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Balancing Problem CEM60 w/Videos

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#1 Monkeybird747

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Posted 12 June 2018 - 08:45 PM

Chasing my tail on a balance problem with my imaging rig. I have everything up on the scope to take advantage of the through-the-mount cable system. Couple of videos below to show my problem.

 

I balanced in RA and Dec horizontal and then noticed the scope does this in Dec with mount in the zero position:

 

https://www.dropbox....G_0561.MOV?dl=0

 

So I moved the RDF to the opposite side, and added a small amount of counter weight near the focus control box. So then I got this. Nice!

 

https://www.dropbox....G_0565.MOV?dl=0

 

But when I released the RA clutch, this happened. Not nice!

 

https://www.dropbox....G_0566.MOV?dl=0

 

Here another shot of Dec balanced with RA horizontal:

 

https://www.dropbox....G_0567.MOV?dl=0

 

So I'm in a bit of a pickle. I can remove the small counterweight (taped together washers) and get RA balanced where it doesn't fall off to the west, but if I do that then the objective end of the scope falls off to the east as in the video above (with mount in zero position). To me its pretty clear I have more weight on the west side of the OTA (focus motor, controller, and RDF). So I'm not sure why I needed even more weight on that side to keep the dec from swinging the objective end off to the east.

 

I've had an endless stream of equipment issues (the latest was a failure of my new digifire 12 requiring new circuit board). Very little time under the stars this year, and I'm fighting off frustration the best I can. I feel like I've got this rig close to where I can image pretty happily for a while, but this balance thing is driving me crazy. If i can't get both perfectly balanced, which one should I pick?

 

BTW, I have more counterweights coming tomorrow to get the weight further up the bar. I have about 32lbs on the saddle right now.


Edited by Monkeybird747, 12 June 2018 - 09:16 PM.


#2 bmhjr

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Posted 12 June 2018 - 09:19 PM

I got a bolt and fender washers and attach to the hole on the side of the counter weight to add a bit more weight at an offset. You can then adjust the angle so everything comes to balance. It takes some trial an error but works. What drives me nuts, if I rotate the focuser for framing it is out of wack again.

#3 Monkeybird747

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Posted 12 June 2018 - 09:45 PM

I got a bolt and fender washers and attach to the hole on the side of the counter weight to add a bit more weight at an offset. You can then adjust the angle so everything comes to balance. It takes some trial an error but works. What drives me nuts, if I rotate the focuser for framing it is out of wack again.


Interesting. I can probably give this a try.

#4 HxPI

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Posted 12 June 2018 - 10:50 PM

It took me years before I finally figured out how to get my CEM60 to achieve perfect balance.... it was a beautiful sight to behold!

 

Looks like you found the Dec balance. The RA looks like it may need some east bias once the CWs are positioned properly. I use a photo clamp around the RA axis and the small CW bar with 3/8” threads that come with the iOptron SkyTracker CW kit to give the mount east bias. Seems to work for getting proper balance. I think the ultimate goal is to get some washers and put them in the proper places on the scope to properly offset the front/back and left/right balance of the scope on the saddle. This method would also allow changing out the imaging train without moving the scope or CWs. Just reposition the washers where necessary. This should work in theory at least....

 

Ciao,

Mel


Edited by HxPI, 12 June 2018 - 10:55 PM.


#5 Salty_snack

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Posted 12 June 2018 - 10:55 PM

In none of those videos is the telescope so out of balance that it matters. You are making it out to be more than it is.

But it is kind of a crime to run a dslr on that telescope.

#6 AntMan1

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Posted 12 June 2018 - 11:25 PM

Chasing my tail on a balance problem with my imaging rig. I have everything up on the scope to take advantage of the through-the-mount cable system. Couple of videos below to show my problem.

 

I balanced in RA and Dec horizontal and then noticed the scope does this in Dec with mount in the zero position:

 

https://www.dropbox....G_0561.MOV?dl=0

 

So I moved the RDF to the opposite side, and added a small amount of counter weight near the focus control box. So then I got this. Nice!

