Giro Type Mounts - AZ Stiction

[AdeKing]

I've been using giro type mounts for a while and generally enjoy using them, but there is something which I've been unable to get rid of and is beginning to irritate me and that is Stiction on the AZ axis.

Balance on the Alt axis is not a problem and is is buttery smooth to move around with very little effort required.

However, whilst the AZ axis is lovely and smooth once it's moving, it requires significantly  more effort to move around the AZ axis and it's the initial effort which is a nuisance and causes me to overshoot the target needing me to backtrack.

I find it impossible to track smoothly at high magnification.

I've found this to be an issue with all three of my manual alt az mounts which comprise a Giro GR2, an Ercole Mini and now a full size Ercole.

I'm using a counterweight approx equal to the OTA, diagonal and eyepiece weight on the opposite side, even though the Ercole claims to not need a counterweight if the setup is use is under 8kg.

Things do improve with the weight added to the opposite side but it still needs significantly more effort to move that it does in Alt.

Distance to center of Counterweight to the AZ axis centre is the same as the distance from the centre of the axis to the centre of the OTA.

Mount is set up level.

So what am I missing, I know there are a lot of Giro type mount users out there on SGL, so do you have any suggestions of things that I've missed or is my expectation just too high and it's a case of that's how it is so deal with it.

Many thanks,

Ade

[Alan White]

Ah the joys of nudge,nudge, curse observing....

I don’t think you find yourself in a unique place Ade, the AZ always has some stiction present, I think it’s the nature of the beast, unless it’s on very nice bearings, and then things improve.

My Sabre has a bearing set not bush on AZ and it’s smoother than my Giro Ercole was, just.

I think the difference in tension between stiction and smoother movement is minute, and once found a magic place to be, then how my life goes, the knob gets knocked and the magic setting is gone again.

More trial and more error I think for you Ade.

[markse68]

57 minutes ago, AdeKing said:

Distance to center of Counterweight to the AZ axis centre is the same as the distance from the centre of the axis to the centre of the OTA.

Is the counterbalance weight the exact same weight as the ota? If not then it shouldn’t be the same distance to get perfect balance. you may find you’re pinching one side of the az bearing surface which might improve with more even weight distribution through better balancing?

edit: sorry you did say it was equal so ignore this

Edited August 8, 2020 by markse68

[iPeace]

9 minutes ago, AdeKing said:

is my expectation just too high

Having used (and very much enjoyed) the Ercole, Ercole Mini and Castor II, I'm inclined to state that there is a limit to how good it gets. Whether that's good enough is a question which I suspect comes down to personal habit and preference. If you too often find yourself having to 'suck it up and think of Galileo', then something is not right - for you.

33 minutes ago, AdeKing said:

do you have any suggestions

Well, you could consider using a lever (basically a longish pole attached to the side opposite the scope, used as a handle to pan around with). Perhaps you could fashion something to test the concept to see whether it does it for you before investing.

43 minutes ago, AdeKing said:

I find it impossible to track smoothly at high magnification.

The 'elephant in the room' is wearing a t-shirt with the message: "YOU NEED SLO MO".

I dislike how the above reads, as if I'm on some crusade of justification. I don't mean to be, I'd like to do without slo-mo myself and applaud those who do so (manually track a dob at high power, etc.). I've even fully enjoyed it to great extent, but my symptoms, which I recognise as yours, were only fully cured by using a slo-mo mount.

[John]

My Giro Ercole has a bit of this. I've owned three now and they have all had it to some extent. I have come to the conclusion that this is a characteristic of the design. I use counterweights to minimise it. Now that I know that it's there I can deal with it and tracking is OK. I have asked on other forums but not had any good suggestions about a cure.

I was thinking about getting in touch with Tele Optik and asking their advice

  http://www.donelasci.de/teleskop-tecnica.html

Having read a number of really positive reports on these mounts, with no mention of it, I was a little surprised to come across this issue with more than one example. I can't recall my Giro II having it but that was a long time ago so maybe it did

 

 

[Dave1]

1 hour ago, AdeKing said:

I've been using giro type mounts for a while and generally enjoy using them, but there is something which I've been unable to get rid of and is beginning to irritate me and that is Stiction on the AZ axis.

Balance on the Alt axis is not a problem and is is buttery smooth to move around with very little effort required.

However, whilst the AZ axis is lovely and smooth once it's moving, it requires significantly  more effort to move around the AZ axis and it's the initial effort which is a nuisance and causes me to overshoot the target needing me to backtrack.

I find it impossible to track smoothly at high magnification.

