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CEM60 Balance issues

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#1 najarfermin

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Posted 14 July 2019 - 10:51 PM

Hello everyone,
I'm the owner of a CEM60, I'm using it mostly with a Explore Scientific 127 mm Triplet Apo Carbon Fiber.
https://explorescien...in-carbon-fiber
 
I have to say that this mount is very hard to balance. I know balance in astrophotography is a well known difficult subject
but I think this mount is harder to balance compared to others.
 
I used the very  same telescope/accesories with a Celestron AVX I already own and I felt that it was way less harder to balance with the same setup.
I had to do a extensive research how to achieve a good balance with the CEM60; and what I found is that several people had to use extra
accessories or made-up components to achieve that balance.
 
I already looked at this
https://www.youtube....h?v=X8w77MrpB3o
https://www.cloudyni...-cem60-wvideos/
 
I applied some of the same solutions and I put some fenderwashers like this:

 

balance5.jpg
 
But even with that, sometimes work, sometimes doesn't. And if I did some tiny mistake like not put the focuser in the right place or forgot a single tiny cable, the mount

get unbalanced awfully and I have to start over.

 

Then I decided to give a try with another scope  I have on the CEM60, the Explore Scientific 80 mm Carbon Fiber. Its really so much smaller than the other.

https://explorescien...tic-refractor-1

 

- With the Celestron AVX, bum !!!! 5 minutes, it's balanced. No pain no suffering at all, only happiness and I got enough time to do a party and invite everyone.

- With the CEM60 , I gave it a try, can't achieved yet. I'm still hitting my head on the wall....

 
Then I asked IOptron for support and they came back with this:
 

cem60_cw-2.jpg
 
 
Another extra accessory .... and I'm not 100% satisfied of the IOptron's support....
 
Bottomline: my questions for you guys are the following:
 
a) Do you know some method or accesories to make easier the balance process of this specific mount ? 

 

b) It is worth to continue to invest time and money with this mount ? As I previously mentioned, doing a research I found that many people have the same troubles balancing this

specific mount, and I already spent  several nights dealing with this issues, loosing night time and almost not achieving a good balance. May I shall sell it and buy a better mount,

I don't know... after some months of having it I'm running off of patience...

 

c) Maybe I'm doing something wrong ?

I have to clarify: I'm not looking the holy grail perfect balance with this mount, only a decent good balance.

 

Thank you for your help  !

 
Regards

Attached Thumbnails

  • balance5.jpg
  • cem60_cw-2.jpg


#2 scadvice

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Posted 14 July 2019 - 11:27 PM

I read your post twice and if I'm understanding correctly you maybe overthinking this whole balance thing. I suggest getting rid of the added weights and try balancing in the Dec until a very light finger push, up or down, will hold it... east and west after doing the same in the RA. Then slew the axis as far as you can in both axis without hitting anything. If the slewing is smooth and the motors do not squeal your mount is ready to go. 

 

I have owned both the GEM25P and the CEM60. I had one scope, one scope with a finder, one with a larger guider one finder on them.  I now have  a larger scope (130 triplet) and a 80mm guider plus a finder on my CEM60..

 

What I've found after hours and hours of testing with and without added weights that the iOptron center balanced mounts do not react like the standard GEM.  Mine... almost always... has one side very slightly different in the east as it is in the west... yet it never has effected guiding or performance. I use some small side weights but they are only there to offset the finder scope that is mounted on the opposite side. 

Attached Thumbnails

  • 130t2.jpg

Edited by scadvice, 15 July 2019 - 11:23 AM.

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#3 Gipht

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Posted 14 July 2019 - 11:32 PM

I have a CEM-60 and use it with multiple telescopes  ranging from a 70mm f/6 to a 10" f/4 reflector.  I do often have to change the balance of the counterweight when I cross the meridian.  Otherwise the balance seems to work fine.  I have just the counterweight on the shaft and no additional counterweights.  I do adjust the position of the dovetail for Dec balance.

 

Perhaps giving us the problem your trying to solve will help, for example: does the mount stall during slewing?


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#4 oshimitsu

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Posted 14 July 2019 - 11:45 PM

I think what Ioptron was talking about is that you have to spin the telescope around in it's tube to achieve balance from that axis as well. I have to have my camera facing down at an odd angle to balance my CGX, the AVX's axis are a lot more stiff compared to the CM60 so it isn't as noticeable.



#5 niccoc1603

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Posted 15 July 2019 - 12:29 AM

From my experience with CEM25P and now CEM40 a little imbalance does not affect performance at all.

