Big scope tiny mount

[Alan White]

28 minutes ago, ollypenrice said:

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.

 

Thread drift for which I apologise.

Interesting block @ollypenrice, what are they solid or hollow?
Of course they will be a French block and available in blighty no doubt.
 

[CraigT82]

2 hours ago, Rusted said:

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.

You know what I do actually have a wheelbarrow somewhere, was left here when we bought the house…. Knew it would come in handy one day! 

[saac]

The main engineering advantage of a strain wave drive is its high torque output in comparison to traditional geared drives of similar mass (typically by a factor of 3).  When applied to telescope mounts it's this high torque to mass ratio that allows designers to specify designs which  have significant weight savings over traditional geared GEM mounts.  The load capacity is derived directly from the strain wave drive's large holding torque and not its mass.  These drives can on first sight appear somewhat incongruous when carrying larger mounts. However, one only needs to look to the strain wave drive origin in robotics (manufacturing) to see how they excel in delivering high torque, high load carrying capacity and repeatability of movement.   Toppling in a mount is primarily a function of geometry. Hence, the strain wave mount, under certain configurations  is as susceptible as any conventional mount, to toppling. We really shouldn't be surprised by that but it would be incorrect to hold its relative mass advantage as the problem.  If a mount's load (geometric) configuration places it outside its operational parameters then a counterweight is needed.  

Jim  

Edited August 12 by saac

[saac]

2 hours ago, ollypenrice said:

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

 

I think you have hit on something here Olly with that observation.  I often find myself reflecting on the micro observatory built by @Skipper Billy considering it to be such an efficient and pleasing design.  The emergence of strain wave drives as a dominant mount design could well benefit these type of micro observatories. This could only be a positive consequence of the counterweight free feature making it an attractive solution where space is limited. 

Jim  

 

[CraigT82]

20 hours ago, GTom said:

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.

Interestingly there has been a couple of posts over on CN by visual guys using HD mounts who have resorted to hanging bags of rock from the tripod head to try to stablise the rig and prevent tip over.

[Rusted]

1 hour ago, saac said:

The main engineering advantage of a strain wave drive is its high torque output in comparison to traditional geared drives of similar mass (typically by a factor of 3).  When applied to telescope mounts it's this high torque to mass ratio that allows designers to specify designs which  have significant weight savings over traditional geared GEM mounts.  The load capacity is derived directly from the strain wave drive's large holding torque and not its mass.  These drives can on first sight appear somewhat incongruous when carrying larger mounts. However, one only needs to look to the strain wave drive origin in robotics (manufacturing) to see how they excel in delivering high torque, high load carrying capacity and repeatability of movement.   Toppling in a mount is primarily a function of geometry. Hence, the strain wave mount, under certain configurations  is as susceptible as any conventional mount, to toppling. We really shouldn't be surprised by that but it would be incorrect to hold its relative mass advantage as the problem.  If a mount's load (geometric) configuration places it outside its operational parameters then a counterweight is needed.  

Jim  

Since we know you have the proficiency badge for discussion on this subject:  Do you foresee the SW drive replacing the common [or garden] wormwheel and worm? 

Should we be expecting an up-scaling, in the near future, to mounts able to handle much heavier loads? Or is there some intrinsic limitation, in the SW drive, which will deny large refractor owners an inalienable right to equatorial mounting success? For instruments with large moments due to their weight distribution and considerably greater length?

[Rusted]

1 hour ago, CraigT82 said:

Interestingly there has been a couple of posts over on CN by visual guys using HD mounts who have resorted to hanging bags of rock from the tripod head to try to stabilise the rig and prevent tip over.

Which is where the turnbuckle and ground fixing comes in to replace the rocks. [For those unfortunate enough to live, image or observe, in an area devoid of such ready made ballast] My feeling is that there will soon be very expensive, probably gold anodized, commercial water bags to take over the task of providing stability for AW mountings. The bags being so lightweight they will not affect air travel costs to any great extent. Water, or some other inexpensive fluid, is fairly universally available. Though it is highly likely [IMO] that an expensive,  commercial  additive, will be seen as absolutely vital. To increase the viscosity of the said ballast bag. In the event of suffering high winds and/or earthquakes during long exposures. We may even see bulbous tripods, with waterproof legs, available from many of the major names. All made in China, of course. 

