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Walking on the Moon

Mount stability


jacksdad
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Some of you may remember a while back I had a play with an eq3-2 (holding a sw 150pl) to see if I could improve it.

 

Well, it got better, so that was a start.

 

But what is considered a reasonable time to damp down vibration following contact (moving the ota, focusing, accidentally nudging the counterweight shaft...)?

 

I currently get a solid view after about 1.5 seconds following a nudge (less after a gentle touch like focusing, like maybe a second). Certainly way better than the 8-10+ seconds fitted as standard.

 

I find it a little frustrating as it makes the action of focusing take longer than I think it should (motor focuser project incoming).

 

So, what is considered good?

 

I'd like no wobble/vibration at all if I'm honest, but maybe that's actually unobtainable anyway...

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When I used an EQ2 to hold my 130/900 newt, it never stopped wobbling. Nearly put me off EQ mounts all together.

My 250px dob wobbles a fair bit but is relatively stable when pointing higher up, bit stiff when lower down. Maybe average 1s to stop worst wobble?

My HEQ5 is a rock. Even on a wobbly floor i can basically punch it and it stops wobbling in half a second with my 130-pds on it.

I'd say for visual 1.5s is decent. Photography maybe less so but still good for short exposures provided there's no wind. I find focusing needs a "feather touch" on most if not all mounts.

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1 hour ago, jacksdad said:

I'd like no wobble/vibration at all if I'm honest, but maybe that's actually unobtainable anyway...

Not if you throw money at it. In my case the improved eq3 (pro) is called AZ-EQ6. :grin:

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While throwing money at it may well resolve the issue, that's simply not an available option.

 

So, I'll throw other stuff at it instead ;)

 

As I mentioned in the other thread on the subject, I think part of the issue is the length of the OTA on this mount - with smaller scopes (like my skymax 102) or a DSLR and 500mm telephoto lens it just doesn't move. Anything short of knocking it over doesn't seem to phase it much at all.

 

The only bits I haven't put much into yet are the alt pivot (where tbf I can feel a little movement) and the tripod leg mounts (plastic on this, I'm sure that's not helping).

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3 hours ago, jacksdad said:

While throwing money at it may well resolve the issue, that's simply not an available option.

It wouldn't have been for me either (at least not the AZ-EQ6), if it hadn't been for Brexit.

3 hours ago, jacksdad said:

So, I'll throw other stuff at it instead ;)

So did I. The problem is that the tripod is much less portable if it's filled with sand. There's a trade off between stability and portability. There are also so many holes for sand to run through, that I didn't consider thus to be a good solution. And as you already noted, the small self tapping screws of the spreader are becoming a serious risk. So, this is how I solved it. The dowels are fixed inside the legs by the plastic endpieces.

lowerleg.jpg.1fefc9c28887d233eafdac88cd1df8af.jpgupperlegdetail.thumb.jpg.012ae8435ba4426871c9f9a7fe332559.jpg

 

Edited by wimvb
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9 minutes ago, wimvb said:

It wouldn't have been for me either (at least not the AZ-EQ6), if it hadn't been for Brexit.

So did I. The problem is that the tripod is much less portable if it's filled with sand. There's a trade off between stability and portability. There are also so many holes for sand to run through, that I didn't consider thus to be a good solution. And as you already noted, the small self tapping screws of the spreader are becoming a serious risk. So, this is how I solved it. The dowels are fixed inside the legs by the plastic endpieces.

lowerleg.jpg.1fefc9c28887d233eafdac88cd1df8af.jpgupperlegdetail.thumb.jpg.012ae8435ba4426871c9f9a7fe332559.jpg

 

Ingenious solution, does it help?

I find I am content when vibrations damp in under a second, more than that and it gets a little frustrating.

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13 minutes ago, Stu said:

Ingenious solution, does it help?

Since I got the AZ-EQ6, I mainly use that at home with the 150pds, and the eq3 away from home with a lightweight imaging solution (pentax dslr + 135 mm lens). There haven't been many clear nights to use it, really. But my impression when I did the mod was, that it's more stable and that it reduces vibrations.

