Thanks Astro, that's very useful.
At the moment the issue for me is understanding the current product range, and where each sits with regards performance. After that comes price. I feel that the top tier will give exceptional performance at a premium price, while the lower spec'd products will have shortcomings.
If it's anything like pro audio, the top 5% of performance is the most expensive to achieve, so I'm looking for something that will give me excellent performance with no vignetting, but not the best in class.
Here's a quick list of different diagonals:
2" mirror
Baader #01A T-2 Maxbright Mirror Diagonal (Sital-ceramic mirror/140 coating layers), w.male/female T-2 thread / solid metal body $403
Baader bbhs mirror
https://www.ozscopes.com.au/baader-2...clicklock.html
Televue everbrite
https://www.bintel.com.au/product/te...-2-inch-satin/ $495
Bintel quartz
https://www.bintel.com.au/product/bi...2-inch-quartz/ $199
Bintel dielectric
https://www.bintel.com.au/product/bi...ch-dielectric/ $179
Bintel
https://www.bintel.com.au/product/bi...agonal-2-inch/ $109
I'm going to assume the Bintel products are the same as GSO and other generic diagonals around each price point...
2" prism
Baader #01B T-2 Stardiagonal Prism (Zeiss Prism), w.male/female T-2 thread $348 (need accessories to connect)
APM
https://www.apm-telescopes.de/en/opt...adband-coating $404 + shipping
At the moment I'll leave it there (work drags me away), but my thoughts at the moment are that the Baader T-2 zeiss prism looks good. If I'm going to spend at least $200 for a decent mirror diagonal, then the step up to zeiss prism might just be worth $150, although accessories will be needed. I'm sure quality would be excellent though.
Cheers
Stephen