I wanted to note here my found solution to the Takahashi Epsilon backfocus challenge.

As far as I could find, the backfocus to some sources, is 56.2mm. Although sometime also one can find values like, 56.4mm or 56mm.

Nethertheless with my hardware at hand, filterwheel with an additional OAG (handy / one-box-solution possible / easy storage / etc), whatever I came up with, the solution always surpassed the backfocus length with at least 10mm. It took me a long time to figure out a solution that matched my "all-in-one" telescope... This without all the additional finderscopes, guidescopes, etc etc etc. Overall it would be messy enough anyway, so therefore the "OAG+EFW+Cam" setup.

In the end I came up with the following solution, which gives me, depending on the backfocus length taken: 1.5mm (56.0mm bf) or 1.7mm (56.2mm bf) or 1.9mm (56.4mm bf) adapter space left to fill. Given that a filter adds length to the image train as well, I am guessing I am in the sweetspot now... ;-)

// ---

Would have loved to go with the above, but it seems that with the setup mentioned, the focal range getting in focus with the OAG camera is incredibly short AND inside the OAG. I figured this out by pushing my ZWO ASI120MC-S camera way way inside the OAG midi setup. The connection to make this even happen was too flimsy and unworkable. Therefore choosing the easy way out with the additional guide scope

--- //

-- -- -- -- --

(Pictures A and B)

Stuff shown:

Picture overall:

- Takahashi Espilon 130D

- ZWO ASI071MC Pro (backfocus flange to sensor: 17.5mm)

- Starlight Xpress MIDI Filterwheel 2" with (!) OAG built-in

- Starlight Xpress Lodestar 2, guide camera

Other picture shows the changeable adapter M.. rings, in this case a "M54x0.75 Male"-adapter

The construct from adapter inner flange (telescope facing) to flange ZWO camera = 37.0mm

Given a backfocus of 56.2mm:

--> 56.2 - 17.5 - 37 = 1.7mm space left.

I hope this is useful for people out there struggling with the same "how to" issues/question for this Epsilon scope.

-- -- -- -- --

(Pictures C and D)

Current setup...

Would have loved to have a OAG instead of a guidescope, but this setup works as well:

- ZWO EAF

- Starlight Xpress EFW

- ZWO EAF - Takahashi extention kit

- Astro Essentials 32mm f/4 Mini Guide Scope

- Lodestar X2 camera