Thanks all.
Actually my story is a little complicated. I have a set of Galaxy 18" f/5.5 optics, which I purchased in the 90s (yes - f/5.5, it's not a typo). I followed D.Kriege's notes from the Telescope Making magazine to build my own Dob back then... Kinda didn't work out as planned (I'm an electrical engineer, not a mechanical engineer
).
Now, after a long pause from Astronomy, I am looking at options to return to the hobby. Here's what I am considering:
(a) clean and re-coat both my existing primary & secondary mirrors, then contract SDM to build a lovely scope around them. I have been inspired by claims of 96% reflectivity on Galaxy/OMI primaries, and want in on that action! - I have already contacted SDM.
(b) shelve the 18" f/5.5 optics for now, and just buy a new (& complete) 18" f/4.5 Obsession. - out of interest, I contacted Obsession, but Dave won't take on the "unusual" focal ratio of my optics.
Happy if you want to add to my deliberations...
Cheers.
Mike