Guide Scope Mounting

[Robny]

Hi All

Im finaly getting my gear together and have obtained a SW ST80, this is going to be used as a grab and go for the times that I travel but primarily as a guide scope for my SW Quattro S8, this is where my question is. What is the best way to mount the guide scope, there is only two ways I know of, side by side or sat atop of my tube rings. I'm aware that I'll need to purchase some guide scope rings maybe these:?

http://www.firstlightoptics.com/adm-guidescope-rings-and-systems/adm-vixen-style-dovetail-bar-with-guidescope-rings.html

But what are the pro's and cons of both methods and actually from the more experienced what would you recommend for mounting and have I missed any other methods out there?

Many Thanks

Rob

[Andymac79]

I would just use scope rings, I dont think you will have a problem picking up a guide star with the ST as long as your guide camera as good enough. I use a 50mm finder mounted in home made adjustable rings and never have to adjust to find a star, even better with your 80mm

[Psychobilly]

I use a 500/f8 telephoto lens as a guidescope with a Meade DSI IIc and have never had to move the guidescope to get a guidestar...

Peter...

Sent from my GT-P7300 using Tapatalk HD

[Robny]

Thanks,

So am I understanding correctly that I don't really need to use guide scope rings, I can use the regular tube rings that came with the scope?

As far as the camera is concerned, I've not really decided - I'm playing with the idea of using a standalone so I can be laptop free as I will be using a Canon D50

[Andymac79]

Yes. Save your cash and just use the standard rings and bolt the whole thing ontop.

I Know nothing of stand alones but for a camera, PHD guiding is free and brilliant

[Robny]

Yes. Save your cash and just use the standard rings and bolt the whole thing ontop.

My wife will be very happy to hear that

Think I'm going to ask a daft question now Here goes

If I don't need to use guide scope rings, then I presume the guide star does not have to be centred in the frame for it to guide? So long as it is bright enough anywhere in the frame?

Thanks Again

[Psychobilly]

Some of the standalone guiders liek the Synguider need you to pretty well "centre" the guide star on the chip - Skywatcher make a small adjustable guidescope mount for the purpose ...

http://www.firstlightoptics.com/guide-cameras/skywatcher-guidescope-mount.html

a "normal" guide cam and PHDguide can use a guide star anywhere in the FOV ...

Peter...

[Gina]

I use the ST80 and the scope rings it came with, a QHY5 camera and PHD. I have used the ST80 on top of my ED80 and beside it without a problem. PHD doesn't care where the guide star is within the frame and so far I have always found two or three stars or more withing the frame

[Robny]

Thanks Gina and all, I think this is the way I Will go

Thanks for the advice

[sgazer]

I used a ST-80 as a guide scope for a 150pds on a HEQ5. I settled for side by side using a wide dovetai like this http://www.firstligh...h-wide-top.html

I found it easier to lift and handle than on top, also I thought with them stacked up there would be more rotational force (due to the ST-80 being further out from the rotational point), but I guess there's very little in it and just down to personal preference.

With the ST-80, as the focuser is sloppy and has to be wound out quite far, plus an extension is needed, the guide cam could more around quite a bit, so I had to add a couple of extension arms to brace the cam. This set up worked very well though.

I tried adjustable rings for the ST-80, but they were way too much hassle and didn't allow me to brace the camera. The guide cam I was using (a Mintron) always found a guide star anyhow.

[jezhughes]

Some of the standalone guiders liek the Synguider need you to pretty well "centre" the guide star on the chip - Skywatcher make a small adjustable guidescope mount for the purpose ...

http://www.firstligh...cope-mount.html

a "normal" guide cam and PHDguide can use a guide star anywhere in the FOV ...

Peter...

From experience i wouldn't recommend these. I had a ridiculous amount of flex in mine regardless of how much i tuned and tightened the whole thing up. I also rarely found i needed to adjust it, so went back to using an ADM mount. now an OAG.

Just personal preference. there's better things to spend £100+ on

[Psychobilly]

From experience i wouldn't recommend these. I had a ridiculous amount of flex in mine regardless of how much i tuned and tightened the whole thing up. I also rarely found i needed to adjust it, so went back to using an ADM mount. now an OAG.

Just personal preference. there's better things to spend £100+ on

Thats a bit disappointing really.... I only used the Synguider when I was shooting at realtively short FL's with camera lenses so could live with slewing the mount to centre the guidestar as it didnt massively alter the FOV...

Peter...

[Robny]

I'm kind of edging now towards using a scope rings that came with the ST80 with a QHY and an acquired netbook

[Andymac79]

Sound idea. You dont need much power to run PHD, I use a Toshiba T30 (for the serial port) with 520 ram and its fine

[Uranium235]

With my old ST80 I also used to use one of those cheap 0.5x 1.25" reducers screwed on to the QHY5 nosepiece. It brightens things up and increases the FOV, the stars arent perfect towards the edge - bit they're good enough to guide off.