Achieving perfect balance on CEM is very hard since when the gear is unlocked there is no friction at all

With my new CEM40 I went from being always west-heavy, then I adjusted the counterweight shaft (rotate a bit east) and i got perfect balance, then I added some weights to make it east-heavy because “it is recommended”
Result: exactly same guiding performance in all the three cases

So unless you have a strong imbalance I would not be ossessive about it

Edited by niccoc1603, 15 July 2019 - 12:37 AM.


#6 RaulTheRat

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Posted 15 July 2019 - 01:41 AM

I'd be interested to hear if anyone is using the threaded holes on the counterweights for off-axis balance as I don't have my CEM60 yet but I don't understand how they are supposed to work - given that the counterweight bar doesn't rotate with the declination axis, any weight you put sticking out of the sides of a normal counterweight won't follow the scopes rotation in declination, so I don't understand how those off-axis counterweight holes can be useful - if anyone is using them and can explain I'd be grateful.

#7 strelnikoff

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Posted 15 July 2019 - 02:39 AM

This has just taken me back from the idea of purchasing CEM60. Now I have to convince myself again it’s an improvement to my current AVX. Have you noticed any improvements - aside from these issues and tinkering with balance?



#8 Der_Pit

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Posted 15 July 2019 - 06:35 AM

Well, of course if you use a caliper instead of a plastic school ruler you measure stuff you couldn't see before.  That doesn't mean it wasn't there before.  The balance of your other mount is not easier or better - on the contrary.  Its friction prevents you from balancing better than 'approximately OK'.

The CEM just shows you what imbalance still was left before wink.gif

 

Now for the extra threaded holes in the CW - I don't use them, I try to balance the OTA itself by adding weights (only) there.  It's a bit more work the first time, but once the left-right balance is done, doing the normal balance after removing and re-adding the OTA is a matter of a minute.  And I don't have to watch and/or note the orientation of the CW when fixing/shifting it....



#9 najarfermin

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Posted 15 July 2019 - 06:44 AM

This has just taken me back from the idea of purchasing CEM60. Now I have to convince myself again it’s an improvement to my current AVX. Have you noticed any improvements - aside from these issues and tinkering with balance?

The mount itself, besides the balance problem, is a box of features: integrated GPS, cable management, integrated polar scope ( that I never used because I have the pole master ), double saddle for vixen/ losmandy, etc.
 


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#10 najarfermin

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Posted 15 July 2019 - 07:00 AM

I think what Ioptron was talking about is that you have to spin the telescope around in it's tube to achieve balance from that axis as well. I have to have my camera facing down at an odd angle to balance my CGX, the AVX's axis are a lot more stiff compared to the CM60 so it isn't as noticeable.

I already try to spin the tube and other several things, the only thing to seems to work (and not every time) is the fender washers that add a off-axis counterweight



#11 najarfermin

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Posted 15 July 2019 - 07:10 AM

Thanks for your replies guys !! Mostly of my problems come with the DEC axis. I'm already aware that unbalance comes with some accessories, but balance the same setup in AVX its no problem at all.

 

I did a video to show the problem. And take note of this: if it wasn't for the c-clamp & fender washers in the RAC axis, will be unbalanced too.

This is not only a problem with that setup.

https://www.youtube....h?v=ula5ShgC158



#12 spokeshave

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Posted 15 July 2019 - 07:16 AM

The AVX is notorious for friction on both axes even when unlocked. So, imbalance can be hidden by the friction since the mount won't move even if there is some imbalance. The CEM60, on the other hand, has very little friction when unlocked, so any imbalance at all will be evident. So, it is very likely that the same imbalance existed with the AVX - you just couldn't see it. That is what iOptron support is trying to tell you.

 

Tim


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#13 najarfermin

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Posted 15 July 2019 - 08:09 AM

Good point  spokeshave



#14 Tom K

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Posted 16 July 2019 - 12:53 PM

The AVX is notorious for friction on both axes even when unlocked. So, imbalance can be hidden by the friction since the mount won't move even if there is some imbalance. The CEM60, on the other hand, has very little friction when unlocked, so any imbalance at all will be evident. So, it is very likely that the same imbalance existed with the AVX - you just couldn't see it. That is what iOptron support is trying to tell you.

Tim


+1 on this. I have owned both and AVX and a CEM60 and the AVX can't sense imbalance until it is really bad. If you are very close with the CEM60 you are probably good enough.


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#15 denny-o

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Posted 27 July 2019 - 03:03 PM

OP - any new thoughts?



#16 BobW55

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Posted 06 August 2019 - 09:56 PM

I have the CEM60 and chased the "PERFECT" balance at first.

I finally figured if I can unlock both axis and push it around, or stop it with my pinky finger I got it.

I too have noticed a shift when doing a meridian flip, but not enough to make me want to balance it again.

I am using a ES 102mm, with a finder scope mounted on the handle, RA was easy to obtain by shifting the OTA slightly in the rings, and the main counter weight.


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