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Mount Jiggle with my 120mm F8.3

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#1 Chris1485

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Posted 06 July 2013 - 04:02 AM

Hi all,
I've just had first light with my new (second user) Skywatcher 120mm F8.3 Refractor.
The only problem was how the mount vibrated every time I touched it.
If I tapped the scope it jiggled for about 10 seconds!
It came with an EQ3 mount, which looks beefy enough.
Any advice for a stable AZ and EQ mount.

Thanks,

Chris (UK)

#2 Jon Isaacs

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Posted 06 July 2013 - 05:07 AM

Hi all,
I've just had first light with my new (second user) Skywatcher 120mm F8.3 Refractor.
The only problem was how the mount vibrated every time I touched it.
If I tapped the scope it jiggled for about 10 seconds!
It came with an EQ3 mount, which looks beefy enough.
Any advice for a stable AZ and EQ mount.

Thanks,

Chris (UK)


Chris:

I had a similar problem with an Orion 120mm F/8.3 mounted on the AstroView mount which is the same mount as the EQ-3. The problem was the tripod, the extruded aluminum legs were just not stiff enough. There are a variety of fixes... New tripod, wooden legs,

Jon

#3 SeattleScott

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Posted 06 July 2013 - 09:21 AM

A Celestron CG5 would be up to the task if you want a whole new mount. Not sure on the AZ side, maybe a twilight II? The ones that are both eq and az tend to be very heavy and fairly expensive.

#4 tomcody

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Posted 06 July 2013 - 09:33 AM

1. Make sure all the az and alt locks on the mount are tight.
( this one makes my mount vibrate every time I forget to tighten some thing)
2. Make sure all three legs are on a solid base.
3. lower the legs to see if that helps, if so? a stronger tripod my be needed.
4. try a heavier counter weight closer to the top of the shaft.
Rex

#5 PeterR280

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Posted 06 July 2013 - 09:35 AM

tripod legs make a big difference

#6 Chris1485

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Posted 06 July 2013 - 02:37 PM

Thanks for the replies.
I had wondered about wooden tripod legs. Any suggestions for a wooden tripod that isn't too expensive.
Would the EQ5 be much more solid and vibration free?
Also is the EQ5 alot heavier to carry?
I don't think the twilight mount is available in the UK. Even so it looks expensive.
I'll try making sure everything's tightened up and also an extra weight further up the counterweight shaft.

All good advice, thanks again,

Chris.

#7 PeterR280

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Posted 06 July 2013 - 04:44 PM

I have the newer CG5 with the large stainless legs and the mount is very stable. I don't notice too much vibration.

#8 KWB

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Posted 06 July 2013 - 06:00 PM

The EQ5 mount surely is more stable but comes at the price of being noticeably heavier to move outdoors. Fully assembled this setup would be a real chore for me. YMMV.

Like Jon stated above,an aftermarket wooden tripod would be a significant improvement for your present setup.

#9 Jon Isaacs

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Posted 06 July 2013 - 10:05 PM

I had wondered about wooden tripod legs. Any suggestions for a wooden tripod that isn't too expensive.



If you are handy with tools, you can build your own legs and attach them to your current tripod hub. They can be as simple as three pieces 2"x3" wood with cutouts to fit the tabs and holes for bolts.

My 120mm F/8.3 on the EQ-3 vibrated so badly that I had to turn the drives off, each tick of the stepper motor would cause a vibration so at 100x the image was a constant blur. I was lucky to have a very solid tripod (rated for 400 lbs) and it completely resolved the problem, no need for a CG-5...

Jon

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#10 Chris1485

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Posted 07 July 2013 - 03:45 AM

Thanks all for the ideas.
I think a different tripod is in order.
I'll look at the possibility of making one before I splash out on a commercially made one.

Your set up looks good Jon. I think it's best if the hieght can be adjusted.

I'm really impressed with the 120mm Achro so I'm keen to have a usable mount.

Thanks all again,

Chris.

#11 Jon Isaacs

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Posted 07 July 2013 - 05:37 AM

Your set up looks good Jon. I think it's best if the hieght can be adjusted.



It is very nice if the height can be adjusted but it makes the tripod considerably more complicated and more difficult to build. You could determine the optimal height with your current tripod and just make some legs based on that.

Jon

#12 Abb

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Posted 07 July 2013 - 09:49 AM

The Skywatcher EQ3 is the same as the Celestron CG4 (which I have) but I have the steel version - is yours steel or aluminum??? Anyway I have the Celestron version of your scope had had (and still get) similar vibration problems but not as bad as what you're describing.
1. Tighten everything as I found that made a noticeable difference.
2. I don't extend my legs as I bought a 16" Orion Pier Extension which not only saves my neck :) but adds stability to the tripod. Also my kid is into weight lifting and I found adding a couple of 5 LB (or if I'm ambitious 10 LB) weights to the Accessory Tray/Leg Brace also helps.
3. I found I get more vibration when I'm on concrete than I do when on grass - care to guess where I put my scope now?
4. However there are times when I have no choice and end up putting my scope on concrete. Commercial vibration pads do work cause I've seen them in action but they're too expen$ive so I tried making my own. I got some furniture coasters from the dollar store and extra felt and put them on the coasters. Surprisingly these home made el-cheapo vibration pads do help.

Hope all this helps you out - good luck!

