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Payload Capacity limit

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#1 Robbie1369

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Posted 18 September 2021 - 09:21 AM

Hi I have a 9.25inch Celestron on an AVX mount. I always worry I do not understand my limit to payload capacity. The AVX mount has a 30lb limit and my OTA is 20lb. I believe this leaves me 10lb left. Does the OTA include the finderscope? If not what is weight of the supplied finderscope. I wish to get an cooled mono ZWO camera.. then maybe filter wheel.. am I still in the safe zone?

#2 Keith Rivich

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Posted 18 September 2021 - 09:45 AM

Set everything the mount has to carry on a scale, minus the counter weights. See what ya got. If you come in around 20lb you are good to go. More then that I would consider a higher capacity mount. 



#3 Nick Dangerr

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Posted 18 September 2021 - 10:05 AM

My understanding of the rule of thumb for AP mounts is that the payload limit should be twice the total weight of the actual payload. So you may have some issues with stability with AP.



#4 barbarosa

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Posted 18 September 2021 - 10:06 AM

Celestron defines payload as, "Celestron's payload capacity is the weight the mount and dovetail clamp can hold when adding on the optical tube and the accessories you wish to use with your scope (Finderscope, StarSense, Camera, etc). Celestron's payload capacity does not include the weight of the counterweights."

 

Optical tube assembly as used is generally defined as being the telescope tube (or truss) and optics. There is  some ambiguity in the use of the term. Celestron excludes the weight of the dovetail bar from the OTA weight (or has an error in the product specs) while Meade gives an assembled product weight that appears to include the bar or rings and may include the finder scope and diagonal.

 

Your best bet is weigh it yourself.

 

Payload capacity is not an industry standard, with some mounts you can use all of the specified payload without a performance loss. Some say that some mounts can be overloaded without harm, Nexstar SE and CPC owners have been known to exceed the factory payload spec. iOptron CEMs can be operated at full payload and perform well.

 

There is a rule of thumb that for imaging you should use only one half of the rated payload. This is not applicable to all mounts, though it may have been true of older designs and less expensive mounts today. AVX imagers may have better and specific advice.


Edited by barbarosa, 18 September 2021 - 10:09 AM.

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#5 RTLR 12

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Posted 19 September 2021 - 05:42 PM

My Edge 9.25 weighs right at 30lbs completely dressed with VB, diag, Ep, and finder scope. I only use it for visual viewing and it is right at the limit for practical purposes. When doing any AP work the general rule of thumb is
no more weight than 50% of mount capacity. If you are serious about doing AP work you will need a higher capacity mount.

Just my opinion,

Stan

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Edited by RTLR 12, 19 September 2021 - 05:45 PM.

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#6 Robbie1369

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Posted 19 September 2021 - 06:43 PM

What I do not understand is your OTA weight is 21Kgs leaving you 9kgs spare. The VB Diag and basic view finder must be a few grams and a camera may weigh 250gs ish I feel I am missing some logic somewhere. If we say all things weigh all in a 1kg.. then that leaves a safe 4Kgs spare for reliable AP ( 50% spare capacity) why are you already up to the full limit using up the 9kgs.
My understanding is you do not add the counterweights?

Edited by Robbie1369, 19 September 2021 - 06:56 PM.


#7 RTLR 12

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Posted 20 September 2021 - 02:19 PM

I'm sorry, but I don't quite understand your math (4kg = 50% of 30lb) and why you switched from pounds to killograms? You are correct about NOT adding the counterweights.

 

I forgot to mention that I had encluded my dew sheild with the total weight of the OTA etc and that I was just guessing off the top of my head. I can give you a component breakdown by weight;

 

I weighed all of these items on a postal scale;

 

Celestron Edge 9.25 OTA..................21lbs.

Rotating Starzonia VB........................13oz.

Celestron 9X50 finder & mount..........1lb.12ozs.

Astro-Physics Maxbright diag.............1lb 8oz.

WO red dot finder................................7oz.

Dew shield...........................................2lbs 10oz.

 

The total weight that I come up with is 28lbs. 2oz.

 

Celestron list the mount capacity at 30lbs.

 

Half of 30 pounds is 15 pounds. By my calculations that means that I am 13lbs 2oz over the rule of thumb 50% weight limit for AP. At this weight, I found the mount to be right on the edge for stability for visual veiwing. 

 

This is just what my set up looks like and how I feel about it. You may have different components and weights. I feel that an Edge 9.25 is too much wieght for an AVX mount if want favorable results doing AP.

 

Opinions vary,

 

Stan


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#8 Robbie1369

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Posted 20 September 2021 - 06:05 PM

Thanks for making things clearer to me Stan

#9 Robbie1369

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Posted 21 September 2021 - 06:26 PM

RTL12 That was a good post for me. It doesn't help when I jump back and forth from the metric to emperial systems. Listing the items as you did makes it clearer for me, thanks

#10 RTLR 12

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Posted 21 September 2021 - 09:51 PM

Robbie1369,

I’m glad that my posting helped. That’s what it’s all about. I hope you get to where you want to be with your equipment. It can certainly be overwhelming and very confusing.

Good luck, and keep asking questions...

Stan


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