Diagonal for ed72

[Trentend]

Apologies if this is a daft question, recently purchased an ed72 refractor. Trying to work out if I need a 1.25 or 2inch diagonal. All of my eyepieces are 1.25 inches and also hope to pair with my wo binoviewers. Already have a 2 to 1.25inch self centre adapter. Do I use a 1.25 diagonal in the adapter or just go with a 2inch diagonal?

Thanks

[Stu]

Not a stupid question at all.

A few thoughts....

Do you have an plans to buy a 2” eyepiece? If not, that obviously takes away the real necessity. It depends to a degree what you are using the scope for? If weight is an issue for travelling then the 2” will be bigger and heavier obviously.

I do find that 2” diagonals just feel that bit more solid, probably because of having more area to grip on in the diagonal, and they tend to resist rotation more when using heavy eyepieces. That might be a consideration with your Binoviewers, you don’t want them flopping downwards.

The counter point to that is inwards focus range. Binoviewers need a lot of inwards travel to reach focus, often needing a barlow or GPC to achieve this. A 2” diagonal has a longer optical path than a 1.25”, so would make reaching focus more difficult.

A T2 diagonal may be a middle ground worth considering.

I have a 72mm ED scope and really enjoy it.

[Trentend]

Thanks Stu. No plans to buy any 2 inch eyepieces (just my 24mm pans in the bino) so looks like I can go with a 1.25 diagonal.

[Waldemar]

You can also choose for a T2 diagonal, for example this absolutely top quality piece: https://www.baader-planetarium.com/en/accessories/baader-t-2-bbhs-r-mirror-diagonal.html