Big scope tiny mount

[Elp]

3 minutes ago, CraigT82 said:

I think the Berlebachs have some kind of hard stop to the leg spread to prevent that kind of incident? 

I'd have to look, they certainly don't open flat, but on the side of each leg is a tensioning lever, you can lock the legs in the desired angled position, at least on my Uni. You can also unscrew the rubber feet backward to reveal leg spikes to sink them into grass for more stability.

Edited August 10 by Elp

[CraigT82]

15 minutes ago, Elp said:

The ZWOs are designed to work in EQ and alt az, so within their scope weight limits they work fine. Fine slewing my am3 when I was doing visual solar induced no vibration whatsoever, and that's on a CF tripod.

Larger heavier scope, needs a larger mount and tripod, this has never changed.

What scope do you have on the AM3 and where does it sit within the stated payload capacity? 
 

The smaller mounts like the AM3 will generally carry the smaller scopes closer to the mount, and the centre line of the scope will probably sit well inside the tipping line (as described by Rusted) of the tripod. I think as you scale up with the bigger HD mounts carrying larger, heavier scopes, the distance between the centre of the mount and the centre of the scope will increase as well as the scope size, and unless the tripod footprint is also increasing in line with that you’re going to run the risk of the centre line of the scope being outside the tipping line - leading to topple?

[Elp]

I'm only using a SF102 refractor so small really but fully loaded for imaging it's nearly twice the weight of my hem15, the am3 is a bit more solid and has HD drives in both Ra and dec. I think with any setup you have to be mindful of what you're loading on top, where the heavy sections or imbalance points are, especially when the payload moves, not just in home postion. I'd certain err caution with a Newtonian simply because the increased box volume of the thing is shifting balance points away from the usually unloaded centre point of the rig, and as you say centerline of axis of mount, most manufacturers will advise what this distance should be within. But think of it like this, if the tripod/pier was sufficiently grounded, you wouldn't have an issue as long as the scope fits within the mounts capabilities.

It's wise to test the load moving around on a HD mount prior to using, especially if you intend for it to work automatically, one who does not is running into a potentially disastrous situation. I usually use my tripod with only one leg section extended, if I feel this is insufficient I'll extend another leg section to make it more stable. As you infer, consideration needs to be applied to the tripod or whatever the setup is mounted on top of, this is just common sense.

Edited August 10 by Elp

[cajen2]

2 hours ago, saac said:

My engineering pedantry anxiety is at Def Con  3 and climbing, stop conflating stiffness with toppling (tipping over) - the property of stiffness has nothing to do with the occurrence of toppling. Likewise, mass has nothing to do with load carrying capacity.  Now I know how Olly feels when folk can't tell the difference between a present participle and a gerund.  Arrrrrgh. 

Jim 

Not just Olly. Such things were my stock in trade for 40 years. I can forgive people, though, as most of them can do things I can't....

[Rusted]

Just for absolute clarity I offer the following:

The tripod manufacturers would have you believe you get the large bag of free sweeties with their ridiculously expensive products.
The truth is you only get the small bag of acid cough drops in the middle. 🥹

This is true, regardless of the Mass or Stiffness of the tripod construction at any price. Only increasing the spread will alter the true effective radius.
Increasing the mass of the tripod will only lower the centre of gravity relative to the load applied above the apex.
A triangular pyramid in solid concrete or lead will be extremely stiff and heavy but limited in its mobility and by its dimensions.
Increasing the height of the tripod will affect stability. Because it pushes the centre of gravity higher. [perhaps into the wind!]

Adding more legs to a tripod will increase the true tipping radius. Though it only approaches the foot radius with infinite numbers of feet.
A four legged stool is much safer than a 3-legged one when granddad has to reach that high shelf!
The problem with adding more legs is leveling and avoiding rocking between any two feet on uneven ground.
Designing the perfect tripod may well be beyond human intelligence. We've had thousands of years of failures.
Perhaps this is the first REAL design job for AI?

