiguring, the scope could be made with a concave secondary and a flat tertiary. It might, at that point, be a relatively long f/ratio (perhaps f/20?) planetary scope.
But the secondary would be too large for planetary contrast with that configuration.
I agree it should be refigured into something much shorter.
Assuming the glass is decent, regrinding to, perhaps, an f/5 length would be able to use a small secondary (under 20%) and be superb for planetary and lunar work.
and not too shabby on DSOs, either.
