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Addressing camera mount clearance issues with a diagonal

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#1 sudeepban

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Posted 16 November 2019 - 10:42 PM

I've been enjoying using my 8SE with the ZWO 294MC Pro and Celestron f/6.3 reducer for EAA, but I'm looking to address the mount clearance concerns that currently limit me to observing targets 60 degrees above the horizon or lower.

Does anyone have thoughts on using a diagonal to avoid the clearance issues? The helpful folks at High Point Scientific suggested adding something like these between the scope and reducer:

https://www.highpoin...elescopes-93527

https://www.highpoin...-adapter-la1060

Would love to hear if others have had success or any issues doing similar things.

#2 Barkingsteve

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Posted 17 November 2019 - 05:30 AM

Have you considered a wedge ? i was considering one for my evolution mount to solve the clearance issues, then i saw the cem40 mount and decided i need to save :) 



#3 nic35

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Posted 17 November 2019 - 08:20 AM

S:

 

I dont have an SE mount, but my Evolution runs into the same problem.  I use the Celestron diagonal, but also have a 2" adapter similar to this one https://www.adorama....YRoCgPsQAvD_BwE

 

The lumicon adapter confuses me - how does one secure your diagonal in that ?

 

I also picked up a right angle USB 3 cable from Ebay to minimize the space needed for the USB cable to clear the mount.

 

Even with these I have to move the scope far forward in the dovetail holder, which imbalances the scope.  Not a major issue with the Evolution mount, not sure about the SE.

 

john



#4 GoFish

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Posted 17 November 2019 - 08:44 AM

How will you set the recommended 105mm spacing from reducer to sensor? I’ve always been puzzled about measuring optical path length when a diagonal is involved. 



#5 sudeepban

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Posted 17 November 2019 - 08:55 AM

How will you set the recommended 105mm spacing from reducer to sensor? I’ve always been puzzled about measuring optical path length when a diagonal is involved.

I think the idea is to use the diagonal between the scope and the reducer so that the spacing between the reducer and camera is completely unaltered.

#6 sudeepban

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Posted 17 November 2019 - 09:05 AM

Have you considered a wedge ? i was considering one for my evolution mount to solve the clearance issues, then i saw the cem40 mount and decided i need to save :)

Hmm, wasn't thinking of making the leap to polar aligning yet. I feel like I've also heard mixed reviews on using a wedge with an alt-az mount. I'm thinking I'm looking to incrementally improve my current setup for now and could invest in an overall better, equatorial mount much further down the line.

#7 sudeepban

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Posted 17 November 2019 - 09:16 AM

S:

I dont have an SE mount, but my Evolution runs into the same problem. I use the Celestron diagonal, but also have a 2" adapter similar to this one https://www.adorama....YRoCgPsQAvD_BwE

The lumicon adapter confuses me - how does one secure your diagonal in that ?

I also picked up a right angle USB 3 cable from Ebay to minimize the space needed for the USB cable to clear the mount.

Even with these I have to move the scope far forward in the dovetail holder, which imbalances the scope. Not a major issue with the Evolution mount, not sure about the SE.

john

So I might be mistaken, but wouldn't the adapter just fit right in to the angled up side of the diagonal and be locked in with the diagonal screws? Then it would expose the SCT receptacle, which the Celestron f/6.3 reducer fits right into.

With proper balance, how high above the horizon can you target? Do you get full clearance with an imbalanced setup? I'm also not quite clear on the consequences of not having things balanced, but that is something I was a little worried about with adding more weight on the back of the scope.

Edited by sudeepban, 17 November 2019 - 09:19 AM.


#8 Clouzot

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Posted 18 November 2019 - 09:45 AM

With proper balance, how high above the horizon can you target? Do you get full clearance with an imbalanced setup? I'm also not quite clear on the consequences of not having things balanced, but that is something I was a little worried about with adding more weight on the back of the scope.

With my stock Evo 9.25, x0.63 reducer, 1"25 diagonal and some spacers before the camera (183 uncooled), I can target 65° above the horizon (not a show-stopper though, as alt-az perform poorly towards the zenith anyway).

 

By allowing the OTA to be a bit nose-heavy, you can reach 70°-75°-ish, but straining the Evo mount is probably not a good idea so I don't try to reach full clearance. And that prevents the use of a competent dew-shield then (too heavy).

 

With the Hyperstar + counterweight, I can definitely reach the zenith, but of course the camera is sitting on the corrector plate then.



#9 donstim

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Posted 18 November 2019 - 01:36 PM

WIth my EVO 8, and an imaging train consisting of a Celestron 0.63x reducer, 1.25-inch visual back, Baader T-2 1.25-inch star diagonal with the eyepiece holder removed so that my ZWO ASI294MC Pro camera with 11mm extender ring and 16.5 mm extension can be directly screwed onto the star diagonal, I can reach the zenith with the telescope OTA about as far forward as it can go on the dovetail.  I use a dew shield plus Reflectix, and yes, the scope is definitely unbalanced in this configuration.  But, I have not noticed any issues and the scope tracks great for EAA use (<30 second exposures) up near the zenith.  (In fact, I have been pleasantly surprised with how well it tracks up there.)

 

For objects less than 62 degrees in altitude, I don't need to use the star diagonal, but I'm plenty happy with the images I get when using the diagonal.

 

I've been thinking of installing some balance weights in some manner at the rear of the scope to provide a more balanced scope, but I haven't seen anything yet that I'd be happy with.  This thread echoes my experience with an unbalanced EVO 8 (that it's not an issue):  https://www.cloudyni...-for-evo-mount/

 

This might not hold true for the less beefy SE mount.


Edited by donstim, 18 November 2019 - 03:07 PM.



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