Best size dovetail bars?

[swag72]

I am looking at replacing my current dovetail as well as getting another and I'm not sure what size would be best.

I want one for my SW 120ED Pro to sit on my HEQ5. For that I was planning on getting a 250mm length from Altair Astro.

Then I am looking at piggy backing my Pentax 75 ontop of the 120ED. It already has scope rings, but I thought I'd get a 180mm dovetail to sit on the scope rings of the 120ED.

Woud these be the right sizes or would you recommend something else?

[Merlin66]

That set-up sounds like it would work OK.

The only other option is to consider using the wider Losmandy dovetail ( and a new Vixen/Losmandy saddle) to support the OTA.....

[MjrTom]

I can vouch for the quality of the ADM dovetails.

I started off using the 11" one but upgraded to the 13 inch one to help with rebalancing heavy eyepieces or a DSLR with my 102mm f/10 Achromat.