Dovetail question

[Franklin]

Hi, I'm asking if anyone knows if a certain type of dovetail bar is available and if so, from where?

I'm talking about the synta vixen-style bars that come in three sizes. Short 150mm, medium 210mm and  long 330mm. The short bar has notches cut into it for the locking bolt and safety thumbscrew to engage in. This I think is a much more solid connection of mount head to dovetail bar. My question is this: Is it possible to get hold of a longer bar that has the same design as the short bar with the notches? Thanks.

[johninderby]

Many people replace it with proper dovetail that allows you to slide it back and forth inte saddle to help balance the scope. it’s also common to replace the stock saddle with a clamping type.

https://www.firstlightoptics.com/adm-vixen-type-v-series/adm-vixen-style-universal-dovetail-bars.html

Edited September 13, 2020 by johninderby

[Franklin]

Yes, the ADM products seem very good quality. The spring loaded twin bolt clamps look bombproof. But I'm afraid I'm a stargazer on a budget and cannot afford these wonderful upgrades. I have a skywatcher 330mm bar so I guess I will probably drill an angled hole in the side of it and replace the safety thumbscrew on the mount with a longer one. So as least the thumbscrew will enter the bar by 5mm or so, which would prevent the bar from slipping out should the locking bolt work loose. 

[johninderby]

As far as I know no one seems  to do a longer version of that dovetail now. What you can  do is  use a bolt at each end of the dovetail to stop it ro sipping out

[Franklin]

Good idea, didn't think of that. Thanks.

[Alan64]

Yes, like this...

Any that are within the bar must be counter-sunk.

[Waldemar]

6 hours ago, Alan64 said:

Yes, like this...

Any that are within the bar must be counter-sunk.

In a setup like this you would get less flexure (more rigidity) by using a third scopering or use the places the furthest apart

[Alan64]

27 minutes ago, Waldemar said:

In a setup like this you would get less flexure (more rigidity) by using a third scopering or use the places the furthest apart

The rings are holding a 90mm f/10 achromat within that image.  In so far as the spacing between the rings, they must also accommodate a shorter, 80mm f/6 achromat to which the rings originally belong; two telescopes, one set of rings.  Imagine my delight when I discovered that the one set of rings also fit the 90mm f/10.  

In so far as the bar's length, that's to balance the 80mm f/6 when using a 2" diagonal and a 2" ocular, to move it farther forward.

In that I did not purchase a set of rings and a dovetail-bar for the 90mm f/10, I can assure you that I will not be purchasing an extra set of rings for a third, then to have a useless spare on hand.  For one,  I'm a visual observer only, albeit with the odd afocal-shot taken with a small point-and-shoot camera, but only to demonstrate what may be seen during a live view, through this eyepiece and that, and this telescope and that.  Two rings per telescope, maximum, in my stable, or sometimes for two, if I can get away with it.

I don't even have premium rings for my premium refractor...

...as they are not necessary.  Those work, and serve, admirably. 

Then, what does all of this have to do with securing a telescope within its mount's saddle?