All I can add to Eddgie's comments is that a 6" mak will be tough to cool in a reasonable amount of time, particularly in your northern climate.
If you do go to a mak...
If you go that route I'd look for a Sital (on the Intes or Intes Micro) or other low expansion mirror. Mine was rough to use in cold weather.
The Intes are, I think, more common than the Intes Micro, and are also very good indeed. I have heard the Intes Micros were slightly superior, but I think it was mechanically, only. The Intes diagonals and other accessories were very well regarded back when they were around. Mine are very high quality.
I think most Intes shipped at 1/6 wave and some were 1/8 wave, high strehl, but I am not sure. 1/4 wave were also available, and the figures were not imaginary. The MK67/66 Deluxe may have had the better mirrors? Its been a long time but lots of reviews are still online.
They really hold their value on the used market, no surprise there. WTB ads may flush some out.
I gave up on getting an etx even remotely close to the same quality, perhaps a hand selected Terabeam, but good luck (and no coatings), Eddgie is right on on the limited selection.
The Russian maks have a slightly different thread rear cell pitch which might, but not always, cause issues.
The knob focusing versions had virtually no focus shift IIRC. Mine didn't have any I noticed. And don't let the mickey mouse stick on letters on the ota sides scare you off.
A last suggestion from the dark recesses of memory, I think the planet-killers of the era were the mak-newts like the MN series with very small central obstructions.
Lots of Google results for reviews on such old scopes!
+1 on the binoviewers. Wish Baader would pump out some of the new Maxbrights already.
Edited by markb, 31 December 2019 - 04:17 PM.