[Rusted]

How effective radius changes only slowly with increasing size of tripods.

[Rusted]

Here are two massive stands I used for my Fullerscopes Mk3 and a Vixen M90.
Both are far too heavy to lift for most ordinary people.
Both have an effective radius of 30cm.
Both can be moved with great difficulty by rolling around their base.
To the casual eye you'd think the massive tripod was much bigger and thus more stable.

Both can be tipped fairly easily by pulling sideways at the top. So both have similar stability.
I just measured the sideways pull required at the same height on the top tubes:
The tripod needed 8kg to lift the far foot. The disk stand needed 12kg! Q.E.D! 🤓

In my youth I once borrowed a 12" f/7 Newtonian from the local college.
It had a heavy, welded steel tripod which was difficult to lift. The footprint was rather small.
The mounting itself was a fairly short welded steel fork. The tube was a welded tubular skeleton.
The whole instrument was very heavy but so unstable as to be downright dangerous in use!
It would tip if you so much as glanced at it wrongly!
I learnt a valuable lesson in tripod stability from that brief experience!

 

Edited August 11 by Rusted
added data

[Rusted]

More boring stuff which might just save you thousands of pounds/dollars in broken equipment!
Or thousands of pounds in bitter disappointment after buying commercial products.
Remember that only the effective footprint radius affects overall stability with any 3-legged stand or tripod.
Though a really heavy "try-on" pier will probably reduce vibration from touching and the wind.
You can probably afford electric focusing and perhaps a dome as well. So that doesn't count. 😉

More real world proof of my thesis?
Here is my heavy, old Fullerscopes MkIV mounting carrying my hefty, 7" f/12 iStar DIY refractor.
I badly needed mobility to dodge all the trees and the house. So I added trailer pilot wheels.
This massive pier was welded from heavy section steel tube at work. I needed help to lift it into my trailer!!! It was impossibly heavy!
The thick wall rectangular legs have a span of 85cm from the centre of the 180mm/7" thick wall pier pipe out to the wheel's footprint.
Yet the whole thing was hideously unstable in rolling movement. I only just saved it from toppling several times!
To reduce rocking I swapped the pneumatic tires for solid rubber puncture free. This made it much worse!
The rolling resistance was much higher! So it wanted to tip on the slightest bump or slope on the lawn!
Massive weight + a larger, three legged foot spread, than any commercial tripod or pier = abject terror! 😆

The whole point of my series of posts is to educate you to make much better choices and hopefully fewer mistakes.
I have been experimenting with stands, tripods and piers for well over 60 years. I am still trying daft ideas.
What about a FOUR legged pier with firm, memory foam for feet? Or cylindrical compression dampers?
Fix your tripod or mobile pier to the ground somehow. A turnbuckle down to an eye-bolt anchor in the ground from the weight hook?

I'll be using concrete carport anchors and bracket for my new pier. No embarrassing slab or massive ground block.
Just lift the modestly sized anchors when you sell the house..  It worked for my fourteen feet high, pyramidal, plywood pier in my 2-story observatory.

 

[wimvb]

3 hours ago, Rusted said:

Adding more legs to a tripod will increase the true tipping radius.

Technically (semantically?) it will no longer be a tripod, of course. 😉

In my (very personal) opinion, loading a lightweight mount where you do away with counterweights because of weight considerations, with a bulky and heavy scope, and having to use a heavy tripod to keep the setup stable, just doesn’t make sense. The purpose of such a mount must be to get a lightweight setup; a lightweight mount on a lightweight (carbon fibre?) tripod with a lightweight telescope. Anything else seems to me just an exercise in shifting weights.

