Diagonal Comparisons

I'm historically a reflector guy and am dabbling in refractors. I have 0 feel for quality of acessories like a diagonal. I've been searching the threads for something like this but am coming up empty. Has anyone done a diagonal comparison? Does anyone have thoughts on typical ranking/rating of the obvious suspects? Thoughts on standard vs dialectric vs nubright?

I saw the WO review. I'm looking for something like this but a bit wider view.

AP or Televue with dielectric coatings if you want a very good one. Either of these would be excellent, which ever you can afford.

I've tested a bunch of the TeleVue Enhanced and Everbright
2" diagonals. All were pretty good optically. One (out of 6)
was machined too small and would not accept all 2" eyepieces.
The difference between Enhanced and Everbright is supposed to
be something like 5% in brightness, but in practice the
difference will be very subtle.

Astrophysics are also OK. The height of the two inch
inlet is lower, which can give you more effective infocus
(advantage), but some Barlows will bottom out on the mirror
doing damage (disadvantage). Done this myself and seen
a bunch of others like it. Sometimes at 3 AM you've got
four 1.25" adapters and six Barlows out, and suddenly forget
which of the 24 combinations hit the mirror.

I've seen one Dielectric diagonal from top maker with
warped mirror, so probably good idea to test out whatever
you buy. You'd think the quality control would be 100%
on the most expensive ones, but apparently its not.

AP website indicates the largest difference between
Enhanced and Dielectric is durability. But I've never had
trouble with the Enhanced. Maybe the Dielectric coating last
70 years instead of 30 years -- does that really matter?
Not sure its a key factor for most people.

I've had 4 AP Maxbrights, 3 of the Televues, several rather generic Celestrons and 3 Intes, all 2".

The APs are well put together and have a great "feel" to me. The Televues were a slight step down in that regard. The Intes another step lower and the Celestrons "servicable".

There were various level of mis-alignments when using a Glatter laser. 3 out of 4 of the APs were spot on, as were all of the Intes, 1 of the TV and 1 of the Celestrons. All others were sligthly mis-aligned but I don't think that matters too much as I could get all of them out of alignment with the scopes optical axis by simple moving them around a bit in the focuser.

Optically there were no dramtic differences between any of them except I felt 2 of the Celestron diagonals were not QUITE as sharp as the AP or Intes which subjectively were the top of the heap optically. An interesting side note for the Intes is that the coatings seemed to add a very slight/subtle yellow tint which worked very well with my achromats.

Based upon which ones I've kept I'd rank the APs and Intes as equals and on top. I sold the TV's as the Intes were just as good but cheaper on the used market.

Hope this helps.

I've had several 1.25" diagonals, all imported, including one TV, and all were way out of collimation. In fairness to Televue, that particular diagonal was the same as sold by other vendors, so I wouldn't consider it to be "true" TV.

I also had a 2" standard WO diagonal a few years back that someone in the QC department forgot to check because the barrel nearly fell off due to the set screws not being tightened at the factory. Since that same problem occurred to numerous others and was widely reported on various forums, I'm pretty sure WO has taken steps to alleviate that problem on their current diagonals. However, after reassembling the diagonal and making sure the set screw holding the barrel to the body was tightened, I sold it and bought a Stellarvue 2" dielectric diagonal. I now have three of the Stellarvue 2" dielectric diagonals and one Stellarvue 1.25" dielectric diagonal. All are spot-on collimation-wise, and very well machined and assembled.

Jim