I've found this to be an issue with all three of my manual alt az mounts which comprise a Giro GR2, an Ercole Mini and now a full size Ercole.

I'm using a counterweight approx equal to the OTA, diagonal and eyepiece weight on the opposite side, even though the Ercole claims to not need a counterweight if the setup is use is under 8kg.

Things do improve with the weight added to the opposite side but it still needs significantly more effort to move that it does in Alt.

Distance to center of Counterweight to the AZ axis centre is the same as the distance from the centre of the axis to the centre of the OTA.

Mount is set up level.

So what am I missing, I know there are a lot of Giro type mount users out there on SGL, so do you have any suggestions of things that I've missed or is my expectation just too high and it's a case of that's how it is so deal with it.

Many thanks,

Ade

What AZ mount do you have? (edit, just read the bit where you state which three AZ mounts you have, ignore the question )

My Altair Sabre 2 as delivered to me had bad stiction on the AZ axis. The solution was to take it apart, clean what very little grease there was off  And I regreased liberally with Halfords Bikehut Teflon Grease. Never had a problem again.

These mounts really are quite simple, don't be afraid to get stuck in, if you are competent with tools.

Dave

Edited August 8, 2020 by Dave1

[John]

I ought to add that my Altair Sabre II had this as well so they are not immune from it.

I ought not to like using my Skytee II more than the wonderfully designed and made Ercole but I have to concede that it (the ST2) is my preferred mount and handles long, heavy scopes a little better as well

 

[AdeKing]

4 hours ago, Alan White said:

Ah the joys of nudge,nudge, curse observing....

I don’t think you find yourself in a unique place Ade, the AZ always has some stiction present, I think it’s the nature of the beast, unless it’s on very nice bearings, and then things improve.

My Sabre has a bearing set not bush on AZ and it’s smoother than my Giro Ercole was, just.

I think the difference in tension between stiction and smoother movement is minute, and once found a magic place to be, then how my life goes, the knob gets knocked and the magic setting is gone again.

More trial and more error I think for you Ade.

Thanks Alan, I've been using it with zero tension on AZ tension screw so it must be background Stiction as it were.

I'm still trying to convince myself that I don't need the expense of the AZ100 and when I picked up the Ercole for a good price recently I thought I'd struck gold, but clearly more learning required. I've obviously been spoilt with goto and tracking mounts recently.

I remember a similar problem with the Skywatcher Dob but I solved that with a lazy Susan bearing mod, rather too effectively in the end so needed to add some friction back in at the end.

3 hours ago, markse68 said:

Is the counterbalance weight the exact same weight as the ota? If not then it shouldn’t be the same distance to get perfect balance. you may find you’re pinching one side of the az bearing surface which might improve with more even weight distribution through better balancing?

edit: sorry you did say it was equal so ignore this

The counterweight is not precisely the same weight, but within 100g of the OTA and accessories so not significantly different.  I'm going to try again tonight and just keep fiddling with the location of the counterweight to see if I can improve.

3 hours ago, iPeace said:

Having used (and very much enjoyed) the Ercole, Ercole Mini and Castor II, I'm inclined to state that there is a limit to how good it gets. Whether that's good enough is a question which I suspect comes down to personal habit and preference. If you too often find yourself having to 'suck it up and think of Galileo', then something is not right - for you.

Well, you could consider using a lever (basically a longish pole attached to the side opposite the scope, used as a handle to pan around with). Perhaps you could fashion something to test the concept to see whether it does it for you before investing.

The 'elephant in the room' is wearing a t-shirt with the message: "YOU NEED SLO MO".

I dislike how the above reads, as if I'm on some crusade of justification. I don't mean to be, I'd like to do without slo-mo myself and applaud those who do so (manually track a dob at high power, etc.). I've even fully enjoyed it to great extent, but my symptoms, which I recognise as yours, were only fully cured by using a slo-mo mount.

Thanks Mike, I've seen so much praise lauded on these mounts and absolutely no mention of Stiction on the AZ axis that maybe I was expecting too much.

Regarding slow-mo, this is very much an effort to convince myself that I don't need an AZ8 or an AZ100 so I'll see how I go.

I am looking at whether I can adapt the lever from my Gitzo birding mount. I thought that I had once seen a guiding handle for an Ercole but I'm darned if I can find it now.

3 hours ago, John said:

My Giro Ercole has a bit of this. I've owned three now and they have all had it to some extent. I have come to the conclusion that this is a characteristic of the design. I use counterweights to minimise it. Now that I know that it's there I can deal with it and tracking is OK. I have asked on other forums but not had any good suggestions about a cure.

