View Full Version here: : Best 1.25" prism diagonal

The Mekon
15-08-2017, 05:59 PM
The title says it all. Which one is the best? No I do not want a Takahashi as I would be forever figuring out ways to join it to the optical train.

William Optics?

what is the best value for money?

15-08-2017, 06:22 PM
The best is the Baader Zeiss T2 prism with the BBHS (broadband hard silver) coating.. but it is also one of the most expensive

Full T2 compatibility, very low scatter, shows colours of stars well...

15-08-2017, 06:24 PM
Hi John,

I hope you are enjoying the views through your new refractor.

CFF recommends prism diagonals for their telescopes, unless one has their scope tuned for visual, which must be specifically requested at the time of making an order. Here is an interesting article about diagonals: http://www.baader-planetarium.de/news/mirror-Prism-Dielectric-Diagonal-Comparison_2014-03-06_v2.pdf

MaxBright (mirror diagonal) has very good reviews as far as I know.

15-08-2017, 07:13 PM
Have to agree on that one....and perfect for pairing with Binoviewers :thumbsup:

15-08-2017, 08:31 PM
That's tongue in cheek I assume (I hope, since it does just have a 1.25" nosepiece like every other - I use mine in my Esprit 80 and Star 12ED a LOT).

Baader is apparently the best, followed by Tak 1.25. Vixen one is REALLY carp, and never heard a good thing about the WO prism (yellow inclusion etc).

15-08-2017, 10:03 PM
Reckon you'll discover a mirror star diagonal is better. But you already knew that, right ?

15-08-2017, 10:43 PM
If you likescatter, sure.

Prisms are recommended for refractors above f/6.4

The Mekon
16-08-2017, 07:29 AM
Matt, the T2 cannot be a 1.25' with a T2 thread. We might be getting a bit mixed up here as it is a mirror if it has silver coating. I am mostly interested in prisms.

This thought has come to me as I struggle with my UO 2" prism which is excellent optically - much better than a Bintel 99% dielectric that I have but not so good to work with mechanically. There seems to be a dearth of 1.25" prisms on offer. I will probably end up buying a Baader 2" dielectric with the clicklock, but thought first about a 1.25" prism which could also be used in my smaller scopes.
The ultimate solution is the Baader 2" zeiss prism which I think is over 400 euros. not sure I want to spend that much.

(and thanks Suavi - I have that article on diagonals that you linked)


The Mekon
16-08-2017, 07:30 AM
I think you are wrong here Wavytone - everything I have seen points to the fact that a well made prism is superior.

16-08-2017, 08:11 AM
John, ..... the Baader T2 Zeiss #2456095 prism actually has a BBHS coated hypotenuse surface, the surface is first coated in silver, then copper before being sealed against any oxidisation.
Their T2 Zeiss and 2" Zeiss prisms have had the BBHS coating for the almost two decades, the use of the coating on the mirrors is only a recent development. Both are available in 1.25 (Actually the prism is slightly oversized at 35mm ) and 2" sizes. I have the smaller prism which has a female T2 thread (42x0.75) on the scope side and a male T2 on the eyepiece side. These can be fitted with either the 1.25" or 2" nosepiece or the Baader Quick Connect coupling.

I use the T2 Zeiss with the 2" nosepiece and the HD Quick Connect for my binoviewing and the 2" BBHS- Sitall mirror for mono viewing.


16-08-2017, 08:11 AM
According to CN aficionados (and Matt) the Baader 2" BBHS mirror diagonal is equal to the best prism diagonals; if you need the best in a 2" that would be my choice.

At 1.25" there's the Baader T2 diagonal with Zeiss prism.

16-08-2017, 10:00 AM
Yes, like Matt says, it's oversized. It is in reality somewhere in between 1.25" and 2" (36mm actually), and can be configured with either size nosepiece.

16-08-2017, 10:03 AM
Just to clarify, the BODY of the Baader 1.25" prism diagonals are OVERSIZED (yet SHORT) to allow fitting of T2 connections. A VERY good idea, as it negates needing to use a 1.25" adaptor in the drawtube.

I THOUGHT I was getting one from Extravision, but they sent a 2" Maxbright instead (T2 fittings). Not complaining, but definitely not 1.25 prism :(