As for the original post/question, moving from an AZ-EQ6 to a harmonic drive mount makes sense if you have to set up and tear down every session. I had to do that until a few years ago, and it was the main reason why I built an observatory. Heavy mounts (including any counterweights) such as an AZ-EQ6, an EQ6-R, or larger, are better suited in a permanent setup. But if I’d have to move my setup again every session, I would get a mount, telescope, and tripod, that I could lift and carry around without having to remove anything. The alternative to a lightweight setup would be to make a heavier setup less mobile. A pier with a telescope cover, a roll away shed, or a micro observatory may be worth considering. A concrete pier can always be reused as a pedestal for a sundial, if you ever decide to give up on stargazing.

Edited August 11 by wimvb

[CraigT82]

1 hour ago, wimvb said:

Technically (semantically?) it will no longer be a tripod, of course. 😉

In my (very personal) opinion, loading a lightweight mount where you do away with counterweights because of weight considerations, with a bulky and heavy scope, and having to use a heavy tripod to keep the setup stable, just doesn’t make sense. The purpose of such a mount must be to get a lightweight setup; a lightweight mount on a lightweight (carbon fibre?) tripod with a lightweight telescope. Anything else seems to me just an exercise in shifting weights.

As for the original post/question, moving from an AZ-EQ6 to a harmonic drive mount makes sense if you have to set up and tear down every session. I had to do that until a few years ago, and it was the main reason why I built an observatory. Heavy mounts (including any counterweights) such as an AZ-EQ6, an EQ6-R, or larger, are better suited in a permanent setup. But if I’d have to move my setup again every session, I would get a mount, telescope, and tripod, that I could lift and carry around without having to remove anything. The alternative to a lightweight setup would be to make a heavier setup less mobile. A pier with a telescope cover, a roll away shed, or a micro observatory may be worth considering. A concrete pier can always be reused as a pedestal for a sundial, if you ever decide to give up on stargazing.

Exactly. I do set up and tear down each session, with all my kit stored in the garage and it’s a 40m move to get everything to the observing spot. Hence why I started looking at HD mounts due to their light weight and lack of counterweights. 

I first had doubts whether such a mount could hold my scope steady enough to not induce significant image wobble when observing, but now I realise that the real issue is the whole lot toppling over with a 25kg scope and no counterweights on board. 

I would need to accept counterweights - which defeats the point of the exercise- or come up with some sort of rolling pier design with a stable foootprint (not totally out of the question). Alternatively there is Rusted’s suggestion of some kind of tie down. Might be an idea if I put it on grass instead of the patio and use one of those dog lead ground screws with a chain or wire to a hook beneath the mount head 🤔

Edited August 11 by CraigT82

[Elp]

Honestly, if you're using a 25kg Newtonian you really shouldn't be mounting it on anything lighter, and should be on a dobsonian mount instead, especially if you're only doing visual. If you want lighter, look at the collapsible truss type dobsonians available.

[CraigT82]

3 hours ago, Elp said:

Honestly, if you're using a 25kg Newtonian you really shouldn't be mounting it on anything lighter, and should be on a dobsonian mount instead, especially if you're only doing visual. If you want lighter, look at the collapsible truss type dobsonians available.

No I do 50/50 visual and imaging. Mostly lunar planetary but have done a bit of short exposure deep sky with this scope, which didn’t work out but that wasn’t the mounts fault. 
 

I’m now thinking as long as the toppling issue could be tackled then a HD mount upgrade - without CW - is a possibility for me.  My scope is well within the range of something like this below with it’s stated payload of 31kg without CW.

https://www.firstlightoptics.com/harmonic-drive-mounts/ioptron-haz71-alt-az-strain-wave-mount.html

Quite an expense but what price can you put on avoiding a slipped disc! 

I have had one of the skywatcher tripod piers before and I liked it, so I’m now thinking one of them with 3 extra hinged steel or ally legs that fold out and with a levelling foot on each end, could be bolted to the column between the three existing legs, giving what should be a more stable hexagon shaped footprint. 

