I'm pickin' up bad vibrations

[Basementboy]

Hi, I have a problem I'm hoping someone might be able to help me with.

I am experiencing quite noticeable vibrations – a good 3+ seconds to settle fully after a minor tap or any movement of the telescope – on my setup.

I have a TS Optics 115 Photoline apo triplet (OTA 6.5kg) and a 6" OOUK Newtonian (OTA 4.5kg).

They're mounted on a Sky-Watcher AZ5, bought secondhand in seemingly very good condition, and a SW 3/8 steel tripod, bought new from FLO. 

The AZ5 reportedly takes a 5kg payload, but I have read that it should easily take 9kg with a good tripod – which is why I bought the steel tripod.

I have tried tightening the screws everywhere, and I think I've got the tube rings squeezed on pretty tight. They're also reasonably centered, on both OTAs, and I've tried mounting the OTAs in slightly different positions – doesn't seem to make much difference.

I'm not using any crazy accessories or grenade-like eyepieces – the biggest I have is a Baader Hyperion, but regardless I am experiencing the problem without any EPs inserted.

The tubes just seem to kind of "twang".

It's worst on the Newt. But even the refractor vibrates more than it did on my first mount, an AZ3, which I had written off as "bad" but now seems to have at least performed its primary function well enough. 

I thought perhaps it was the nature of a dovetail mount that a tiny screw, digging sideways into a metal plate, would be a "weak point" in terms of vibrations – but @Tiny Clanger points out that it's not really the screw that takes the force, but the plate opposite, which spreads it out.

So I'm stumped.

Any advice gratefully received 🙏

Edited July 13, 2021 by Basementboy

[John]

What focal ratio is your 6 inch newtonian ?

The length of the scope tube can put the mount under pressure / strain even if the actual weight is well within the stated capacity I've found

I suspect the single arm AZ5 is just not up to the job of holding the scopes steady at higher magnifications ?

I tried putting my old AZ4 (which I think is a little stronger than the AZ5) on a 2 inch steel tubed tripod (EQ6 type) but it was still not up to the task of holding my ED120 F/7.5 refractor steady at anything above medium magnifications.

You probably need something like a Skytee II or a Giro / Sabre mount to hold these scopes really steadily.

 

[Highburymark]

9kg sounds like a huge load for the AZ5 - even with a strong tripod. Unfortunately think you’ll need a beefier mount.

[KP82]

Agreed with what have bee said above. I had an AZ5 3 years ago and a 4" f/7 was the max I'd put on it even with the SW 1.75" steel tripod.

Edited July 13, 2021 by KP82

[Highburymark]

3 minutes ago, John said:

 

I tried putting my old AZ4 (which I think is a little stronger than the AZ5) on a 2 inch steel tubed tripod (EQ6 type) but it was still not up to the task of holding my ED120 F/7.5 refractor steady at anything above medium magnifications.

You probably need something like a Skytee II or a Giro / Sabre mount to hold these scopes really steadily.

 

I agree John. The AZ5 also has that single screw clamp which can’t be swapped for an ADM clamp

[Basementboy]

3 minutes ago, John said:

What focal ratio is your 6 inch newtonian ?

 

It's F5 ... ie 750mm long. To be honest I didn't think that was particularly unwieldy, given that the Sky-Watcher Explorer 150 comes packaged with an EQ3. Or does the counterweight bar help in that case?

[Basementboy]

4 minutes ago, Highburymark said:

9kg sounds like a huge load for the AZ5 - even with a strong tripod. Unfortunately think you’ll need a beefier mount.

My setup is probably more like 7.5kg for the frac and maybe 6-ish for the Newt ... and I definitely did read several people say that the steel tripod should allow it to handle a few extra kilos. But maybe that was wrong ... or perhaps only applicable to shorter OTAs, eg a Mak

[Basementboy]

6 minutes ago, KP82 said:

Agreed with what John said. I had an AZ5 3 years ago and a 4" f/7 was the max I'd put on it even with the SW 1.75" steel tripod.

Damn, wish I'd spoken to you earlier. Although my frac is only 4.5" f/7 ... I remain somewhat surprised that the AZ5 can't handle it. But hey ho, you can't fool nature I suppose

[Basementboy]

6 minutes ago, Highburymark said:

I agree John. The AZ5 also has that single screw clamp which can’t be swapped for an ADM clamp

Is a single-screw clamp more prone to vibrations?

[johninderby]

I did have an AZ5 and after trying a number of scopes on it found that 5kg was about the practical limit and then that was for a short scope. Even using a Berlebach tripod didn’t help.

Think SW has removed any reference to the weight limli with the steel tripod or at least I couldn't find mention of it any more except on a few dealers websites but then many dealers websites contain outdated info.

Agree with John that a Skytee would be far better and would easily handle your scopes.

Edited July 13, 2021 by johninderby

[Highburymark]

19 minutes ago, Basementboy said:

Is a single-screw clamp more prone to vibrations?

