Dovetail Flexure

[davelrkn]

Hi Everyone

I have a EQ6 Pro and decided that the standard dovetail that was supplied with the mount was not strong enough and was causing to much flexure to the OTA and was the weak link in a very stable mount.It is well documented over the net on different forums of this problem with the EQ6 mount and have looked at different suggestions and mods that have been put forward.

I have looked at different ways to find a solution that would be fairly easy to achieve and not take a lot of effort.

I purchased a William Optics long type (Vixen Style) which is very solid and paid around $90 AUD and may sound hefty in price as well but feel well worth the money considering the overall price of the mount.

It was very easy to adapt as the two main bolts I used were 50mm x 1/4 and screwed straight into the dovetail both ends as they were the same thread as the dovetail.I made sure the bolts went through the full thickness of the dovetail as the front would then act as a safey in case the OTA ever slipped.

The dovetail comes with a number of pre-drilled holes and it just happened that without to much effort I could then add extra support by using four more bolts 38mmx 1/4 one on each corner to stabilize the OTA even further.It is inportant here to note that these four supportng bolts are not adjusted to thightly as they will push the tube rings slightly away at thier base where the two main bolts pass through on the dovetail resulting in some flexure to return.They should only be adjusted enough to add the extra support to the tube rings to stabilize the OTA.It was at this stage that the only drilling that I did was to drill four small location points on the tube rings so that the four 38mm bolts had something to grip against.The whole exercise took me about 20minutes to complete.

The reason I wanted to stabilize my OTA was for imaging and felt the suppied dovetail was just not up to standard and although this mod was done for my EQ6 Pro the William Optics dovetail does suit a lot of other mounts like Celestron or any mount that has a Vixen style dovetail,maybe also adapted in this manner.

William Optics Web Site has a list of Mounts that suit their dovetails

ttp://www.williamoptics.com/accessories/accessories_mounting.php

Though I would share this with the forum as it maybe of some help to those that may have an issue with dovetail flexure.

Cheers

Dave

[barkis]

Flexure is a big headache, and not always easily eradicated.

One area which you have Identified, is where the tube rings attach to the dovetail. That footprint is too small in area. I hope your additional four support bolts do the job for you. I thought at first you had drilled and tapped the the rings to take the bolts, but that probably would not have been a good Idea anyway. May have led to the rings fracturing at the holes eventually.

Probably a good solution, would be custom made dovetails with inbuilt saddles for different tube diameters. Probably extending to half the tube tube diameter, and hinged keepers to draw the tube into the saddle when screwed down.

These specials would be expensive, but the discerning imager, having spent hundreds of pounds already, (And the rest I hear most saying ) would no doubt go to this length to ensure no flexure of the OTA.

Anyway Dave, I hope yours is successful.

Ron.

[davelrkn]

Hi Ron

l agree with you that is vertually impossible to completly remove flexure but for those of use that don't have a workshop and limited tools, can do something to improve on what we have has to be a plus.The mod that I have done has made such a huge difference .was worth the effort.

With flexure I remember a number of years ago a club member who is a fitter and turner stating that he had measured flexure in a piece of steel 6'' long and 6'' in diameter.

Thanks for your reply

Cheers

Dave

[Psychobilly]

You could consider using Chemical metal to mould some saddles...if you fixed a length of studding into it whilst it hardens they could be fixed to the slots in the dovetail using nuts...

A Piece of tape could be used to stop it sticking to the OTA...

Billy...