 

https://www.dropbox....G_0565.MOV?dl=0

 

But when I released the RA clutch, this happened. Not nice!

 

https://www.dropbox....G_0566.MOV?dl=0

 

Here another shot of Dec balanced with RA horizontal:

 

https://www.dropbox....G_0567.MOV?dl=0

 

So I'm in a bit of a pickle. I can remove the small counterweight (taped together washers) and get RA balanced where it doesn't fall off to the west, but if I do that then the objective end of the scope falls off to the east as in the video above (with mount in zero position). To me its pretty clear I have more weight on the west side of the OTA (focus motor, controller, and RDF). So I'm not sure why I needed even more weight on that side to keep the dec from swinging the objective end off to the east.

 

I've had an endless stream of equipment issues (the latest was a failure of my new digifire 12 requiring new circuit board). Very little time under the stars this year, and I'm fighting off frustration the best I can. I feel like I've got this rig close to where I can image pretty happily for a while, but this balance thing is driving me crazy. If i can't get both perfectly balanced, which one should I pick?

 

BTW, I have more counterweights coming tomorrow to get the weight further up the bar. I have about 32lbs on the saddle right now.

Bmhjr is correct. Take a look at this video when you get a second..I dont blame you wanting perfect balance & i hope you get it.     https://www.youtube....h?v=X8w77MrpB3o


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#7 scadvice

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Posted 13 June 2018 - 12:14 AM

I didn't look back at your posts, but did you level your tripod? It appears to act like the tripod is not level or the mount is not fully secured on the tripod???



#8 bobzeq25

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Posted 13 June 2018 - 12:26 AM

Can't help.  My setup is a little more symmetrical, I never try for exact balance, just go a bit camera heavy and East heavy.  Not much, just the margin of error, really. 



#9 Monkeybird747

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Posted 13 June 2018 - 07:24 AM

But it is kind of a crime to run a dslr on that telescope.


One thing at a time 😜. Committed to this for now. Mono cam will be next year’s project.
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#10 Monkeybird747

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Posted 13 June 2018 - 07:47 AM

I didn't look back at your posts, but did you level your tripod? It appears to act like the tripod is not level or the mount is not fully secured on the tripod???


Thats a good point, but I did double check this.

#11 Real14

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Posted 13 June 2018 - 07:57 AM

Hi,

 

Yes, balancing is Art ... waytogo.gif and this is what I had to balance on a CEM 120

 

IMG_3783_C1_CN.jpg

 

The only thing I can recommend you is

 

GET RID of those long cables. Copper is heavy lol.gif and in USA you find any adequate cable length and it will also make you cabling more easier to overlook.

 

Rainer


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#12 Monkeybird747

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Posted 13 June 2018 - 08:01 AM

AntMan1, that video is exactly what I needed! I believe it depicts what bmhjr and HxPI are describing. I need something on the counterweight bar at a right angle on the east side. I’ll start looking for a way to attach some washer weight. The C clamp he uses isn’t very elegant, but it works. That looks like a heck of a payload!

Also, his body language is a lot like mine in that video. It seems to be quietly saying “come on, you sonofa.....”.
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#13 Monkeybird747

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Posted 13 June 2018 - 08:10 AM

Hi,

Yes, balancing is Art ... waytogo.gif and this is what I had to balance on a CEM 120

IMG_3783_C1_CN.jpg

The only thing I can recommend you is

GET RID of those long cables. Copper is heavy lol.gif and in USA you find any adequate cable length and it will also make you cabling more easier to overlook.

Rainer


Yowzers!! That’s a beast!

I did get a shorter serial cable for the reasons you mention. I can probably shorten up some of the others too. Thanks!
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#14 HxPI

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Posted 13 June 2018 - 08:25 AM

AntMan1, that video is exactly what I needed! I believe it depicts what bmhjr and HxPI are describing. I need something on the counterweight bar at a right angle on the east side. I’ll start looking for a way to attach some washer weight. The C clamp he uses isn’t very elegant, but it works. That looks like a heck of a payload!