Tbh I don’t know for sure - those single screw clamps work really well with modest scopes, but I’ve always presumed that spreading the load over a wider contact surface reduced vibrations. 

[Basementboy]

5 minutes ago, johninderby said:

Think SW has removed any reference to the weight limli with the steel tripod or at least I couldn't find mention of it any more except on a few dealers websites but then many dealers websites contain outdated info.

 

Dastardly! 

Yeah I had considered the Skytee ... it's just a weight issue for me, given I need to carry my gear to the roof for any decent views. But – we struggle on ...

Thanks John, appreciate it

[Basementboy]

4 minutes ago, Highburymark said:

Tbh I don’t know for sure - those single screw clamps work really well with modest scopes, but I’ve always presumed that spreading the load over a wider contact surface reduced vibrations. 

Makes sense to me too, yeah. Thanks anyway

[johninderby]

Perhaps the Giro Ercole Mini which will actually handle 9kg? 🤔

[ScouseSpaceCadet]

Really strange because my ST120 was quite beefy with a 50mm raci and it sat nicely on the AZ5. Likewise the 150i newtonian with upgraded focuser and tube rings. The current f7 4" refractor is fine too. The only real issue I've encountered is near or at zenith, the clutches need to be super tight for the slomo cables to work. Fully loaded the heaviest the mount has held is approx 6.5 kilos but I don't think more than that is practical.

Try tightening a touch the 3 screws holding the dovetail clamp.

 

6" Newt on the AZ5 observing Mars last Autumn.

 

Moon watching with an Altair Starwave 102ED f7.

Edited July 13, 2021 by ScouseSpaceCadet
3 screws

[Stu]

42 minutes ago, johninderby said:

Perhaps the Giro Ercole Mini which will actually handle 9kg? 🤔

That’s probably a good shout, quite light and would handle the weight, particularly if on a 2” Stainless Steel tripod. I used to have my Giro-WR loaded up fairly well and it coped well if on a decent tripod. They work better with a dual scope setup I think, balance is easier to reach.

Is the newt worse because of flexing in the tube, rather than in the clamp?

[ScouseSpaceCadet]

I meant to add, has the op moved the mount arm to the upright position by moving the two fixing bolts were it attaches to the base? This balances the load better. See my second pic.

Edited July 13, 2021 by ScouseSpaceCadet

[Stu]

3 minutes ago, ScouseSpaceCadet said:

I meant to add, has the op moved the mount arm to the upright position by moving the two fixing bolts were it attaches to the base? This balances the load better. See my second pic.

Does this stop you reaching the zenith? Not that that is a major problem because it is blooming awkward observing there anyway! 🤪🤪

[ScouseSpaceCadet]

4 minutes ago, Stu said:

Does this stop you reaching the zenith? Not that that is a major problem because it is blooming awkward observing there anyway! 🤪🤪

Iirc if the scope isn't too fat or long it should do or very nearly... In the second pic there's still a few cm travel remaining.

Edited July 13, 2021 by ScouseSpaceCadet

[Basementboy]

On 13/07/2021 at 19:22, Stu said:

Is the newt worse because of flexing in the tube, rather than in the clamp?

I suspect so – I play drums and the bigger ones vibrate longer

[Basementboy]

On 13/07/2021 at 19:28, ScouseSpaceCadet said:

I meant to add, has the op moved the mount arm to the upright position by moving the two fixing bolts were it attaches to the base? This balances the load better. See my second pic.

Aha!!!

Sorry for the delay, but I just got a chance now to try this .............. and it worked

Well, mostly. It has reduced the vibrations noticeably. Some remain but it's a big improvement for such a small adjustment.

I suspect it explains why the AZ3 was, somewhat surprisingly, shaking less – because the clamp is directly above the centre, so all the force goes straight down into the tripod.

Whereas the AZ5, when angled out, has to bear a lot the force in the arm. So when it's readjusted into a more vertical position then the tripod can take more of the vertical brunt of the weight.

A thousand thanks Top Team! Off tomorrow to Suffolk in the Ferrariat for some hopefully dark – and now less wobbly – skies!

 

[ScouseSpaceCadet]

11 hours ago, Basementboy said:

Aha!!!

Sorry for the delay, but I just got a chance now to try this .............. and it worked

Well, mostly. It has reduced the vibrations noticeably. Some remain but it's a big improvement for such a small adjustment.

I suspect it explains why the AZ3 was, somewhat surprisingly, shaking less – because the clamp is directly above the centre, so all the force goes straight down into the tripod.

Whereas the AZ5, when angled out, has to bear a lot the force in the arm. So when it's readjusted into a more vertical position then the tripod can take more of the vertical brunt of the weight.

A thousand thanks Top Team! Off tomorrow to Suffolk in the Ferrariat for some hopefully dark – and now less wobbly – skies!

 

Glad it's better. Good luck the forecasts are great. 😀