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Balancing a Large Refractor

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#1 JKAstro

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Posted 08 April 2020 - 10:00 AM

For those who have overcome the challenges of mounting a large refractor in the 5.5 to 6 inch range, have you found that adding weight towards the middle of the scope where it is mounted adds stability?  It seems to me that part of the problem with long scopes is that the mass is at the extreme ends with not much in the middle to anchor it.

 

Thanks,

JK



#2 Jeff L

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Posted 08 April 2020 - 10:19 AM

Balancing isn’t too bad, it’s the polar alignment that blows

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#3 PNW

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Posted 08 April 2020 - 10:42 AM

Living at 48 North, I call it Astronomy Yoga.


Edited by PNW, 08 April 2020 - 10:43 AM.

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#4 Astrojensen

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Posted 08 April 2020 - 10:53 AM

Balancing isn’t too bad, it’s the polar alignment that blows

Especially when you're doing it from the wrong end of the mount...

 

 

Clear skies!

Thomas, Denmark


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#5 Paul Hyndman

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Posted 08 April 2020 - 11:07 AM

For me it's not so much an issue with balance, but as an old geezer, it's becoming increasingly more challenging to (...oops!) hoist 'em up there.  gramps.gif

 

 

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#6 Astrojensen

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Posted 08 April 2020 - 11:43 AM

BTW, adding more weight to the middle of the scope will do absolutely nothing about the instability issues and just overload the mount (you also need more counterweight!)

 

What DOES help is to use more counterweight, so you don't have a weight sitting at the end of a long, thin stick. Getting a bigger, beefier mount saddle can also do wonders. The biggest improvement, however, often comes from upgrading the tripod. The 2" thin-walled stainless steel jobs you see on EQ-6/Atlas/CGEM class mounts simply doesn't cut it at all, when you have a 6" loaded. I upgraded to a Baader Hardwood tripod and the improvement was MASSIVE. It is, without any question, the easiest way to increase the carrying capacity of an EQ-6/Atlas/CGEM mount. 

 

gallery_55742_302_1407447647_23998.jpg

 

 

Clear skies!
Thomas, Denmark


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#7 25585

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Posted 08 April 2020 - 12:02 PM

Low centre of gravity helps. For sturdiness, a Berlebach Planet looks very strong. 



#8 bobhen

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Posted 08 April 2020 - 12:39 PM

Because they tend to be front heavy, triplets can pose a balance problem. Takahashi even offers a tube ring weight for their TOA models.

 

With my Takahashi TSA 120 and other triplets that I have owned, what I have done, in order to help move the tube forward in the rings, is add a third tube ring (and its associated weight) near the focuser. The ring adds weight to help counterbalance the triplet lens and it can also be used as an additional base to add finders etc.

 

Even with my old, long 152 F-9 triplet I never needed to add weight to the middle of the tube to help with stability.

 

Bob

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Edited by bobhen, 08 April 2020 - 12:39 PM.

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#9 macdonjh

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Posted 08 April 2020 - 12:45 PM

Balancing isn’t too bad, it’s the polar alignment that blows

Off topic, but may I suggest doing your polar alignment before you put your scope on your mount?


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#10 drd715

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Posted 08 April 2020 - 12:53 PM

BTW, adding more weight to the middle of the scope will do absolutely nothing about the instability issues and just overload the mount (you also need more counterweight!)

What DOES help is to use more counterweight, so you don't have a weight sitting at the end of a long, thin stick. Getting a bigger, beefier mount saddle can also do wonders. The biggest improvement, however, often comes from upgrading the tripod. The 2" thin-walled stainless steel jobs you see on EQ-6/Atlas/CGEM class mounts simply doesn't cut it at all, when you have a 6" loaded. I upgraded to a Baader Hardwood tripod and the improvement was MASSIVE. It is, without any question, the easiest way to increase the carrying capacity of an EQ-6/Atlas/CGEM mount.

gallery_55742_302_1407447647_23998.jpg


Clear skies!
Thomas, Denmark

The CGEM-DX tripod is a tank. Moded the spreaders 3 inches longer (slots milled into lower attach points for full folding) to widen the base footprint and use an 10 inch extension made from an expired scuba tank 5/8" wall thickness. Added a Starizona landing pad - all is good.

