I really like the idea of a flip mirror. They shouldn't be hard to use. Sadly this one comes with no documentation and a confusing set of adapters. The helical focusser was very stiff and it was unclear if it was locked or could be loosened. The mirror unit was larger than I had anticipated and I couldn't reach focus in the straight-through position. A list of contents and some kind of schematic should be provided both online and as a paper copy, otherwise this really is a waste of time.

I needed a device which would hold an eyepiece with illuminated cross-hairs synchronised to a camera on a T2 mount to help with the problem of focusing on the camera's monitor screen. This flip mirror does the job very well, and the sparse website description doesn't reveal how versatile it is. T2 threads are used for all attachments, so the microfocuser can be fitted either at the end or on top of the mirror box. The focuser has two index lines, and the scale can be released and reset against whichever is most conveniently positioned by using a small hex key on two grub screws. Not mentioned in the description are two eyepiece holders; one has a female T2 base. The other has a male T2 base, and its own screw adjustment of about 15mm with a locking thumbscrew. Finally, a female to male T2 adaptor is provided, with a locking ring, so any accessory fitted using this can be locked in the most convenient orientation. Since all threads are T2, T2 extension tubes can be used for further adjustment of clearances. The only aspect which might cause a problem is that the box adds about 75mm of extension, so short tube telescopes might not focus at infinity if a camera on a T2 mount is used. I found this with a Startravel 102mm refractor, but the problem was solved by replacing the standard 2" focuser with an M56 to T2 adaptor; this is shorter than the 2" mount and gave enough additional back focus to allow infinity focusing. The flip mirror certainly gives the impression of having been designed by someone who understands how these things are likely to be used.