Diagonals

[Alien 13]

I have often wondered what is available for people like me that refuse to have their brain messed with with the STD star diagonal, I know the WO is highly thought of for 1.25 inch eyepieces but what about 2 inch. The diagonal must be a 90 degree job and be good at astro targets.

Alan

[Ruud]

It's for the left-right reversed thing, right?

You're out of luck with WO. They currently don't have a 2 inch erecting prism. Just 1.25". See https://williamoptics.com/products/diagonals-erecting-prisms. I'm not sure if they ever had one.

Baader have a 2" model that's popular, but they say it is "not suitable for high magnification - for high quality astronomical images with high magnification using better our mirrors and prisms".  See the link.

WO have good 99% diagonal mirrors. Not that you'll notice much difference with your current diagonal, unless it is really substandard. I got their dielectric on quartz model of a few years back to replace my Telvue enhanced aluminium. The TV had developed a dull spot after 25 years. Dielectric coatings are much more durable. As far as I can tell, optically, the WO is as good as the TV.

I also got a WO 1.25" dielectric mirror diagonal to replace the standard diagonal that came with my 6SE. The Celestron stock diagonal looks slightly milky. It's not too bad, but when you hold it next to the WO you can see a difference.

[Louis D]

I'm pretty sure that if you have enough in/back focus, two normal diagonals placed at 90 degrees to each other will result in an erect, non-reversed image if you view from the side of the scope.  Have the first diagonal send the image sideways to erect left to right and the second diagonal send the image upward, erecting top to bottom.  You do need to look into the second diagonal as if the scope were pointed 90 degrees to the side of where it is pointing which can be a bit awkward to get used to initially.  I'll have to dig it out, but I once made a super compact erect image finder using two 2" right angle surplus prisms cemented at right angles to each other along with a 62mm f/4 surplus objective.  Since there was about 110mm of light path through the prisms, I had less than 140mm of optical distance left to mount the objective and eyepiece ends with some PVC plumbing bits.  It worked stunningly well but weighed well over a pound due to all the glass involved.  US military grade spare optics really rock!  All were still sealed in moisture proof packaging.

If you use two high quality dielectric, silver, or prism diagonals, the light losses should be minimal.  You could try the concept first with two 1.25" diagonals to see if you like it if your refractor has enough in/back focus.  It would certainly work with an SCT or Mak.