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102ED Refractor on top of SCT Evolution 8 EdgeHD with CPC tripot

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#1 Matthew Star

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Posted 23 October 2021 - 08:06 AM

I already have a heavier variant Celestron Evolution GoTo mount with the heavy CPC tripot, StarSense and Focus Motor, but still no telescope at all.

 

I am in between of buying a 9.25 EdgeHD or a 8 EdgeHD.

The 9.25 fills the cap of 8" and 11" nicely and they seem to come out more perfect compared to the others even as a non EHD.

 

What can drive me to the 8 EHD is maybe the lower weight that leaves room for a bigger finder scope for the mount as in,... a 4" refractor

Is it possible to attache a AT102ED ( or TS Optics version, sinse AT is not in the EU) on a 8 EdgeHD with rings or tights, runing on the Nexstar Evolution?

 

I wanted an iOptron Pro mount for that, but the StarSense and Focus Motor drove me to Celestron.

So now, I have to bring 2 mounts with scopes, unless I can combine them afterall.

 

 

 


Edited by Matthew Star, 23 October 2021 - 08:12 AM.


#2 junomike

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Posted 23 October 2021 - 08:16 AM

Firstly, for visual you may be happy enough with a standard C925.  I did notice a difference in the 8" EdgeHD (over the standard version), but those differences for visual are a lot less in the C925/C925 EdgeHD.

 

Secondly, you should be able to mount a small Refractor with an 8" SCT on the Evo, however it's more a lesson in frustration.  Using the rings as you suggest will also throw off the COG and thus make the Mount more prone to tipping. 

A Side-by-side set up would be easier and safer IME.

 

My advice would be to use the Mount with one OTA or the other.


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#3 Matthew Star

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Posted 24 October 2021 - 05:48 AM

If I turn the second guiderscope-Refractor towards/over the Nexstar GoTo scope Grip part, would that balance the whole set better?

I amagine that for the GoTo grip system it will be less heavy to work.



#4 Matthew Star

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Posted 26 October 2021 - 02:47 AM

With th iOptron it is a matter of balance and can than easily be pushed over the max limit. Will this somehow work with the Nexstar Evolution?

Anybody who done this, failed or succeed?


Edited by Matthew Star, 26 October 2021 - 02:50 AM.


#5 jason_milani

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Posted 27 October 2021 - 08:09 PM

There is no way I'd use an Evolution mount with  a C8 AND a 102mm refractor piggybacked.  I don't care what tripod you use.  There would be major vibration issues.  Now, a CPC 8  and the refractor may work.


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#6 Sacred Heart

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Posted 28 October 2021 - 07:32 AM

My advice listen to what jason_milani and  junomike  have to say.    You want to be able to enjoy looking or imaging, not adjusting this or that, rebalancing,  why is this not tracking right.   These are real problems you might be looking at if you put these two scopes together on this mount.          If you already have this mount,  get the scope it was designed for and no more.

 

     Now this is my opinion strictly,  this mount should be used primarily as a visual and not an imaging device.  You can image, but short exposures,  field rotation - alt az mount.   Also pay attention to your weight limits of the mount.  Me, no matter who makes it, I  stay at less than 80% of the mounts payload capacity.  I use the 20% that is left over for wind and other variables.    If you get the Schmidt,  get or make a dew shield.      Joe



#7 gnowellsct

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Posted 28 October 2021 - 08:05 AM

Having a refractor on top of your SCT is a fantastic way of observing and I've been doing it for 20 years.

I would not do it on the Celestron mounts I have seen. With a c8 or 925 LosMandy g11 is the ticket and what I have been using along with an AP 900 qmd.

I prefer the c8. I had a 925 and it's great. But I have settled into a very good relationship with the c8 and it's a performer. Combined with a 92 mm Apo it's a wonderful way to play in the sky. Found a 925 for a couple of years and one of my friends has a 925 which is top notch. But it hasn't motivated me to get my own 925. The c8 seems to be a keeper.

When I want more aperture I pull out the c14 and put it on the astrophysics mount and put the same 92 mm refractor on board.

There are significant technical issues in mounting a refractor on top of an SCT. It is extremely difficult and I would say almost impossible to do right if your goal is after photography. But I guess it can be done. The issue is flexure.

For visual purposes you have a problem it just won't ruin your photographs. You can go with a rigid ring system. If you do that the scope May never be in perfect alignment with the optical tube so you're going to have to accept that you will have to use the paddle with first one telescope and then the other in order to center the objects because it may not be centered in both at the same time.

Or you can get hardware that lets you rapidly adjust the second telescope to being alignment with the first so that every time you change position it only takes a second to get lined up.

I tried mounting side by side as many people suggest and it seems to work for them. My situation requires me to put everything into the car and drive out to the observing site and in the usual case I don't have anyone to help me with The balancing act that side by side requires. Even with the help of a friend that can get pretty hairy you've got a $5,000 c14 on one side and a three and a half thousand dollar APO on the other and the c14 weighs 40 lb and the APO weighs about 10 and I was struggling with this and then decided I just couldn't hack it. There were too many possibilities for things to go wrong.

If you go with top mounting you might consider a 92 mm instead of a 102 mm. The 92 mm will give you all those fantastic views and you won't be wishing you had a 102 mm because you've got the bigger scope right underneath. The 92 mm reduces the stress on the system. I'm talking mechanical stress.

I have tried an 81 mm and that works. The taking all the factors of performance and mounting issues I ended up moving from 102 to 81 and then from 81 to 92. 92 mm just seems to be where things work best.

Edited by gnowellsct, 28 October 2021 - 08:08 AM.


#8 carolinaskies

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Posted 28 October 2021 - 08:59 AM

The Evolution mount can handle up to the 9.25.  However to mount a refractor you'll need a Losmandy mounting plate for the refractor and rings. The total weight by the time you get all accessories in place will be enough to really stress the declination motor/drive system and single arm.   Rather than the 8" combo, consider a hybrid 6"/102mm combo on a saddleplate.  The total weight should be close to the 9.25 and you can balance the saddleplate mounting point better than offset a 102 on an 8". 

 



#9 gnowellsct

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Posted 28 October 2021 - 10:58 PM

C8+AP 92mm+G11+Berlebach tripod

 

c8 with stowaway.jpg


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#10 Matthew Star

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Posted 01 November 2021 - 01:24 AM

Rather than the 8" combo, consider a hybrid 6"/102mm combo on a saddleplate.  The total weight should be close to the 9.25 and you can balance the saddleplate mounting point better than offset a 102 on an 8". 

 

 

What kind of plate do you mean and where to place it?

I kinda gave up on this, but now I'm curious.

My 9.25 Edge HD is not in yet, so I still can change it tfor a 8 Edge HD.




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