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Orange C8 Ringing

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#1 Tom Stock

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Posted 05 March 2015 - 11:10 PM

I have an Orange C8, beautiful scope, but the aluminum tripod was terrible. Very wobbly mess.  I replaced the tripod with a Celestron Heavy Duty Field Tripod. It has 2" dia steel legs, extremely heavy duty castings.  Very nice and solid tripod.  So after replacing the tripod, I found the overall amplitude of vibration was greatly decreased, however the RINGING has nearly doubled.  After focusing I must wait 9 seconds... and a sharp rap on the fork resonates for an excruciating 17 seconds!  I can feel no vibration in the mount while it's ringing, only at the fork.

 

The only thing which stops the ringing is to grab both forks, or push up firmly on the fork housing... does not seem to be the wedge or tripod which is ringing.

 

Any ideas for a fix?

 


Edited by Tom Stock, 07 March 2015 - 11:17 PM.


#2 orion61

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Posted 08 March 2015 - 09:23 PM

When the RA is locked and motor is off, is there a little play in the fork drive? I mean just a bit or is it tight?

If one motor is out of gear phaze with the other it can cause this. I can help you fix it but will require some

tear down of the drive. I hae worked on about 100 of these systems.

try unlocking the RA cluch and tapping, does the ring go away?

Duane



#3 Tom Stock

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Posted 08 March 2015 - 10:41 PM

Hi Duane, thanks for the reply. No the ring doesn't go away when I unlock the RA. The ring I'm referring to isn't something happening while tracking.

 

I guess I should explain what I mean by the "ring".  It's like a tuning fork. It runs perfectly quiet and smooth, tracking is great. But if I give the fork a light smack, or even touch the focuser and let go, it takes a long time for the scope to settle down (regardless of whether it's running or unplugged).  By long I mean 9 to 20 seconds :(  That is what I would expect of a department store scope not my beloved orange C8.

 

This is typical behavior of a fork hanging off a wedge, so I am not necessarily surprised... my LX90 did the same thing, but not for 20 seconds.  I'm just wondering if there is a way to dampen the ringing.  I've tried reinforcing the wedge with no improvement.  There is a possibility it could be the wedge plate itself (the tilted plate) flexing.  I do have an idea for stiffening that part up.

 

Failing that, I could switch to a wooden heavy duty tripod. Perhaps it's flex (but natural dampening quality) may help reduce this tuning fork situation!

 

This started when I switched from the wobbly aluminum tripod to an ultra stiff steel tripod, so it's pretty clear what the problem is, but I am hoping to find a way to dampen the vibration without giving up this beautiful field tripod.


Edited by Tom Stock, 08 March 2015 - 10:44 PM.


#4 Brian Risley

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Posted 09 March 2015 - 07:19 AM

Have you tried the vibration pads.

I find they do make a difference and can help vibrations dampen out faster.

Brian


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#5 Joe Cepleur

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Posted 10 March 2015 - 08:28 PM

It used to be that, when the fork vibrated, the tripod absorbed its motion. Now, the vibration is held in the fork. Try stuffing towels or pillows around the fork. Never mind whether this leaves the scope useable; just see whether it absorbs the vibration.

The stiffer steel tripod does not absorb the vibration,

#6 Tom Stock

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Posted 11 March 2015 - 09:40 PM

Actually with some further investigating, the vibration seems to be the wedge.  I can feel the RA mounting plate flexing. I think some turn buckles, and tying the end of the wedge into the legs with tensioned cables will dampen the vibration.



#7 Geo31

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Posted 11 March 2015 - 11:17 PM

http://www.ngc1514.c...estron/tips.htm

 

Scroll down to the bottom.....



#8 Tom Stock

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Posted 12 March 2015 - 07:16 PM

Ahah! Thanks! Funny I was thinking about something similar to this last night but hadn't quite finished the idea in my head.  Looks like someone else did!



#9 Geo31

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Posted 12 March 2015 - 07:54 PM

I don't have anything to give you except gut feel, but I think the vibrations of a C8 on a wedge and tripod are likely due to the wedge.  You're basically hanging a large, long, and heavy moment arm off the wedge and stabilizing it from the opposite "pole" should work wonders.  I have some ideas for making a more stable wedge, but that is going to have to wait a bit.


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#10 smeyer8015  Happy Birthday!

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Posted 12 March 2015 - 08:26 PM

I have an early 90's Classic 8 that suffered from long vibration times after touching the focus knob. It took almost 10 seconds to stop.

I had a set of old turntable vibration damping feet. Put one under each leg of the tripod. The vibration was change to a slow wobble that only lasts a second or two.

Id say a set of vibration dampers are in your future.

 

Scott


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#11 Tom Stock

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Posted 13 March 2015 - 04:09 PM

Scott, did you use these pads in the grass or on a solid surface?

 

Thanks



#12 orion61

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Posted 13 March 2015 - 07:13 PM

It is the wedge AND fork combination, I took a Meade wedge and marked and drilled holes for my Celestron. It is still usable for both scopes but did not get rid of all the settle down time. It did cut it down to about 1/2. This is the reason for the massive forks and different Wedge on the redesigned Ultima series in 1987.

I also took a sheet of Cork and put between the wedge bottom and tripod. Anything over 5-7 seconds is a real pain,

A "Kwik Focus" front cover helps with fine focus, it has 3 small circles cut into a corrector cover that focus down to one.

a Motorized focus and drive corrector helps a lot too.



#13 Geo31

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Posted 13 March 2015 - 07:20 PM

It is the wedge AND fork combination, I took a Meade wedge and marked and drilled holes for my Celestron. It is still usable for both scopes but did not get rid of all the settle down time. It did cut it down to about 1/2. This is the reason for the massive forks and different Wedge on the redesigned Ultima series in 1987.