#13 Scott Beith

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Posted 07 July 2013 - 09:57 AM

http://handsonoptics...&cPath=1_74&...

I have used this one in the past and it was excellent.

#14 Chris1485

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Posted 08 July 2013 - 04:24 AM

Thanks for yet more good advice.
I thinks for simplicity, Jon is right.
I'll try some home made solid legs, which, I think, should be quite easy for me to make.
Also the idea of Abb's to mount a pier extension is good.
Reduce the extension of the legs and add some ballast.
Also the anti-vibration pads is a great (cheap) idea.

I do tend to observe from my patio which is concrete. I may try the grass.

Eventually I think I'll invest in a wooden tripod.

Thanks again for the great advice.

Chris.

#15 Jon Isaacs

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Posted 08 July 2013 - 06:19 AM

I thinks for simplicity, Jon is right.
I'll try some home made solid legs, which, I think, should be quite easy for me to make.



Here's a photo of some I made from 2x2s for a 70mm but I recommend 2x3s for your scope. Definitely crude but they are effective.

I would be reluctant to use a pier with the aluminum legs. It would make the mount tippier, you need the legs spread out.

Jon

#16 Chris1485

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Posted 09 July 2013 - 04:19 AM

I thinks for simplicity, Jon is right.
I'll try some home made solid legs, which, I think, should be quite easy for me to make.



Here's a photo of some I made from 2x2s for a 70mm but I recommend 2x3s for your scope. Definitely crude but they are effective.

I would be reluctant to use a pier with the aluminum legs. It would make the mount tippier, you need the legs spread out.

Jon


Sorry Jon, I don't see your picture.

I took my EQ3 out yesterday evening, and mouted the 120mm to see if I could come up with an optimum length for some solid wooden legs.
Even though I like to observe sitting down and don't have an adjustable chair, I still managed to find a height that covers most of the sky while still being able to get my eye to the EP.

I measured the extension of the legs (1200mm). So I'm going to get some 2x3" timber cut and get them fixed up to the mount hub.

I'll keep you posted as to how it works out.

Thanks again,

Chris.

#17 Jon Isaacs

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Posted 09 July 2013 - 06:30 AM

Sorry Jon, I don't see your picture.


Sorry about that... these legs were made from 2x2s but I think 2x3 would be better for the EQ-3 mount. I used the spreader from the original mount.

Posted Image

Jon

#18 Chris1485

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Posted 09 July 2013 - 06:52 AM

Sorry Jon, I don't see your picture.


Sorry about that... these legs were made from 2x2s but I think 2x3 would be better for the EQ-3 mount. I used the spreader from the original mount.

Posted Image

Jon


Looks good. Many thanks for the imput, Jon, and all.

I'll post some pictures when I get my wooden legs set up.

All the best,

Chris.

#19 Chris1485

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Posted 15 July 2013 - 09:29 AM

Just thought I'd let you see the first set up of my newly constructed tripod legs.
They are 70mm x 45mm and 1300mm long.
I'm no carpenter so the cutouts for the tripod hub are a bit rough and ready, but put together they work fine and importantly reduce vibration time by half.
I think that a few minor adjustments may cut this down further.

Many thanks for all your advice,

Chris.

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#20 tomcody

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Posted 15 July 2013 - 09:37 AM

Chris,
I looks like you have square (90deg) cuts at the bottom of the legs. On Diskmount tripods, the legs are cut at an angle so they sit flat (and the edges rounded - maybe a 1/4" radius), they are very solid this way, you may want to finish your legs the same.
Also on the Yahoo Diskmount users forum, Tom has instructions for what kind of finish he uses on the legs, you may want to check it out.
Rex

#21 Jon Isaacs

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Posted 15 July 2013 - 09:57 AM

Chris,
I looks like you have square (90deg) cuts at the bottom of the legs. On Diskmount tripods, the legs are cut at an angle so they sit flat (and the edges rounded - maybe a 1/4" radius), they are very solid this way, you may want to finish your legs the same.
Also on the Yahoo Diskmount users forum, Tom has instructions for what kind of finish he uses on the legs, you may want to check it out.
Rex


It probably depends on the surface. Setup on grass, close to the ideal surface, the end cut probably doesn't matter much.

Jon

#22 Eddgie

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Posted 15 July 2013 - 10:14 AM

As mentioned, you may find it better to use a wood rasp to shape the ends, but that is maybe more cosmetic.

One thing that will help will be to put the eyepiece/accessory tray on to the spreader. This will improve the stiffness of the spreader a lot.

If your mount did not come with one, see if you can find a used one. Even if it doesn't help, it is still handy to have.

Of course you can make one too. Cut a wooden disk about 25cm in diameter and mark the hole positions for the thumb screws, drill holes, add some wingnuts and you are in business. If you can find a 1.25" hole saw (or slightly larger) you can drill some eyepiece holes yourself with an electric drill.

The next big improvement will come if you add a set of vibration suppression pads. These things work and work well.

I am happy that other people showed you how easy it is to make serviceable legs. The tripod legs are almost always the weak point in these small EQ mounts.

O

#23 Chris1485

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Posted 15 July 2013 - 10:50 AM

I had thought about finishing the bottom of the legs, but wasn't sure whether to taper them, so just to try it out I left them cut square.
I will look at the site Rex suggests.

Thanks,

Chris.






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