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Reflector Focusing Issue

Collimation Equipment Observing Reflector Visual
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#1 Calla1995

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Posted 01 December 2022 - 02:47 PM

Hi all,

 

I am starting an astronomy club up at the school I work at as they have a lovely unused large SkyWatcher telescope with HEQ5 mount and tripod.

 

I also have my own telescope and I understand quite a bit about telescopes, but I am having issues with the focus of distant objects on the supplied telescope at the school.

 

Through the eyepiece I can see high detail in things like tree branches etc but the telescope does not seem to resolve sky objects such as the Moon or Jupiter. They appear as a large bright circle with no detail even when the focuser is all the way out or in, using different eyepieces, ambient scope temperature achieved, mirrors collimated, mount and tripod balanced etc...

 

Can you offer any advice on what to do as it would be a shame to not be able to make use of this!

 

Many thanks,

Calla1995



#2 photoracer18

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Posted 01 December 2022 - 02:55 PM

Picture of scope please. Some kind of Newtonian reflector?



#3 vtornado

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Posted 01 December 2022 - 03:12 PM

It sounds like a focus issue.  

Watch Jupiter's disk as you move the focuser.  If it is getting larger you are going the wrong way.  If it is getting smaller you are going the right way.

 

If as it approaches the smallest disk and you have moved the focuser all the way out, try

pulling the eyepiece slowly out of the draw tube and see if you can obtain focus.

If you can, note the position, and purchase an extension tube.

 

If you run out of focus going in, that is more trouble.

 

VT


Edited by vtornado, 01 December 2022 - 05:19 PM.

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#4 kathyastro

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Posted 01 December 2022 - 03:37 PM

If you can focus nearby objects like trees, but not distant objects like the Moon or stars, even with the focuser racked all the way in, then the eyepiece is too far out.

 

Maybe the focuser was replaced with one that was longer than the original.  Maybe the mirror was replaced with one that had a shorter focal length than the original.  Maybe the eyepiece in question is just not compatible with that scope's focuser.


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#5 Bean614

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Posted 01 December 2022 - 04:18 PM

There might be an "extension" attached to the focuser, as these are often supplied by the manufacturer to enable different eyepieces to come to focus.  If so, remove the extension. 


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#6 SteveG

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Posted 02 December 2022 - 05:24 PM

Hi all,

 

I am starting an astronomy club up at the school I work at as they have a lovely unused large SkyWatcher telescope with HEQ5 mount and tripod.

 

I also have my own telescope and I understand quite a bit about telescopes, but I am having issues with the focus of distant objects on the supplied telescope at the school.

 

Through the eyepiece I can see high detail in things like tree branches etc but the telescope does not seem to resolve sky objects such as the Moon or Jupiter. They appear as a large bright circle with no detail even when the focuser is all the way out or in, using different eyepieces, ambient scope temperature achieved, mirrors collimated, mount and tripod balanced etc...

 

Can you offer any advice on what to do as it would be a shame to not be able to make use of this!

 

Many thanks,

Calla1995

Can you describe the telescope? Skywatcher (what).



#7 Bill Weir

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Posted 03 December 2022 - 01:28 AM

It’s a Skywatcher and they have those unique focusers. My guess is that you have the adapter for 1.25” eyepieces inserted into the adapter for 2” eyepieces. You need to take the 2” one out before inserting the 1.25” one. It’s a weird arrangement but it is what it is. I’ve seen this problem before. 

 

Bill



#8 Calla1995

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Posted 06 December 2022 - 02:16 PM

Hi all,

 

I removed the extension tube, and low and behold, it worked! What a strange thing to have on that makes focusing initially difficult!

 

Many thanks for your advice!

 

Calla1995




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