I also took a sheet of Cork and put between the wedge bottom and tripod. Anything over 5-7 seconds is a real pain,

A "Kwik Focus" front cover helps with fine focus, it has 3 small circles cut into a corrector cover that focus down to one.

a Motorized focus and drive corrector helps a lot too.

 

How did the cork work out Duane?  I've thought of something similar.


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#14 Tom Stock

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Posted 13 March 2015 - 09:35 PM

I once had an LX90 on a standard wedge, and I cut an eyepiece tray out of 3/4" birch ply.  I placed it between the wedge and tripod, and through bolted it to the bottom of the wedge.  Surprisingly there was no improvement.   I upgraded to the super wedge which was rediculously overbuilt... and somewhat better.

 

So... thinking back bout this, I just placed two straps on the south corners of my C8 wedge and tightened them down.  Guess what, no improvement! Hmm!

 

So, I moved the strap to the top mounting bolt of the RA mounting plate.  I tightened it down, and whalla! It settles down in 2-3 seconds!

 

Now looking at my C8 mount, I think I understand why.  It's not the wedge itself flexing, but the mounting plate flexing.  If you look at it, the pivot point of the RA plate is 1/3 off center, so the whole plate is springing like a diving board.

 

This is why the wood attached to the back of this plate, and then attached to a lead weight (referenced above) made such an improvement... because it's dampening the RA mounting plate, not the wedge body itself.

 

Well that's my theory anyway.


Edited by Tom Stock, 13 March 2015 - 09:38 PM.


#15 smeyer8015  Happy Birthday!

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Posted 13 March 2015 - 09:36 PM

Scott, did you use these pads in the grass or on a solid surface?

 

Thanks

Both. Makes a bigger difference on hard surfaces.

 

Scott



#16 TCW

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Posted 13 March 2015 - 10:22 PM

If this were my scope I would try filling the tripod legs with some sort of foam to help dampen vibrations.



#17 Vesper818

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Posted 13 March 2015 - 10:52 PM

C8s ring, are you listnin'?
Up above,stars are glistenin'
A beautiful sight,
We're happy tonight
Slewing though a stellar wonderland..
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#18 TOM KIEHL

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Posted 14 March 2015 - 08:31 AM

C8s ring, are you listnin'?
Up above,stars are glistenin'
A beautiful sight,
We're happy tonight
Slewing though a stellar wonderland..

 

 

:rollingeyes:  good one :applause: :lol:


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#19 Tom Stock

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Posted 14 March 2015 - 05:07 PM

I just replaced the RA plate with a 3/4" MDF plate I cut on my CNC machine, but lowered the plate 2".  So instead of the plate pivot being at the lower 1/3 point, it's above 1/2 way point, so most of the telescope is mounted below the pivot point.  This plate probably wouldnt work below Florida... I lowered it enough so that the scope and fork barely clears the tripod. I'm at 28'.

 

But guess what? It settles in 1.4 seconds instead of 17 seconds.  I'm sort of stumped as to why anyone would make a diving board for a mounting plate.

 

I'll be machining one from Aluminum this week. If the Aluminum version works I may make a few more of these if anyone wants one.

 

;)

 

Below you can see a before (aluminum mounting plate) and after (MDF mounting plate). See how much lower the MDF plate is mounted?

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Edited by Tom Stock, 14 March 2015 - 06:11 PM.

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#20 Geo31

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Posted 14 March 2015 - 06:04 PM

TOM!!!  This is exactly what I've had in mind!

 

To my eyes, the stock wedge really hangs everything out way further than necessary.  I want to bring everything in much tighter.  When you think of it, the OTA is attached to a long moment arm (the forks) and then the stock wedge places the whole deal on yet another unnecessarily long moment arm. 

 

If you would be willing to machine a second RA plate, please PM me the cost.  I'm VERY interested.  I'm a 30' so it would work great for me.



#21 Tom Stock

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Posted 14 March 2015 - 06:12 PM

Ok will do. Let me get the Aluminum version cut, and if it still works as well as the MDF plate, I'll make another for you!



#22 Geo31

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Posted 14 March 2015 - 10:48 PM

Many many thanks Tom!



#23 Tom Stock

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Posted 15 March 2015 - 06:23 PM

Well, I did get a chance to use the mount last night with the new plate.  A sharp rap on the tube settles in 3 seconds.  Touching the focuser settles in about 1 second, so that is a huge improvement.

 

I don't expect an aluminum plate to work as well as the MDF plate, but it's worth a try. 

 

I grabbed this quick photo of Jupiter with my C8.

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Edited by Tom Stock, 15 March 2015 - 06:24 PM.

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#24 Geo31

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Posted 15 March 2015 - 06:45 PM

Nothing wrong with MDF if it gets sealed properly.

 

I wonder if there is another readily available material that will damp the vibrations as well that would not be so sensitive to moisture.

 

Did you use brass inserts  where the knobs screw in?



#25 Tom Stock

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Posted 15 March 2015 - 08:04 PM

Nothing wrong with MDF if it gets sealed properly.

 

I wonder if there is another readily available material that will damp the vibrations as well that would not be so sensitive to moisture.

 

Did you use brass inserts  where the knobs screw in?

 

No, I didn't, it was just a quick test.  I drilled and tapped holes and then hardened the threads with CA glue. It didn't work well, the threads stripped when I tightened the plate down, but the plate did make it through the night.  The problem with MDF is it delaminates easily and splits, so I would not trust hanging a scope on it for long.

 

Sealed oak or bamboo with threaded inserts would probably work well.




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