tools for checking vigneting on refractors

you asked for it, I used Google 5 minutes to find what helps anybody of you , here we go

such instructions are so easy geometrie , that usual no teaching is needet.

you have a lens diameter and you have at a specific distance a focal point. Make a straight line by your eye or whatever from lens edge to focualpoint. If something is in the way , like knife edge baffle or drawtube, then you have a stopped down aperture.

Now if you want a imaging scope and many manufactors claim here scopes are imaging scope, then you want a 100% unvigneted FOV at that focal point of a specific image cricle diameter. Lets say 35 mm image cricle.

Now the straight line from lens cell edge to image cricle edge shall not be iinterupted by anything like focuser drawtube or knife edge baffle.

Its so easy, that I do not even understand that such a question can come up , its ssimplest school geeometrie.



here is a sheme drawing, if that would be used by the chinese makers we would have no stopped down refractor telescopes

http://www.avgoe.de/astro/Teil02/sv3703710.jpg


here a very nice simple webside , read and check your scope that way

http://www.berfield.com/baffles.html

very best wishes
Markus

Thanks for the tip Markus...
I'll double check my WO SD66... interested in KNOWING...
(I'll post my findings tomorrow, as tonight I'm working late...)


Clear skies, and unvignetted scopes! 8)