Edited August 11 by CraigT82

[Elp]

The lack of CWs is one of the reasons I changed, I can also pack the mounts in the same bags as my setups so single bag carry out solutions.

I think for your setup, it's better to get a pier tripod but again more carry out weight. There's a hefty ioptron for sale ATM on abs quite cheap, might be a bit tall though but looks like you'd have to severely overload it (IE mount a scope you can't lift without struggling or injuring yourself) in order to topple it over.

[CraigT82]

4 hours ago, wimvb said:

The alternative to a lightweight setup would be to make a heavier setup less mobile. A pier with a telescope cover, a roll away shed, or a micro observatory

Yeah this is the other option, however much much less likely to gain approval from the boss.

[wimvb]

6 hours ago, CraigT82 said:

Might be an idea if I put it on grass instead of the patio and use one of those dog lead ground screws with a chain or wire to a hook beneath the mount head 🤔

When the ground is wet, the tripod legs may settle unevenly, ruining the polar alignment. I solved this by driving fence post anchors into the ground, one for each tripod leg, similar to these. (I cut off the vertical parts.)

https://www.walmart.com/ip/Bob-s-Industrial-Supply-Concrete-Post-Anchor-4x4-Post-Base-Spike-Fence-Pergola-Deck-Bracket-4pk/958259314
 

The anchors actually made it easier to polar align.

[wimvb]

5 hours ago, CraigT82 said:

Quite an expense but what price can you put on avoiding a slipped disc! 

Ever considered a tripod dolly?

[CraigT82]

33 minutes ago, wimvb said:

When the ground is wet, the tripod legs may settle unevenly, ruining the polar alignment. I solved this by driving fence post anchors into the ground, one for each tripod leg, similar to these. (I cut off the vertical parts.)

https://www.walmart.com/ip/Bob-s-Industrial-Supply-Concrete-Post-Anchor-4x4-Post-Base-Spike-Fence-Pergola-Deck-Bracket-4pk/958259314
 

The anchors actually made it easier to polar align.

Yes I did something similar in the front garden at my old house. Used three topo survey station markers which are basically 400mm long steel nails with a small depression in the head. 

I have considered a scope trolley but the alleyway leading from my garage to the back garden is only 80cm wide. I do have a small circular furniture dolly which I stand the OTA on and I roll it down the alley to save me carrying it. Also the extra height of a scope trolley would put the EP way over my head and I’d need a step. 

Ideally I’d have this rig permanently set up in an obsy but that’s not going to happen. 

Suppose I could just build a wooden wheeled trolley that fits in the alley and pull the mount head, CW and tripod along in that, would be a lot cheaper than a brand new mount. 

[GTom]

On 10/08/2024 at 09:26, dweller25 said:

My interest peaked when I heard how much the harmonic drives could hold and how little they weighed, but I have seen a Youtube video that says without a counterweight there could be a risk of toppling over with heavier scopes.

So the counterweight and counterweight bar adds to the weight of the setup, loosing some of the advantage !

Simples: you put LOCALLY SOURCED rocks, 8L water bottles filled with wet sand, spare car wheel, diving leads, dead crocodile on the hook of your featherweight carbon tripod to keep the center of gravity in a proper place (aka avoid toppling over). Tripod weights don't need to be properly shaped/symmetrical/dense(!), etc as mount counterweights.
 

That's a huge advantage when you need to fly to the dark site. 

I am currently putting a maxed airline capable kit together, based on a quattro 150p. So far I was looking at cem26 and gem28 mounts, but that means I need to carry approx 10 kg proper counterweight, that adds a lot to the logistics.

[Elp]

37 minutes ago, GTom said:

gem28

The gem28 in its flight case with CWs probably weighs more than some of my whole imaging setups. Kind of puts it into perspective.

[GTom]

21 minutes ago, Elp said:

The gem28 in its flight case with CWs probably weighs more than some of my whole imaging setups. Kind of puts it into perspective.

