Baader T2 (32mm) Prism Diagonal (Updated: 2/2/15)

Recently I became aware that prism diagonals can perform better than a mirror prism for certain subjects such as planets or low-contrast subjects such as the sun in H-alpha. Hence I decided to get the small Baader T2 prism diagonal, which comes with a 1.25″ focusing eyepiece holder (with T2 threads) and a T2 – 1.25″ nose piece from www.amazon.co.uk

The diagonal came well packaged. It looks solidly constructed, and is actually fairly small – more the size of a 1.25″ diagonal, and not very heavy.

Baader T2 32mm Prism Diagonal
Baader T2 32mm Prism Diagonal

This kit is particularly worthwhile, as the two components attached to the prism diagonal would normally cost well over £50 on their own, and this prism diagonal normally costs over £80 – Amazon has this kit for £86.00.

Baader T2 32mm Prism Diagonal with accessories
Baader T2 32mm Prism Diagonal with accessories
Comes with 1.25"-T2 nosepiece adapter + 1.25" accurate focusing T2 adapter
Comes with 1.25″-T2 nosepiece adapter + 1.25″ accurate focusing T2 adapter

It comes with T2 threads on both ends – male on the eyepiece side and female T2 threads on the scope end. This allows for many different T2 adapters to be used on it. It weighs about 130g just for the diagonal.

Weight of Baader T2 prism is 131g
Weight of Baader T2 prism is 131g
T2 Prism diagonal with 32mm clear aperture
T2 Prism diagonal with 32mm clear aperture

I have mounted this prism diagonal on my Daystar Quark, as I am hoping to use it for solar viewing – and perhaps planetary viewing at a later date. As you can see, the Diagonal is not particularly large when fitted on the Daystar Quark’s T2 adapter. The effective optical path length is said to be only 37mm, so will allow for binoviewers to be used on refractors with shorter backfocus distance.

Diagonal mounted onto the Daystar Quark
Diagonal mounted onto the Daystar Quark

The 1.25″ twist focus eyepiece holder can be adjusted for fine focus (5mm focus travel), and locked in place when the focus is achieved by using the fixing screw. Very useful indeed.

With 1.25" focusing adapter extended fully (has locking screw for accurate setting of focus)
With 1.25″ focusing adapter extended fully (has locking screw for accurate setting of focus)

Having looked through at Mars using my Wiliam Optics Dielectric mirror on the Skwatcher ED80 refractor recently, I did notice that the image was not particularly clear with significant scatter. I am hoping that it will look much better through this prism diagonal.

The main reason for this diagonal being much less costly than the Zeiss prism diagonals from Baader, is that it has the smallest prism (32mm) and uses a Baader Prism rather than one from Carl Zeiss. But bear in mind the T2 Zeiss prism diagonal has a 34mm Zeiss prism and nearly costs double of this diagonal, and the 2″ Zeiss prism is more than double the price of the T2 Zeiss diagonal and is heavy at over 600g, and hence it makes sense that this Baader 32mm Prism diagonal is likely the best bang-for-buck prism diagonal to be had currently. And I will be able to use the Baader Maxbright binoviewer with it, should I decide that I would like to do binoviewing in the future.

Daystar Quark mounted with Baader T2 32mm Prism diagonal and Televue 25mm Plossl
Daystar Quark mounted with Baader T2 32mm Prism diagonal and Televue 25mm Plossl

(Update 2/12/15: Having taken my solar setup for viewing the sun, there was a small window when the sky was clear and I could see the details of the sun. I have to say that using the Baader T2 prism has been a real eye opener, as I have not seen the granularity of the chromosphere that clearly before. And it was now possible to tell when the seeing was better, as everything looks so clear. I have to say that it is definitely much better than my respectable William Optics 2″ carbon fibre Dielectric mirror diagonal. Definitely highly recommended for H-alpha solar visual work.)

Boon