I was thinking about getting in touch with Tele Optik and asking their advice

  http://www.donelasci.de/teleskop-tecnica.html

Having read a number of really positive reports on these mounts, with no mention of it, I was a little surprised to come across this issue with more than one example. I can't recall my Giro II having it but that was a long time ago so maybe it did

Thanks John, maybe it is a case that I'm being over picky and it is in fact inherent in the design and a fact of life that I need to adapt to.

Like you I don't ever recall seeing mention if it in any of the reviews that I read of these mounts.

I am using with short tube Fracs with them at the moment (ST102/ZS66) maybe it is less noticeable with a longer tube. I tend to move about the AZ axis by grabbing the diagonal whether that be right or wrong, so maybe the longer length of the ED100 might reduce the issue.

3 hours ago, Dave1 said:

What AZ mount do you have? (edit, just read the bit where you state which three AZ mounts you have, ignore the question )

My Altair Sabre 2 as delivered to me had bad stiction on the AZ axis. The solution was to take it apart, clean what very little grease there was off  And I regreased liberally with Halfords Bikehut Teflon Grease. Never had a problem again.

These mounts really are quite simple, don't be afraid to get stuck in, if you are competent with tools.

Dave

Thanks Dave, I do need to strip down the GR2 version as the tension adjustment screws don't seem to work very well so I'll take a look.

3 hours ago, John said:

I ought to add that my Altair Sabre II had this as well so they are not immune from it.

I ought not to like using my Skytee II more than the wonderfully designed and made Ercole but I have to concede that it (the ST2) is my preferred mount and handles long, heavy scopes a little better as well

Thanks John, I did have a Skytee ii at one point and do kind of regret moving it on, but such is life.

Edited August 8, 2020 by AdeKing
Spelling

[Alan White]

Ade, it could well be the lightness of the scopes used, sometimes more mass makes things run more smoothly.

[AdeKing]

Thanks Alan, I did wonder whether this might have an impact, I'll try it with the ED100 or ED120 and see what difference it makes.

I knew it would be a re-learning curve as I haven't used a manual Alt-Az for a while.

More tinkering and playing, then tinkering and playing is in order I feel.

[John]

35 minutes ago, Alan White said:

Ade, it could well be the lightness of the scopes used, sometimes more mass makes things run more smoothly.

That's a good point Alan. I remember having both my ED120 and an ED150 on the mount when I was testing the latter and the mount seemed very smooth on both axis then.

Maybe these things do better when heavily loaded ?

Not that I'm going to lash out on an ED150 just to act as a counterweight to the ED120 though !

 

[iPeace]

I now recall that one of these mounts I used worked as close to perfection as one could hope for - but only when two particular scopes were deployed in a particular configuration. It was a real 'wow' moment for me. The only useful explanation must concern weight and balance. In your situation, I suppose I would be trying to determine whether this 'perfect point' exists, with the scope on one side and the empty counterweight bar on the other, gradually applying downward force by hand until the mount (almost) starts moving by itself; if that point exists, then it's a matter of re-creating it with counterweights, adjusting one millimetre at a time.

I'm sure the above reflects at least in spirit your efforts so far.

[Mark at Beaufort]

@AdeI had the original SkyTee mount and I did become frustrated that the Az side did not always move slowly. In the end I used a handle on the one side to make things easier. I attach the only photo I can find to show the handle in situ.

In the end I bought the SkyTee 2 which I felt was much better because of the slow motion controls.

[Solar B]

That set up looks superb Mark with a wonderful solution 

Ade I personally could not do without slo mo controls as I require them to glide over 

the solar disk ... and I guess that's the main reason I like my ST2 , it's far from perfect 

but performs well enough and I like the ability to mount a longer FL refractor on top 

but tend to use the sides for normal solar obs.

PS I do like the look of your new Giro though 👍

Brian 

[John]

I'll say it again, there is still a niche for a good capacity alt-azimuth mount, with slow motion controls, that is priced somewhere between the Skytee II / Ercole and the £1K plus units like the AZ100.

I'm glad that I hung onto my Skytee II. Far from perfect but it does what it does competently and has a good capacity for it's price once the saddles are replaced and it's on a stronger tripod.

