Does anyone else get 77 degrees when measuring an ADM (Vixen mini) dovetail angle?

[MercianDabbler]

Online sources (including ADM) give 75 degrees as the angle of the Vixen style mini dovetail.

I milled my own with a 75 degree angle and it doesn't quite match. I've checked mine and I'm as sure as I can be that I hit the angle correctly.

Measuring an actual piece of ADM dovetail and doing some trig I got an answer of 77 degrees... which would explain why my ADM clamps grip the fat side of the dovetail and have a small gap where the clamp jaw ends.

The clamps grip OK and I doubt I will do anything about it now because my putting metal back on cutter seems to have gone astray... but thought I'd ask.

It would be interesting to know how a proper Vixen one measures up too.

[JeremyS]

I’ve observed a range of angles and also widths in vixen style dovies. Not sure what is “correct” or what the original Vixen spec was. Darned annoying when it doesn’t work out, though!

Edited August 11, 2021 by JeremyS

[MercianDabbler]

2 hours ago, JeremyS said:

I’ve note a range of angles and also widths in vixen style dovies. Not sure what is “correct” or what the original Vixen spec was. Darned annoying when it doesn’t work out, though!

Thanks. Kinda comforting to know that it's not just me then.

I think this was the page that I was using as my original source - it does seem to have been measured by someone who recognises the difficulty of measuring a dovetail so hopefully they did it right.

I also just found a drawing of the Stella Mira bar on the FLO site. That drawing gives an angle of 76 degrees.

I think ADM are probably consistent between their bars and clamps and between clamps bought on different occasions... so it's puzzling that their web site says 75 degrees. Oh well.

[JeremyS]

3 minutes ago, MercianDabbler said:

Thanks. Kinda comforting to know that it's not just me then.

I think this was the page that I was using as my original source - it does seem to have been measured by someone who recognises the difficulty of measuring a dovetail so hopefully they did it right.

I also just found a drawing of the Stella Mira bar on the FLO site. That drawing gives an angle of 76 degrees.

I think ADM are probably consistent between their bars and clamps and between clamps bought on different occasions... so it's puzzling that their web site says 75 degrees. Oh well.

Funny thing is I have a couple of Tak vixen style dovies and the only clamp that doesn’t hold them is an ADM clamp. It won’t close enough - the dovie is too narrow.

[omo]

3 minutes ago, JeremyS said:

Funny thing is I have a couple of Tak vixen style dovies and the only clamp that doesn’t hold them is an ADM clamp. It won’t close enough - the dovie is too narrow.

Its not just the ADM clamp that the Tak dovetail doesn't quite fit, i discovered the same with a Primaluce dual clamp.

Believe me the air turned blue as i watched the Tak begin to slide 🤬

[Robindonne]

I recently bought a used telescope with vixen style dovetail which doesn’t fit my vixen style clamp😬.  The dovetail is too wide to get in, and the front and back are covered by a plate to prevent slipping out of the clamp. So cant use it.  Strange size fluctuations in these bars😏

[John]

1 hour ago, JeremyS said:

Funny thing is I have a couple of Tak vixen style dovies and the only clamp that doesn’t hold them is an ADM clamp. It won’t close enough - the dovie is too narrow.

I bought a brand new William Optics "Vixen type" DT bar a couple of years back which turned out to be a little narrower than the "standard" size, whatever that may be. My ADM clamps didn't hold that one either

Fortunately the supplier was FLO so a return / refund was speedily arranged but I was a bit baffled as to why WO decided to make these bars just a little narrower

 

[johninderby]

Standards do seem to vary by a couple of mm.

I notice that on many Bresser scopes they have a removable plate on one of the dovetail bar sides to accommodate variations in saddle clamp width. 

Edited August 11, 2021 by johninderby

[MercianDabbler]

8 hours ago, John said:

I bought a brand new William Optics "Vixen type" DT bar a couple of years back which turned out to be a little narrower than the "standard" size, whatever that may be.

One would hope that Vixen is the standard... but I think everything I have found so far has been for 'Vixen style' dovetails from other manufacturers.

I hadn't realised there were so many variations. Having some narrower seems particularly problematic.

[Carbon Brush]

As it happens my 'Vixen size' dovetails and clamps all work well enough together for me to not worry.
But if I had fitting issues, I would contact a few of the better quality manufacturers and see what came back.

If it is any consolation, the ADM/Losmandy/whoever big fixings also suffer variation.

When I first used these on my big mount, I had an assortment of rails and clamps from various manufacturers..
Some fitted better than others. Well actually certain combinations of parts did not fit.
Where is the standard? What is correct? Should I mill/file oversize parts? Should I shim undersize parts?

I asked various manufacturers about a standard and only ADM were good enough to send me a drawing of one of their bars.
I uploaded this to SGL in 2013 and have made members aware when fitting issues have been raised.
I regard ADM as the standard - in the absence of replies from other manufacturers.
When buying new, I have chosen ADM parts, rather than other manufacturers.

https://stargazerslounge.com/applications/core/interface/file/attachment.php?id=88097

HTH, David.

[JeremyS]

Rowan probably have a good handle on this. All my vixen dovies fit their clamps perfectly. I suspect they’ve built in a bit more adjustment wiggle room into their clamps.

[Len1257]

1 hour ago, Carbon Brush said:

https://stargazerslounge.com/applications/core/interface/file/attachment.php?id=88097

Except this doesn't seem to be a Vixen Bar?

[Carbon Brush]

@len1257 Except this doesn't seem to be a Vixen Bar?

The drawing is included as an example of the standard of information a helpful manufacturer is able to provide.

Maybe the OP will wish to contact ADM (or others) for dimensions of their 'vixen' parts.

HTH, David.

[johninderby]

1 hour ago, JeremyS said:

Rowan probably have a good handle on this. All my vixen dovies fit their clamps perfectly. I suspect they’ve built in a bit more adjustment wiggle room into their clamps.

The Rowan saddles are higher quality than the ADM. Just much more precisely made and better fit and finish.  Never had any problems with clampling any dovetail I’ve tried. Good old Brotish engineering. 👍🏻

Edited August 12, 2021 by johninderby

[MercianDabbler]

Thanks all. I think the main message is to stick to one brand or else check carefully that clamp A will fit dovetail B. I don't have a big problem with mixed brands - everything I have is either ADM or home made. Just a pity that I did not realise that there was variation in the angle before I cut metal... but it still works.