I guess I'd need to chime in here too, because I have now bought a TS version of this F/11 refractor.
I was looking this kind of parallel visual setup to my existing TMB 152/1200 (LZOS) APO and I did not want to put too much financials for such scope, because I know I won't use it as my primary scope anyway. (I'm sort of torn apart between my imaging and visual observing needs and wishes here.) This TS-Optics 102 mm f/11 ED seemed to fit to this dual need here quite perfectly. In short, do I like this ED refractor as my secondary scope? Yes, I do!
This ED model seems to tick all boxes listed below:
* Decent size and light weigth 4" refractor to compliment my current 6" TMB scope (it actually seems to fit quite perfectly on my TMB's piggy-bag setup :-)
* Good image quality (excellent when considering its' price tag).
* Much better RAP focuser compared to average Chinese Crayford focusers seen in most cheapish ED scopes.
* F/11 gives best visuals for any eyepieces you throw to it. Flat and sharp to the edge visual fields are easily focused to pinpoint stars with my EPs.
* Ability to remove that extension for binoviewer usage (yeah, I will put there later M68 extensions and Baader ClickLock 2" visual back as replacement as suggested by Astro-Jensen).
As you can see from the linked image above, I have switched the standard Vixen dovetail to Losmandy one there, which makes this setup rock solid on top of my AP 1200 GTO mount. Both scopes point now to the same spot in the sky, so I can take a visual look from some night sky target very easily with this 4" ED scope and then I can document the same target with my 6" TMB + ZWO ASI183MM camera with only minor adjustments to star field alignment. Right now I don't have any filter wheel to my ASI183MM, but I have a pending order for such from FLO in UK. Anyway, it's really nice to have two scopes pointing to the same spot at the sky and have one designated for astrophotography another for visual observations, when such need comes. For example I managed to split Delta Cygni (a 2" binary called Fawaris) visually with this 4" ED scope (easy split with 234x) and then document the same binary as an image seen here (a B&W image only due to missing filter wheel here at this stage).
Thanks for all previous participants in this message thread.
Your information given here has been quite valuable for myself. For example the necessary modification needs given there were appreciated, likewise the optical tests seen here (I can verify that kind of optical quality from my ED scope too).
For the record and additional information; this TS version of the F/11 ED scope does NOT seem to have such great pitch-black optics coatings anymore as referred in the beginning of this thread. Nor it does NOT have individual serial numbering in place anymore. Otherwise the scope quality seems to be exactly the same as described in this thread (with all good and bad parts there). This is a very balanced 4" ED scope at its' own price point and I'd recommend it to visual observations without any hesitation, at least to such usage where its' specs are best suited.
It you like to see some unpacking images from this ED scope, then those can be found here.