 

 

 

[markse68]

4 hours ago, iPeace said:

I now recall that one of these mounts I used worked as close to perfection as one could hope for - but only when two particular scopes were deployed in a particular configuration. It was a real 'wow' moment for me. The only useful explanation must concern weight and balance. In your situation, I suppose I would be trying to determine whether this 'perfect point' exists, with the scope on one side and the empty counterweight bar on the other, gradually applying downward force by hand until the mount (almost) starts moving by itself; if that point exists, then it's a matter of re-creating it with counterweights, adjusting one millimetre at a time.

I'm sure the above reflects at least in spirit your efforts so far.

Does the Gyro use PTFE thrust bearing for the AZ? Interestingly ptfe coefficient of friction reduces with load up to a point. So if it does, a couple of thoughts- you could try a heavier counterbalance weight closer to the pivot point to try to reduce that cof. Or maybe a lighter weight further from the pivot to increase the rotational inertia (it increases by square of distance from pivot) which might help smooth out the motion and make the stiction less noticeable? Worth an experiment perhaps.

 

[iPeace]

50 minutes ago, markse68 said:

Does the Gyro use PTFE thrust bearing for the AZ?

I don't know - was never much inclined to disassemble...

52 minutes ago, markse68 said:

Interestingly ptfe coefficient of friction reduces with load up to a point. So if it does, a couple of thoughts- you could try a heavier counterbalance weight closer to the pivot point to try to reduce that cof. Or maybe a lighter weight further from the pivot to increase the rotational inertia (it increases by square of distance from pivot) which might help smooth out the motion and make the stiction less noticeable? Worth an experiment perhaps.

That's very interesting stuff, thanks.

[John]

The Ercole specs say lubricant-free bearings.

"The GIRO-Ercole mount differs through the new radial/axial bearing without lubrication. Inside their are high quality plain bearings which counteracts the rotation and a lateral load. Furthermore the support points and length of bearing has been extended significantly. So the mount can carry more weight."

 

[Stu]

Like John, I have always found these mounts work best with two scopes on them. Somehow the imbalances seem to cancel each other out, and perhaps the additional moment of inertia helps to damp the motions down a little. There’s nothing I enjoy more than say an Ha and white light scope side by side, or widefield and higher power scopes at night.

The AZ100 is better, obviously because of its overall size and rigidity but same as for the SkyTee2, the slow motion controls really help.

Even the Scopetech Zero Mount is better in this respect because it has the slo mos and the bearing clutches.

[AdeKing]

18 hours ago, Alan White said:

Ade, it could well be the lightness of the scopes used, sometimes more mass makes things run more smoothly.

Thanks Alan, I tried with the 102 f/11 today so a completely different beast, quite a bit heavier and almost 4x the length, but similar symptoms.

It is definitely improved by adding a counterweight and by gradually moving the weight along the counterweight shaft I found a sweet point where the Stiction was much reduced though not eliminated but much more tolerable.

17 hours ago, John said:

That's a good point Alan. I remember having both my ED120 and an ED150 on the mount when I was testing the latter and the mount seemed very smooth on both axis then.

 

8 hours ago, iPeace said:

I now recall that one of these mounts I used worked as close to perfection as one could hope for - but only when two particular scopes were deployed in a particular configuration. It was a real 'wow' moment for me. The only useful explanation must concern weight and balance. In your situation, I suppose I would be trying to determine whether this 'perfect point' exists, with the scope on one side and the empty counterweight bar on the other, gradually applying downward force by hand until the mount (almost) starts moving by itself; if that point exists, then it's a matter of re-creating it with counterweights, adjusting one millimetre at a time.

I'm sure the above reflects at least in spirit your efforts so far.

John and Mike, I think this is something I need to investigate further. Watch this space.

5 hours ago, Solar B said:

That set up looks superb Mark with a wonderful solution 

Ade I personally could not do without slo mo controls as I require them to glide over 

the solar disk ... and I guess that's the main reason I like my ST2 , it's far from perfect 

but performs well enough and I like the ability to mount a longer FL refractor on top 

but tend to use the sides for normal solar obs.

PS I do like the look of your new Giro though 👍

Brian 

Brian, I do love the slow-mo controls. I had a ST2 off you ages ago though it was under utilised so got moved on to fund something else, something I'm now regretting.

4 hours ago, John said:

I'll say it again, there is still a niche for a good capacity alt-azimuth mount, with slow motion controls, that is priced somewhere between the Skytee II / Ercole and the £1K plus units like the AZ100.

I'm glad that I hung onto my Skytee II. Far from perfect but it does what it does competently and has a good capacity for it's price once the saddles are replaced and it's on a stronger tripod.

I hear you John, there is still a gap in the market for a mount with slow-mo controls at that price point. 