[wimvb]

3 hours ago, saac said:

I think you have hit on something here Olly with that observation.  I often find myself reflecting on the micro observatory built by @Skipper Billy considering it to be such an efficient and pleasing design.  The emergence of strain wave drives as a dominant mount design could well benefit these type of micro observatories. This could only be a positive consequence of the counterweight free feature making it an attractive solution where space is limited. 

Jim  

 

Just google "micro observatory" for more ideas. This one was presented/discussed a few years ago in the INDI forum.

[ollypenrice]

6 hours ago, Alan White said:

Thread drift for which I apologise.

Interesting block @ollypenrice, what are they solid or hollow?
Of course they will be a French block and available in blighty no doubt.
 

They are hollow and epoxy-bonded together and to the floor. A threaded bar set into the floor also passes up the middle and pulls the mount towards the floor, also binding the blocks together.

Olly

Edited August 12 by ollypenrice
typo

[GTom]

2 hours ago, Rusted said:

Since we know you have the proficiency badge for discussion on this subject:  Do you foresee the SW drive replacing the common [or garden] wormwheel and worm? 

Should we be expecting an up-scaling, in the near future, to mounts able to handle much heavier loads? Or is there some intrinsic limitation, in the SW drive, which will deny large refractor owners an inalienable right to equatorial mounting success? For instruments with large moments due to their weight distribution and considerably greater length?

I wasn't addressed but my £0.02 bet is that where MOBILITY is requred, SW will replace conventional CW'd GEMs rather soon. Just look at iOptron's CEM26 vs HEM15 pricing... 

[Elp]

16 minutes ago, GTom said:

HEM15 pricing...

I wouldn't read too much into this, when the hem15 was announced it was around 1500 on ioptrons website, ioptron quickly dropped the price once the am3 was revealed.

[GTom]

25 minutes ago, Elp said:

I wouldn't read too much into this, when the hem15 was announced it was around 1500 on ioptrons website, ioptron quickly dropped the price once the am3 was revealed.

Cem26 with steel tripod: £1230

HEM15 head only: £1159

No brainer imho. Going for the caron tripod will result in a slightly more expensive bill in exchange for a huge weight saving.

And of course, plenty of options now: am3, umi 17r, ragdoll 17, skywatcher 100i and so on.

Edited August 12 by GTom

[Elp]

I was referring more to how they come up with the prices to begin with, how could ioptron have knocked off 400-500 off the initial price just like that?

I agree, with the current prices, I'd err towards the HD, well I did.

[saac]

2 hours ago, Rusted said:

Since we know you have the proficiency badge for discussion on this subject:  Do you foresee the SW drive replacing the common [or garden] wormwheel and worm? 

Should we be expecting an up-scaling, in the near future, to mounts able to handle much heavier loads? Or is there some intrinsic limitation, in the SW drive, which will deny large refractor owners an inalienable right to equatorial mounting success? For instruments with large moments due to their weight distribution and considerably greater length?

Well I wouldn't be transfering my pension funds into the gold anodized plastic bag market yet Rusted.  

Jim

[Skipper Billy]

3 hours ago, wimvb said:

I often find myself reflecting on the micro observatory built by @Skipper Billy considering it to be such an efficient and pleasing design. 

Its had a wee update - the roof design required a rethink post major surgery - its now electrified and fully remote - https://www.davidbanksastro.com/observatory-conversion

 

[saac]

20 hours ago, Skipper Billy said:

Its had a wee update - the roof design required a rethink post major surgery - its now electrified and fully remote - https://www.davidbanksastro.com/observatory-conversion

 

I'd followed that Billy and well executed is is too. Your design/build is one of the most elegant and aesthetically pleasing observatories that I've seen. More than just good to look at, I think the design would support easier maintenance as it ages. The roof on my own observatory (based on an octagonal summer house) is quite heavy and I'm a little worried how easy it will be to maintain the structure through its life.

Jim 

Edited August 13 by saac