Differences in diagonals?

Sometimes I have to wonder how much difference is there really between a generic and well known brand name piece of equipment? Most recently we needed to pick up a new star diagonal, and found they can range between $50 to over $200.00. If all other parts of the optical train are =, will we see a difference comparing a $200 everbright to the $50 mirror diagonal? thank you, Bill

I think one of the bigger differences will be not so much optical quality, but mechanical robustness. A high quality diagonal is usually better collimated and has luxuries such as a compression ring. When I moved from a cheap 2" diagonal to a William Optics 2", I did notice an improvement in overall image sharpness.

In addition to the previous responses, paying the higher prices gets you very little sample error. I've never owned or hear of a bad Televue, William Optics, or Astrophysics diagonal.

However, I've owned Meade and Celestron diagonals (always come with the scope) that were good and I've gotten them that were really bad. One Meade diagonal was so poorly collimated that as you rotated the diagonal (scope on a GEM mount) stars in the center of the FOV would move out of the FOV and then back in again depending on position. I owned a Celestron diagonal that made in defocused stars elongage as if the scope was horribly out of collimation.

In the same breath I've owned those branded diagonals that were very good samples.

How come none of these responses are speaking directly to the optical quality of the diagonal mirror itself? In newt-land, opinions (and facts too) are overwhelming in suggesting that a 1/20th wave diagonal is better than cheap diagonal. Not mechanically, but OPTICALLY. 100% of the light from your telescope whether Cat, Refractor, or Newt, ALL of the light hits that last diagonal mirror, so it better not be the weakest link in the chain, donthcyathink?

TomL

I've always had a Celestron Prism diagonal, and about two years ago I got a standard Televue mirror diagonal and a very cheap $25 Apogee mirror diagonal.

I tested each on the planets in my 4" Vixen APO. I couldn't see any difference between, though the Televue one was obviously the more solid, better looking one, and so won the permanent spot on the Vixen.
Renato