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Counterweight on Ioptron CEM25EC

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#1 meegja

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Posted 07 July 2020 - 04:12 AM

Hello

 

I have the Ioptron CEM25EC for my Meade LX65 8" f/10 ACF OTA and it works really, really well. With my whole setup I am just above 50% of the max payload, so that's okay.

But the provided counterweight of 4.7 kg is not enough so added a 1.25 kg dumbbell weight (long live ducttape wink.gif ) and that was just enough.

But now with my new Zwo ASI294MC Pro it's really on the limit: the counterweight is really on the end of the bar with maybe a centimeter to spare.

I did find info here on NC about this already but still this question.

 

So, what is wisdom: do I get 2 x 1 kg or 1 x 2 kg extra? (and remove the ducttaped 1.25 kg ofcourse). And what is the best way to distribute the counterweights: the heaviest at the beginning of the bar and then balancing with the lightest one or the other way around?

 

Thanks in advance

Menno 


Edited by meegja, 07 July 2020 - 04:13 AM.


#2 gotak

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Posted 07 July 2020 - 07:30 AM

Best for any mount is the most mass closest to the axis. To reduce the moment arm. However, in your case i don't believe it makes much of a difference if you try your best to keep the two weights as close together as possible.
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#3 meegja

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Posted 07 July 2020 - 10:37 AM

Best for any mount is the most mass closest to the axis. To reduce the moment arm. However, in your case i don't believe it makes much of a difference if you try your best to keep the two weights as close together as possible.

Okay, thanks!



#4 OldManSky

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Posted 07 July 2020 - 12:30 PM

Yes, get a little more weight than you need, and keep the weights up close to the RA axis instead of out on the end of the CW shaft :)

 

It's too bad you're so far away, meegja.  I have two "leftover" CWs for a CEM25 just sitting here...I'd give them to you for free if you could do a local pickup!  Selling them is a pain because it costs so much to ship what is basically dead weight... :(


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#5 meegja

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Posted 08 July 2020 - 02:54 AM

Yes, get a little more weight than you need, and keep the weights up close to the RA axis instead of out on the end of the CW shaft smile.gif

 

It's too bad you're so far away, meegja.  I have two "leftover" CWs for a CEM25 just sitting here...I'd give them to you for free if you could do a local pickup!  Selling them is a pain because it costs so much to ship what is basically dead weight... frown.gif

Ah thanks :)
Btw, what is considered a "little bit more" in the case of counterweights?


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#6 OldManSky

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Posted 08 July 2020 - 05:57 AM

Ah thanks smile.gif
Btw, what is considered a "little bit more" in the case of counterweights?

2-5kg.  Or so. I was intentionally vague, 'cause it depends on your setup.



#7 meegja

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Posted 08 July 2020 - 06:11 AM

2-5kg.  Or so. I was intentionally vague, 'cause it depends on your setup.

Ahh, I thought you ment something like 500 grams :)
My setup is the mount with a max payload of 12.3 kg. My OTA plus everything attached is around 6.4 kg. And my current counterweight in total is 6.5 kg. But what you are saying is that in my case, 8 kg counterweight would do a "better" job because then it's a bit more to the RA-axis?

But also getting 2 different advises here then because Gotak reacted that in the case of this mount, it doesn't make much of a difference?



#8 OldManSky

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Posted 08 July 2020 - 07:35 AM

Ahh, I thought you ment something like 500 grams smile.gif
My setup is the mount with a max payload of 12.3 kg. My OTA plus everything attached is around 6.4 kg. And my current counterweight in total is 6.5 kg. But what you are saying is that in my case, 8 kg counterweight would do a "better" job because then it's a bit more to the RA-axis?

But also getting 2 different advises here then because Gotak reacted that in the case of this mount, it doesn't make much of a difference?

I had the mount for over a year, and imaged with it every clear night.  In my experience, it makes a difference.  The mount likes to be really well-balanced, and have a short moment arm -- which means the counterweights as far up the shaft as possible.  It performed much better in that configuration than when they were down near the end, or even in the middle.


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#9 meegja

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Posted 11 July 2020 - 02:31 PM

Okay, an update. Last night I tried both more weight close to the mount (7.5 kg) and less weight at the end of the barrel (5.2 kg). To achieve that, I removed my 7 x 50 finder scope that I only use whit GoTo aligning (nope, I don't plate solve wink.gif )

Less weight on the end of the barrel clearly wins. It all was way smoother then, tracking was also better. More weight close to the mount was more .... I don't know the English word .. "rougher"? The movement when slewing was not as fluent as with less weight at the end.




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