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#1 aorion314

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Posted 11 April 2021 - 11:34 PM

aorion314 here, there is an ES ED127 being offered for sale my question to all is ?? what effect does a spacer have on this telescope which needs to a require a spacer, per the seller helps to achieve focus. MY understanding of refractors is that there is focal point which allows one to see a coherent image, ??? is this a failure of the scopes design or some esoteric mechanism that I am unaware of, or what ? Any optical input from any CN'er would be appreciated, respectfully submitted.  PS  Dear CSA/Montana (moderator), since you often read and make changes/moves to my posts please be so kind as kind as to move this post/topic to where you think is a better match than equipment forum.



#2 SteveG

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Posted 11 April 2021 - 11:46 PM

aorion314 here, there is an ES ED127 being offered for sale my question to all is ?? what effect does a spacer have on this telescope which needs to a require a spacer, per the seller helps to achieve focus. MY understanding of refractors is that there is focal point which allows one to see a coherent image, ??? is this a failure of the scopes design or some esoteric mechanism that I am unaware of, or what ? Any optical input from any CN'er would be appreciated, respectfully submitted.  PS  Dear CSA/Montana (moderator), since you often read and make changes/moves to my posts please be so kind as kind as to move this post/topic to where you think is a better match than equipment forum.

 

Modern refractors are designed for visual use and imaging. Due to the imaging camera’s back-focus requirements, many refractors are made with shorter tubes to allow for more inward focus, thus sometimes requiring a focus tube extender to allow eyepieces to come to focus. My preference is to have a larger focuser that has more travel, not requiring the extension tube for imaging and visual.

 

That scope needs a substantial mount. What do you have in mind for it?



#3 vio

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Posted 12 April 2021 - 07:45 AM

The telescope is just one part of the imaging path, other devices also play a role in whether you can achieve the focus or not. You can use a 1.25” or 2” diagonal, different eyepieces, imaging with different cameras, maybe an on/off axis guider, possibly filters on a filter wheel. All these take space, the manufacturer may not know how you use the scope. The opposite, while convenient, may prescribe which accessories can be used.


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#4 airbleeder

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Posted 12 April 2021 - 08:30 AM

    The opposite of what?



#5 coopman

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Posted 12 April 2021 - 08:44 AM

The "spacer" is just an extension tube, a common accessory.


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#6 Jeff Lee

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Posted 12 April 2021 - 08:50 AM

ES ships two extension tubes with thier ES scopes. You use one for visual and two for imaging.


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#7 Jon Isaacs

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Posted 12 April 2021 - 09:28 AM

ES ships two extension tubes with thier ES scopes. You use one for visual and two for imaging.

 

It can also facilitate the use of binoviewers.

 

Jon


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