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#11 sunnyday

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Posted 08 April 2020 - 01:13 PM

Because they tend to be front heavy, triplets can pose a balance problem. Takahashi even offers a tube ring weight for their TOA models.

 

With my Takahashi TSA 120 and other triplets that I have owned, what I have done, in order to help move the tube forward in the rings, is add a third tube ring (and its associated weight) near the focuser. The ring adds weight to help counterbalance the triplet lens and it can also be used as an additional base to add finders etc.

 

Even with my old, long 152 F-9 triplet I never needed to add weight to the middle of the tube to help with stability.

 

Bob

which company does your right finder come from? thanks



#12 Jeff L

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Posted 08 April 2020 - 02:24 PM

Off topic, but may I suggest doing your polar alignment before you put your scope on your mount?

Polar alignment is simple it’s the two star that sucks . Besides it just a joke . It’s also daylight 


Edited by Jeff L, 08 April 2020 - 02:24 PM.

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#13 bobhen

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Posted 08 April 2020 - 03:05 PM

which company does your right finder come from? thanks

Stellarvue imports them (from China I believe) and they are sold through SV and by other retailers.

 

Bob


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#14 25585

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Posted 08 April 2020 - 04:13 PM

Because they tend to be front heavy, triplets can pose a balance problem. Takahashi even offers a tube ring weight for their TOA models.

 

With my Takahashi TSA 120 and other triplets that I have owned, what I have done, in order to help move the tube forward in the rings, is add a third tube ring (and its associated weight) near the focuser. The ring adds weight to help counterbalance the triplet lens and it can also be used as an additional base to add finders etc.

 

Even with my old, long 152 F-9 triplet I never needed to add weight to the middle of the tube to help with stability.

 

Bob

My set up is similar, 3 rings, but I use a long bar to attach all 3 to as extra OTA security generally. 



#15 Bomber Bob

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Posted 08 April 2020 - 04:40 PM

My 2017 APM 152ED is my largest & heaviest frac.  It's rock solid on my 1940s Tinsley Labs EQ.  But if you can't find one of those...  a vintage 1980s Meade StarFinder on a 5' pedestal does the trick:

 

APM ED 152 S071 (Tinsley Mount).jpg APM ED 152 S076 (Meade SF Restore).jpg

 

The 16" long mount plate spreads out the load, and my 1983 Tak FC-50 on Bresser rings puts the eyepiece up at a comfortable observing height; otherwise, this nose-heavy OTA would be near ground level.


Edited by Bomber Bob, 08 April 2020 - 04:41 PM.

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#16 drd715

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Posted 08 April 2020 - 04:52 PM

My set up is similar, 3 rings, but I use a long bar to attach all 3 to as extra OTA security generally.

I also use a 3rd ring and a long MDS (ADM) top bar to mount the long guider scope more aft in position than centered.

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#17 stevew

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Posted 08 April 2020 - 07:41 PM

I'm not sure adding weight to the middle of the tube would do anything.

When it's windy I just add a Hargreaves strut.

 

 

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#18 drd715

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Posted 08 April 2020 - 09:39 PM

And i see every long scope has a Telrad.

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#19 beanerds

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Posted 08 April 2020 - 10:02 PM

The CGEM-DX tripod is a tank. Moded the spreaders 3 inches longer (slots milled into lower attach points for full folding) to widen the base footprint and use an 10 inch extension made from an expired scuba tank 5/8" wall thickness. Added a Starizona landing pad - all is good.

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It's almost exactly what I did to my 6 inch f8 , I also epoxied about 3 pounds of lead fishing sinkers into the focuser adapter , its a great scope especially with it's Chromocor fitted .

 

Beanerds

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#20 Wildetelescope

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Posted 11 April 2020 - 07:22 AM

A g11gt on a 54 inch high parallax pier does the job with my 6inch f9. Can sit in my chair and view comfortably at zenith. Solid as the rock of Gibraltar.

Jmd


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