Top tip #1 for when using guidescope rings:

Get an old leather belt and cut it into lengths that will fit & overlap around the circumference of your OTA, and where the guidescope ring bolts are likely to touch. Get some adhesive hook and eye tape (velcro) then pop that on the belt, make sure that the grippy side of the leather belt (usually the underside) is face down. Then you can tighten up fully without worring about wrecking the paintwork or denting the scope.

I have an ED80 in guidescope rings, and its done an 8 hours in 10 min subs with no dodgy stars... apart from the ones with cloud damage.... grrr!

[Tinker1947]

Mine fits like this, nice sturdy no wobble fit.....

[Mike_F]

With the ST-80, as the focuser is sloppy and has to be wound out quite far, plus an extension is needed, the guide cam could more around quite a bit, so I had to add a couple of extension arms to brace the cam. This set up worked very well though.

+1 for this. I had focuser slop problems with my Equinox 80 APO when I tried to use that as a guide scope. Even at that point in Skywatcher's range of refractor scopes, if you have the focuser racked out a fair bit to achieve focus - there's far too much play.

All the expensive ADM dovetails and scope rings are pointless if the guide cam is waggling in the wind in a droopy focuser .

Currently waiting for a clear night to set up the shiny new Atik OAG in the imaging train as a result.

[Robny]

+1 for this. I had focuser slop problems with my Equinox 80 APO when I tried to use that as a guide scope. Even at that point in Skywatcher's range of refractor scopes, if you have the focuser racked out a fair bit to achieve focus - there's far too much play.

All the expensive ADM dovetails and scope rings are pointless if the guide cam is waggling in the wind in a droopy focuser .

Currently waiting for a clear night to set up the shiny new Atik OAG in the imaging train as a result.

Thanks for the additional info

So I will most likely need an extension tube to obtain focus? And think of some way to support the camera?

Anything else to consider

Thanks again

[Mike_F]

Thanks for the additional info

So I will most likely need an extension tube to obtain focus? And think of some way to support the camera?

Anything else to consider

Thanks again

I was using a 2" extension tube - but even then I had to rack the focuser out quite a way because the scope was originally designed to be used with a diagonal - which adds a chunk to the optical path length in normal use. A longer extension will of course exert more leverage on the focuser and exacerbate any slop - which is why I decided to cut my losses and switch to OAG. (Well, that and I'm guiding an SCT - which with mirror flop as well has enough differential flexure issues on its own, never mind having a floppy guide scope as well.)

For your Quattro - mirror flop shouldn't be an issue - so an ST80 should work well as long as you can get the whole rig sufficiently rigid.

[Robny]

I was using a 2" extension tube - but even then I had to rack the focuser out quite a way because the scope was originally designed to be used with a diagonal - which adds a chunk to the optical path length in normal use. A longer extension will of course exert more leverage on the focuser and exacerbate any slop - which is why I decided to cut my losses and switch to OAG. (Well, that and I'm guiding an SCT - which with mirror flop as well has enough differential flexure issues on its own, never mind having a floppy guide scope as well.)

For your Quattro - mirror flop shouldn't be an issue - so an ST80 should work well as long as you can get the whole rig sufficiently rigid.

Thank you, I guess its a case if suck it and see

[ollypenrice]

I use a Baader dovetail clamp (Altair Astro also make them) which I bolt on top of the imaging scope. Then I have a dovetail on the guidescope in its standard rings. This way I can quick-release the guide scope for other purposes and also drop the solar scope on instead. Here you see the system with the solarscope in place. There is a second advantage in that you can fine tune the Dec balance by sliding the guide scope fore and aft. Dec balance is often very critial.

Olly

[Gina]

I find it surprising that several people are having problems with a floppy camera on their ST80s. I have no problem with my ST80 and QHY5 with camera stability. I use a suitable 2" extension tube (60mm I think) so that the focuser is not too far out. It's rock solid. I do have the focus locked. of course. But I set focus up when I got it (just off perfect focus) locked it and never looked back. I think the important point is to get a sufficiently long extension tube and have everything screwed up tight.

[ollypenrice]

Also check the three screws that pass through the rear of the blue main tube into the body of the focuser back end. These can be loose. As Gina says, there is no need for flexure. I Araldited a couple of Barlow bodies together for my setup. No flexure there...

Olly

[opticalpath]

A few years ago, there was an interesting article by Chris Peterson in Astrophoto Insight online magazine. Frustrated by guider mounting issues and flexure problems, he constructed a completely fixed guide scope by rigidly mounting an achromat objective lens on one end of a heavy dovetail bar, and a fixed camera on the other end. No tube, no focuser, no moving parts .... no flexure. IIRC, it was a 40mm diameter lens and only 200mm focal length, but he used it successfully to guide a LX200 imaging scope. An interesting approach.

Adrian