In my reckoning there has always been a few toggles about the project. Never considered 'inexpensive'.
The Matsumoto EMS have always been a given. Engineering wise I can't think of a more elegant solution. Going at todays exchange rate we are just above $4k usd for the large pair with bells and whistles? Only toggle there is size, and that affects overall cost all depending which scopes I use.
Another toggle is ability to use stock scope focuser(s), and OTA's including dew shield(s).
Then the OTA / optics cost which in my case here is a big toggle after looking through the optic as I like to see for myself. The main reason I can rationalize is that there is a benefit to using higher magnification yet still below typical seeing limit, with a reasonably large exit pupil (for a refractor under 8"). An example here is that neither my 128 or my 150 will can function at highest mag's possible my seeing here. On my scope spreadsheets, I have a column I call experimental telescope working function. It's an odd sort of formula based in the scopes eyepiece mag(with a given ep focal length)/per inch aperture divided by quantity 'exit pupil div by scope tFOV (at given ep parameters)'. In any scope the higher this number the harder the overall optic working wrt its own design and the atmosphere or seeing. Another way to express is the obvious the better the seeing the higher the power or twf limit.
Translating the above, typical better seeing here might support a 5mm eyepiece, rarely anything shorter. With the SW 150 that put's me at 0.625 exit pupil with a 5mm eyepiece, so I'm not in the sub 0.5 exit pupil dropoff. A 6mm eyepiece gives a 0.725 exit pupil. And it just gets better as the eyepiece focal length increases. With a 6mm eyepiece I am operation below the 200x sky mag OR 50x/inch caution zone and then everything (atm or optical) nowhere near it's design edge (that includes my typical atmospherics). To me the scope working function a sort of triple check against unrealistic expectations.
This keeps my OTA costs under $4.5k usd for what I consider very acceptable viewing quality at the aperture. The additional light grasp (though compared to mirrors per cost) is still 'small potato's' but the added near inch per OTA to me is meaningful.
Then the cost of mounting. I'm making my own with some help, and no idea what cost will be until it's completed, and if I include RA 'tracking'. Overall weight I hope to keep at, near, or under 50 lbs. I know mounting not free so add more $ here.
There is also additional cost in needing eyepiece pairs, this like the EMS more a constant or given as far as additional $$$.
Just wanting to cover all the bases.
"How to go from one 150mm f/8 doublet scope to equivalent binoscope for $10k or less."
Edited by CounterWeight, 22 May 2019 - 10:54 PM.