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34 minutes ago, wimvb said:

So did I. The problem is that the tripod is much less portable if it's filled with sand. There's a trade off between stability and portability. There are also so many holes for sand to run through, that I didn't consider thus to be a good solution. And as you already noted, the small self tapping screws of the spreader are becoming a serious risk. So, this is how I solved it. The dowels are fixed inside the legs by the plastic endpieces.

I've had the sand in all 9 leg sections for nearly a year and none has escaped - the sealant I used (and how I applied it) seems to have worked just fine.

 

Portability isn't a huge issue in itself, it only really gets used at home so through the house to front or back garden is as far as it normally travels, and there's a way to go yet before I consider it too awkward to transport (anything up to around 30kg or so is one hand carry depending on shape, and a folded and strapped tripod is an easy shape).

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8 minutes ago, jacksdad said:

I've had the sand in all 9 leg sections for nearly a year and none has escaped - the sealant I used (and how I applied it) seems to have worked just fine.

I didn't have a proper sealant handy when I did my mod, plus I wanted it to be reversible in case it didn't work. And as I had some oak and hardwood dowels lying around, I went with that. I think that your decision to replace the small spreader screws is also a good one. With the increased weight, the original screws could very well tear through the aluminium legs.

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4 hours ago, wimvb said:

I didn't have a proper sealant handy when I did my mod, plus I wanted it to be reversible in case it didn't work. And as I had some oak and hardwood dowels lying around, I went with that. I think that your decision to replace the small spreader screws is also a good one. With the increased weight, the original screws could very well tear through the aluminium legs.

Fair enough, I wasn't judging ;)

It's kind of part of my job to have this sort of stuff to hand most of the time, and if I wanted to undo it I can use sealant remover so no harm.

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18 hours ago, Roy Challen said:

I had a similar situation a few years ago, here's a link to what I did. I now have a much heavier mount but would still like a concrete pier. 

 

 

 

 

There's a comment in that thread about loosening the top leg bolts which does highlight the different interpretations of 'stabilty'...

 

With what I've done to the tripod and mount I have it stable - put it down and it stays there. There's very very little flex.

 

But, it's still got some 'spring' to it.

 

Slacken off the top bolts and the vibrations absolutely disappear, but it's not stable.

 

More consideration required.

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32 minutes ago, wookie1965 said:

Look for a HEQ5 tripod it fits the EQ3-2 mount make it much stabler. I know it fits as I did that with mine. 

I honestly don't think that'll make any difference to the problem I'm experiencing. Compared to a standard aluminium tripod I could see a huge improvement, but 'mine' (my son's) isn't standard.

 

The tripod itself is perfectly stable (what with having steel tubes and well tamped sand inside the aluminium sections).

 

The vibrations and time to settle are in the mount itself (I can measure this) due to 'spring' - I reckon I could bolt it to a concrete pier and not see much/any difference, if anything it might actually be worse.

 

I personally think damping is the answer now.

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I used sand in mine and hung a weight from the spreader plate it was only after I purchased the HEQ5 tripod I got steadier views.

If you want something to help dampen down the mount these may be of use.

https://www.ebay.co.uk/itm/Opticstar-Heavy-Duty-Vibration-Suppression-Pads-UK/322469101576?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649

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The best way to dampen the mount is to avoid vibrations as much as possible. I think that motor focuser you mentioned earlier is a natural next step. I have the sw motor focus, but the battery is a bit weak in cold weather.

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3 hours ago, wookie1965 said:

I used sand in mine and hung a weight from the spreader plate it was only after I purchased the HEQ5 tripod I got steadier views.

If you want something to help dampen down the mount these may be of use.

https://www.ebay.co.uk/itm/Opticstar-Heavy-Duty-Vibration-Suppression-Pads-UK/322469101576?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649

Something like that might not be a bad idea - I have some similar material so worth an experiment.

 

55 minutes ago, wimvb said:

The best way to dampen the mount is to avoid vibrations as much as possible. I think that motor focuser you mentioned earlier is a natural next step. I have the sw motor focus, but the battery is a bit weak in cold weather.

I've got enough bits to cobble a focus motor and as that's the main source of nuisance vibration it's got to be worth a go.

 

I think after that I'll be looking at powering the mount axis, not necessarily to track (although basic short term tracking should be relatively straightforward) but more for positioning.

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