3 hours ago, markse68 said:

Does the Gyro use PTFE thrust bearing for the AZ? Interestingly ptfe coefficient of friction reduces with load up to a point. So if it does, a couple of thoughts- you could try a heavier counterbalance weight closer to the pivot point to try to reduce that cof. Or maybe a lighter weight further from the pivot to increase the rotational inertia (it increases by square of distance from pivot) which might help smooth out the motion and make the stiction less noticeable? Worth an experiment perhaps.

I'm not sure, I found this earlier which suggests polymer bearings, but I couldn't see a date when the page was last updated browsing on my phone.

http://www.donelasci.de/mounts.html

Spec sheets on other sites suggest normal bearings.

2 hours ago, Stu said:

Like John, I have always found these mounts work best with two scopes on them. Somehow the imbalances seem to cancel each other out, and perhaps the additional moment of inertia helps to damp the motions down a little. There’s nothing I enjoy more than say an Ha and white light scope side by side, or widefield and higher power scopes at night.

The AZ100 is better, obviously because of its overall size and rigidity but same as for the SkyTee2, the slow motion controls really help.

Even the Scopetech Zero Mount is better in this respect because it has the slo mos and the bearing clutches.

Stu, thanks for popping in. I saw your post and have just spent a pleasant half hour observing with the LS60DS on one side and the ZS66 and Cool Ceramic wedge on the other and it's like a different mount.

There is still a bit of initial Stiction that needs to be overcome but nowhere near as much as with a solo scope.

I know neither of the attached scopes need such a heavy duty mount but everyone says that it's better to be over mounted 🤣.

A bit more effort to set up but it's been a real eye opener and much more pleasant to use.

I clearly need to do this more often goodness knows, it's not like I haven't got enough Fracs to choose from.

I don't understand the reasons for it. It's kind of like suspending a weight from a tripod for added stability. Doesn't look like it'll work, but it just does.

Thanks all, I'll have more of a play and report back.

[AdeKing]

6 hours ago, Mark at Beaufort said:

@AdeI had the original SkyTee mount and I did become frustrated that the Az side did not always move slowly. In the end I used a handle on the one side to make things easier. I attach the only photo I can find to show the handle in situ.

In the end I bought the SkyTee 2 which I felt was much better because of the slow motion controls.

Thanks Mark, this is the type of thing I'm sure I've seen commercially available, but looking at that I could drill and tap a hole into one of my dovetails and use the handle from a cheap old Slik Prototype tripod I picked up recently.

At one point I had two SkyTee 2 mounts but moved them on as I found the controls awkward to use when I had Newts. Now I'm using Fracs it's looking like an attractive option once again.

Ummmm, here we go again.

[AdeKing]

Deleted: Duplicate Post

Edited August 10, 2020 by AdeKing
Deleted: Duplicate Post

[AdeKing]

Oh blast, this thread seems to be reinforcing what I've probably known all along that I need slow-mo controls.

It's not doing a very good job of convincing me that I don't need one of those fancy bells and whistles AZ100 mounts, which is what I hoped the Ercole would do.

In the meantime here is the solar setup I've been having fun with this afternoon.

 

[John]

Slow motions are very useful I agree. I can cope OK without if the mount motion is smooth on both axis.

I'm delighted with my T-Rex which suits my 130mm F/9.2 perfectly. The Ercole and the Skytee II carried it OK but the T-Rex showed me what a top end alt-az mount can do. Unfortunately the T-Rex is out of production and getting on for AZ100 in terms of pricing if you can find one:

 

[Macavity]

When I had a nice (Red!) Giro III mount, I used to measure the distance from
the center of the scope (and centre of that the counterweight) from the axis.

The distances are not always equal in Giro mounts. It is not as easy to judge
balance across the Azimuth axis (as it is in Altitude). So I would WEIGH the
scope (including the rings, disgoneal, finder, eyepiece etc.) and then do a
(back of envelope!) "See Saw calculation" (Weight x distance etc.) and then
CALCULATE the *required* counterweight to balance the system exactly.

A bit excessive? lol. But it worked for me. (Sorry if this has been noted!!!)
I could even play "silly beggars" and SPIN the axes around and around! 🥳
But then such *precise* balance can become an issue in it's own right...

I do find that my SkyTee II has a slight wobble on the Azimuth axis. So I
tend to use a slight *imbalace* so that it does not suddenly "slop" over!
As is the case with these mounts it is a tad non-obvious how one might
even tighten up the Azimuth axis. 🙄

Edited August 9, 2020 by Macavity