Ralph Hertle wrote:

Are reticles possible for say 10" Newtonian reflecting telescopes that
would enable angular measurements to be made?

You can get eyepieces with reticles in either 1.25" or 2" format. For
example the first of a great many hits I got on Googling was

http://www.buytelescopes.com/product_list.asp?t=40.

--
Odysseus