Also, his body language is a lot like mine in that video. It seems to be quietly saying “come on, you sonofa.....”.

I use the RRS Multi-Clamp. It is much nicer looking and fits well around the CEM60 RA axis hub where the CW connects.



#15 Monkeybird747

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Posted 13 June 2018 - 09:13 AM

HxPI, do you have a pic of how you are using it?

#16 Real14

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Posted 13 June 2018 - 09:31 AM

Yowzers!! That’s a beast!

I did get a shorter serial cable for the reasons you mention. I can probably shorten up some of the others too. Thanks!

You are welcome. I have to order the cables in USA because in Mexico I do not find them and if I find them they three times as waht I pay in USA including shipping undecided.gif

 

Those are 76 lbs of telescopes, cameras and accessories and 112 lbs of counterweights (Crafted with Pride in Mexico) lol.gif They are made of Aztec Gold lol.gif


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#17 bmhjr

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Posted 13 June 2018 - 11:41 AM

AntMan1, that video is exactly what I needed! I believe it depicts what bmhjr and HxPI are describing. I need something on the counterweight bar at a right angle on the east side. I’ll start looking for a way to attach some washer weight. The C clamp he uses isn’t very elegant, but it works. That looks like a heck of a payload!

Also, his body language is a lot like mine in that video. It seems to be quietly saying “come on, you sonofa.....”.


My 9.5 kg counterweight from iOptron has a threaded hole for this purpose. Sorry I dont remember the thread size.

Edit: the thread is M12-1.75 https://www.cloudyni...icks/?p=6063021

Edited by bmhjr, 13 June 2018 - 11:55 AM.


#18 HxPI

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Posted 13 June 2018 - 11:48 AM

HxPI, do you have a pic of how you are using it?

Here is one where you can see the clamp on the RA axis and the CW attached to the east side.

 

This is an older pic and the bias CWs are positioned incorrectly. I have removed one and placed the other one closer to the RA axis. You only need a small amount of bias weight. Having two was too much!

 

I would have used the string method, which I think is a better solution, but the CEM60s are not designed to support this method.

 

Hope this helps.

Attached Thumbnails

  • _20171021_095348.jpg

Edited by HxPI, 13 June 2018 - 11:57 AM.

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#19 Real14

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Posted 13 June 2018 - 12:11 PM

Hi,

 

I would have used the string method, which I think is a better solution, but the CEM60s are not designed to support this method.

It is not about not designed for it because the iOptron mounts do not have backlash at all. Applying an additional force on a worm would be nonsense and be counterproductive in this case.

 

The string method was invented for taking out the backlash on Losmandy Mounts as they did not have a spring loaded worm until a few weeks ago which is now offered by Losmandy bow.gif

 

Thirteen and a half years later after I had all my Losmandy modified with floating worm systems lol.gif

 

Rainer



#20 HxPI

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Posted 13 June 2018 - 12:29 PM

Hi,

 

It is not about not designed for it because the iOptron mounts do not have backlash at all. Applying an additional force on a worm would be nonsense and be counterproductive in this case.

 

The string method was invented for taking out the backlash on Losmandy Mounts as they did not have a spring loaded worm until a few weeks ago which is now offered by Losmandy bow.gif

 

Thirteen and a half years later after I had all my Losmandy modified with floating worm systems lol.gif

 

Rainer

Oh so there is no need for east bias on the iOptron CEM60?? Never knew that was the case. If that's the case, then I'll make sure to do regular balance from now on.

 

Thanks for sharing.


Edited by HxPI, 13 June 2018 - 12:30 PM.


#21 Monkeybird747

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Posted 13 June 2018 - 12:49 PM

Here is one where you can see the clamp on the RA axis and the CW attached to the east side.

This is an older pic and the bias CWs are positioned incorrectly. I have removed one and placed the other one closer to the RA axis. You only need a small amount of bias weight. Having two was too much!

