Do I need a dovetail?

[stephec]

I have a 150/f5 reflector which is currently mounted with the scope rings directly to the mount, would there be any advantage to using a longer dovetail instead? 

 

[Mandy D]

Definitely. If you use a dovetail and quick release clamp, it will be very easy to balance your scope when you change accessories.

[stephec]

Thanks Mandy, I was hoping someone would say that as I like the look of the Skywatcher green ones. 😅

 

I don't know anything about quick release though? 

[Mandy D]

1 minute ago, stephec said:

Thanks Mandy, I was hoping someone would say that as I like the look of the Skywatcher green ones. 😅

 

I don't know anything about quick release though? 

You need a saddle to clamp onto the dovetail. Quick release was probably the incorect term that my covid-addled brain came up with. I use this one from RVO.

https://www.rothervalleyoptics.co.uk/rvo-mini-vixen-style-clamp.html

I find it works very well and you don't damage the dovetail because the screws do not bear down directly on it. I have the green Skywatcher dovetail on my 200P and it works very well with this clamp.

[vlaiv]

5 minutes ago, stephec said:

I don't know anything about quick release though? 

Your mount does not have vixen type clamp, but you could possibly fit one to it.

For example this:

https://www.firstlightoptics.com/dovetails-saddles-clamps/astro-essentials-mini-vixen-style-dovetail-clamp.html
 

if you can unscrew current piece for telescope attachment (it looks like it is held by single bolt in the middle) - then you could possibly use the same bolt to attach vixen clamp instead of it.

There are also bigger versions that are more sturdy but also more expensive:

https://www.firstlightoptics.com/dovetails-saddles-clamps/william-optics-90mm-saddle-plate-for-vixen-style-dovetail-rails.html

[Mandy D]

Expanding on what Vlaid has said, I think the centre bolt will foul the dovetail with most clamps using that method. I had not noticed that the mounting plate was not flat. I would pick up on the two end holes, put a stack of washers over them and bolt a piece of 6 mm or thicker plate to it that clears the obstruction and bolt it down. The clamp can then be bolted to the centre of the piece of plate. Drill and tap if you can, or just use cap head screws and nuts. It will make better sense when you have all the bits in front of you.

[stephec]

A couple more photos, I've taken off the top 16mm (seriously, who uses 16mm?) nut and the two cap head screws on the side, but the top section won't budge, it looks like it contains the slow motion gearing. 

 

It looks like Mandy's idea is the one, and luckily I work for an engineering company so it should be no problem to get hold of a piece of 6mm SS bar cut to length, an M8 countersink screw in each end with a few nuts on it to raise the bar to the right height, then a couple of holes near the centre to mount the clamp. 

 

It might look a bit like something the A-Team would make but it's still cheaper than a new mount. 😅

 

[John]

This is a company in the USA who market a dovetail clamp arrangement for EQ3 mounts that don't have one. I don't suggest you buy one but it might give you something that you could copy yourself:

ScopeStuff

[ollypenrice]

You can balance the scope at present just by sliding it through the rings. If that gives you enough range, well, it just does!

The saddleplate-dovetail allows the scope to be removed a little more quickly and the rings come off with the tube. Depending on how you set up and tear down, this might be useful or might be a way of spending money for no substantial benefit.

If were using this scope in an observatory, for instance, I wouldn't bother.

Be aware, also, that the dovetail rail should have stop bolts at both ends to stop it sliding through the dovetail clamp. This is a classic way to trash a telescope!

Olly

Edited October 5, 2023 by ollypenrice

[stephec]

41 minutes ago, John said:

This is a company in the USA who market a dovetail clamp arrangement for EQ3 mounts that don't have one. I don't suggest you buy one but it might give you something that you could copy yourself:

ScopeStuff

I like that, at work we use a man made wood called trespa, I could probably get a block cut to that size and drill and tap it as needed. 

[stephec]

35 minutes ago, ollypenrice said:

 

Be aware, also, that the dovetail rail should have stop bolts at both ends to stop it sliding through the dovetail clamp. This is a classic way to trash a telescope!

Olly

Why have I got the Benny Hill theme tune playing in my head? 😂

 

That does explain what the bolts in the end of the plate that I looked at earlier are for though.