The main difference is the CW. For a travel gear (=OTA is less than 10kg anyway) you simply don't bring one, neither the cw shaft. Astro carbon tripods are another great thing happened recently. My SW steel tripod is perfectly impossible to fly with. The Bexin ST402C was less than £200, weighs nothing compared to the steel one.

Also thinking on the Umi 17R, taxed-shipped cheaper than a second hand AM5. The SW revolution is definitely here!

Edited August 11 by GTom

[Elp]

1 hour ago, GTom said:

Bexin ST402C

Is that tripod tall enough at 80cm extended? I ask as I used to use my Leofoto which I bought for it's compactness as its around 60cm high extended, I can use my alt az mount visually with it with a light scope, somehow my eq mode azgti imaging rig also worked very well, but as soon as I removed the counterweight it wanted to fall over. So I couldn't use my HD mounts with it and bought longer tripods which I set around 1-1.5M high to get the tripod leg spread stability.

[GTom]

43 minutes ago, Elp said:

Is that tripod tall enough at 80cm extended? I ask as I used to use my Leofoto which I bought for it's compactness as its around 60cm high extended, I can use my alt az mount visually with it with a light scope, somehow my eq mode azgti imaging rig also worked very well, but as soon as I removed the counterweight it wanted to fall over. So I couldn't use my HD mounts with it and bought longer tripods which I set around 1-1.5M high to get the tripod leg spread stability.

Probably a pain for visual - not so much with a Newtonian. AP should be fine, especially if I consider wind protection.

Edited August 11 by GTom

[ollypenrice]

On 10/08/2024 at 21:50, saac said:

My engineering pedantry anxiety is at Def Con  3 and climbing, stop conflating stiffness with toppling (tipping over) - the property of stiffness has nothing to do with the occurrence of toppling. Likewise, mass has nothing to do with load carrying capacity.  Now I know how Olly feels when folk can't tell the difference between a present participle and a gerund.  Arrrrrgh. 

Jim 

Yes, we are talking about two things here.

The best portable anti-topple system is probably that used by Astro Physics. They make a portable pier with widely spread triple feet. (This is simply a special case of a tripod.) The clever bit, though, is that the pier is stiffened not by heavy tubular stays between feet and upper pier but simply by thin spokes in tension, one per foot. These are tightened as a last operation. A strut in compression needs its own resistance to deformation. If the strut is in tension, however, it does not.

Olly

[ollypenrice]

On 11/08/2024 at 09:37, wimvb said:

 The purpose of such a mount must be to get a lightweight setup; 

Not just lightweight. The small footprint and swept volume were critical to fitting this 'extra' rig into the observatory. There would be no room to swing counterweights.

We often hear from members whose other halves won't allow roll off roofs in the garden. This kind of rig is so small that a roll off ornamental feature would be enough to conceal it.

Olly

 

Edited August 12 by ollypenrice
typo

[Rusted]

My immediate response to weight carrying problems is to have one or more fixed piers.
Then you only need to carry the mounting and OTA. The pier takes care of toppling issues.

No piers allowed? Then use a lightweight tripod but have a screw eye where you want to use the mount.
Use a common fencing turnbuckle to tension a line or chain down from the tripod's weight hook.
No [anti-toppling] counterweights required.

You don't want anything sticking up in the grass to ruin the mower. Nor cause a tripping point on the patio.
Have something with a female screw thread sunken into the lawn with a rubber plug.
Or sink a pipe into the lawn with the threaded plug below mowing level. There are all kinds of screw plugs these days.
Similarly, put a screwed female socket in the patio to take your screw eye for tensioning your tripod against toppling.

You have just saved yourself carrying the counterweight and its bar.

I am a believer in wheelbarrows to avoid carrying. Throw a thick blanket or old sleeping bag in the barrow to protect your nice kit.
No old blanket or sleeping bag? Your nearest charity shop will help.