I would have used the string method, which I think is a better solution, but the CEM60s are not designed to support this method.

Hope this helps.


That looks nice. I like your power box too.

#22 Monkeybird747

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Posted 13 June 2018 - 12:51 PM

Oh so there is no need for east bias on the iOptron CEM60?? Never knew that was the case. If that's the case, then I'll make sure to do regular balance from now on.

Thanks for sharing.


I was curious about this too since you are able set the amount of worm mesh.

#23 Real14

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Posted 13 June 2018 - 03:13 PM

Hi HxPI,

 

 

 

Oh so there is no need for east bias on the iOptron CEM60?? Never knew that was the case. If that's the case, then I'll make sure to do regular balance from now on.

 

Thanks for sharing.

How did you come up with the idea that a floating spring loaded worm/wormgear mechanism needs East Heavy balancing ?

 

A worm/wormgear mechanism with NO backlash needs to be nearly perfectly balanced ...

 

It is even worse to load a NON backlash system with weight to one side as you are increasing unnecessarily the friction on the worm/wormgear system

 

A worm/wormgear mechanism with BACKLASH needs the East/West heavy balancing in order to not to show the BACKLASH. BTW East/West heavy balancing looses its effectiveness the closer the CW comes to a vertical position and that is why the string trick (which BTW was invented by me for the Losmandy GM-8 and G11 mounts) worked much better as the unbalancing amount was always the same ...

 

Rainer



#24 HxPI

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Posted 13 June 2018 - 04:24 PM

Hi HxPI,

 

How did you come up with the idea that a floating spring loaded worm/wormgear mechanism needs East Heavy balancing ?

 

A worm/wormgear mechanism with NO backlash needs to be nearly perfectly balanced ...

 

It is even worse to load a NON backlash system with weight to one side as you are increasing unnecessarily the friction on the worm/wormgear system

 

A worm/wormgear mechanism with BACKLASH needs the East/West heavy balancing in order to not to show the BACKLASH. BTW East/West heavy balancing looses its effectiveness the closer the CW comes to a vertical position and that is why the string trick (which BTW was invented by me for the Losmandy GM-8 and G11 mounts) worked much better as the unbalancing amount was always the same ...

 

Rainer

 

Everything I’ve read suggested it’s a good ideal to have some bias to keep gears meshed together. Usually there isn’t a specific mention about with or without spring loaded mechanism. So I interpret that as a general principle. I’m sure I’m not the only one who has thought that. Life is for learning so you learn something new everyday!

 

The origination for needing the bias as you described it makes sense. I have a general understanding about the spring loaded worm so in theory that should take care of the gears staying meshed well. I’m not 100% sure there is NO backlash with MY mount or if it matters if there is a little, so I’ll continue testing until I’m sure backlash is not an issue.

 

I was aware that the CW was not as ineffective as the angle changes and the string method maintained a more consistent weight bias. Creative solution so congrats!

 

There is a lot of information out there and sorting out what is fact and what is something else gets confusing. 

 

Thanks for sharing.


Edited by HxPI, 13 June 2018 - 04:26 PM.


#25 Real14

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Posted 13 June 2018 - 04:45 PM

Hi,

 

I’m not 100% sure there is NO backlash with MY mount or if it matters if there is a little, so I’ll continue testing until I’m sure backlash is not an issue.

OK, there could be still some backlash when the mount has a spur gear.

 

In the case of iOptron with no spur gears inbetween then the really only possible available backlash is a non correct tensioned timing belt. When the belt is loose and you change direction you need to take out the belt slack and that takes some time until it is tensioned.

 

You can see a well tensioned belt compared to a loose tension belt in the following image.

 

IMG_3643_C1_loose1.jpg IMG_3644_C1_loose2.jpg

IMG_3642_C1_loosebelt_CN.jpg IMG_3659_C1_CN_correctbelt.jpg


Edited by Real14, 13 June 2018 - 04:47 PM.

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