Dovetail size

[MattT]

Hi,
It's raining in Melbourne again and I have a question on Dovetail length. Is there any difference using a 200mm or 300mm length dovetail? I'm not any kind of engineer at all and wonder why my 200mm newt came with these two dovetails. :question:
In anticipation... Matt

[bmitchell82]

it more depends on your tube, if you use a short dovetail then it allows your tube to flex (or for better words droop) because your holding it very close together. Its all a case of equilibrium, moments and forces.

The further you spread the rings apart the lower the forces become, which in turn gives you less flex.

My 254 newt has the dovetail at 300mm, and the top plate at 400mm with the rings at the end of the top plate. I have done analysis on flexure of dovetails and to be honest there is bugger all.

If you haven't upgraded to a Losmandy D saddle and dovetail yet though I do suggest that you do because they are a lot better system.

Brendan