help with attaching vixen as a guide scope

[stafford_stargazer]

I am receiving a vixen 70mm a70lf refractor tomorrow,my idea was to attach it to my 200p dob.

My questions are would this be of any serious benefit?

And if its a worthy idea how and what do i need.

Vixen has rings and dovetail,and i got some 8inch rings coming tomorrow too hopefully.

How to i couple them and how do i adjust the alignment?

Thanks Gary

[RobH]

I can't help as regards the mechanics of how to attach to your particular scope, but a thing not realised by many, is that for imaging, the guidescope doesn't need to be exactly aligned with the main scope.

Using guidescope rings can give rise to differential flexure, so with my system, I don't use them.

I use normal scope rings and have the guidescope clamped to the main scope like a limpet, with no possibility of any movement.

It doesn't point to exactly the same spot as the main scope, but this makes no difference at all when guiding.

Cheers

Rob

[Psychobilly]

Gary ...

Did you mean as a finder rather than a guide scope on the Dob...

For it to be useful as a finder you will have to use adjustable rings or some other method of aligning the two scopes...

Rob...

The Synguider needs you to center a guide star in its FOV (or at least get it pretty close) so if you dont want to alter the framing of the imaging scope you have to move the guide scope to center the guide star..

More testing when the skies get darker...

Peter...

[The Sailor]

I have a 60x700 as a guide scope, changed it over with the finder scope, centered the target in the main and used the ring adjusters to fix the guide scope to same traget. Hope I done that right, if not someone will let me know, I hope

Jim

[Psychobilly]

Yep thats about it ... you can start of with a distant terrestrial target to get it somewhere close but theres no substitute for a final tweak on a Celestial one...

I'd be inclined to keep a cheap RDF on there as well for the initial pointing...

Peter..

[RobH]

The Synguider needs you to center a guide star in its FOV (or at least get it pretty close) so if you dont want to alter the framing of the imaging scope you have to move the guide scope to center the guide star..

Peter...

Think I'll stick with my DSI pro then, as it doesn't matter at all where the star is on the chip.

A guider that requires the guidestar to be centred sounds like a step backwards to me

Cheers

Rob

[Cornelius Varley]

I am receiving a vixen 70mm a70lf refractor tomorrow,my idea was to attach it to my 200p dob.

My questions are would this be of any serious benefit?

And if its a worthy idea how and what do i need.

Vixen has rings and dovetail,and i got some 8inch rings coming tomorrow too hopefully.

How to i couple them and how do i adjust the alignment?

Thanks Gary

Guidescope or finderscope ?. Guidescopes are used for guiding the main telescope during deep sky imaging so I guess you mean finderscope. As a finderscope the telescope may give too great a magnification to be of any use, most refractor type finders have a magnification of about 8x - 10x. To attach the Vixen to the other telescope you would bolt the vixen rings onto the 8" rings, either directly or by bolting a flat metal bar to the 8" rings and then attaching the vixen rings to the bar. You could replace the vixen rings with proper guidescope rings similar to these ST75 5" guidescope rings which would allow you to independantly align the vixen ota. The problem with adding an extra telescope to the 8" ota will be the weight of the vixen causing the main telescope to be heavy at the top so you would need weights at the bottom of the tube to compensate.

Peter

[rawhead]

...I use normal scope rings and have the guidescope clamped to the main scope like a limpet, with no possibility of any movement...

Can you always find a guidestar using this technique?

Do you think it would work using an ST80 and a mono DMK 21AU04?

Cheers

Jon