Dovetail Rails?

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Hi everyone,

Designing a dovetail-to-NATO adapter to mount a red-dot finder on my girlfriend's Skywatcher Dobson, I got a bit confused by all the different dovetail rail descriptions I found online.

I ended up using a 32.5 mm base, 10 mm height, 60 degrees flank angle.

While this works, it's evident that the dovetail shoe on the telescope is designed for feet of 34 mm at least.

This site is a source of a number of good and some not so good drawings, and of some helpful and some rather confusing descriptions:


I presume the pictured shoe is the one used on my girlfriend's telescope, though hers actually has a cut-out that would work great to prevent inadvertent dropping of the finder, if it weren't mounted on the downward side.

If anyone could help me with the official name of that shoe, or system, that would be great!

While it's obviously called "FB" by Stellarvue, it seems to be designed for "F2" components, or "F2E", according to other product links. Stellarvue also seems to be fine with multi-millimeter gaps between shoe and foot, so I wonder ... is my 32.5 mm foot within specifications?

The background is, I'd of course like to get the description of the Dovetail-to-NATO adapter right for uploading, and at the moment, I'm really badly confused about astro dovetail rails.

Many thanks in advance for your help!