Recently, I was thinking if I should acquire a Borg 125ED to replace my C5.
The logic behind is that, it gives equivalent aperture without central obstruction, it could be used with a Herschel Wedge, and also can be used more effectively for H-alpha imaging with PST etalon module.
However, with a recent discussion in cloudynights, I was reminded that the decision is really on the mount. The C5 can be mounted on the TG-SP II very peacefully, but the Borg is probably too long even if it's not too heavy. So, the Borg 125ED can never replace the C5, a C6 could be.
For this factor, I suppose I will stop looking for a Borg 125ED, for it is not really a good fit. A Borg 101ED could be, however. But in that case, it might not be able to completely replace a C5. And still, my TG-SP II would be a bit hard to handle a Borg 101ED, too.
Time to re-think.