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AR152 Mod for Binoviewing

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#26 Jeff B

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Posted 21 July 2020 - 07:33 PM

I’ll be documenting the whole process right here. Pictures and all. 

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#27 StarAlert

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Posted 22 July 2020 - 11:21 AM

I got a call from ES today. Kent measured the backfocus on the AR152 at 165mm. Makes sense because the 2” draw tube is about 6.75” long. Racked all the way in, the front of the focuser draw tube would be just over 13” (6.5” back focus + 6.75” draw tube total length) in front of the scope’s focal plane. At that point, the light cone is 2” wide. 



#28 StarAlert

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Posted 31 July 2020 - 10:26 PM

I had to send my flange adapter to Wayne at Starlight so he could machine a new one to fit the FT focuser to the OTA. Looks like my FT upgrade is going to be a bit delayed. 



#29 Eddgie

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Posted 02 August 2020 - 04:14 PM

I have a t2 prism diagonal. In total, I need a minimum of 220mm of backfocus. I think the AR152 has 180mm. 

That seems rather a lot.  What binoviewer are you using?

For example, if you are using a Maxbright II, the light path of the BV is 110mm and if directly attached to the top of the T2 prism, that is only 40mm more, for a total of 160mm.  

 

Even the Televue, which has about 130mm of light path, would still only need 180mm of back focus.

 

To answer your question though, if you go to the larger tube you should be OK.  Make sure that there is no baffle in the tube that would restrict the forward movement of the focuser.

 

If you have 180mm though, I would think you could reach focus with most many binoviewers in a T2 direct connection to the T2 prism diagonal. 

 

Be aware though that you might now need an extension to get regular eyepieces to reach focus. 


Edited by Eddgie, 02 August 2020 - 04:15 PM.


#30 StarAlert

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Posted 02 August 2020 - 05:13 PM

That seems rather a lot.  What binoviewer are you using?

For example, if you are using a Maxbright II, the light path of the BV is 110mm and if directly attached to the top of the T2 prism, that is only 40mm more, for a total of 160mm.  

 

Even the Televue, which has about 130mm of light path, would still only need 180mm of back focus.

 

To answer your question though, if you go to the larger tube you should be OK.  Make sure that there is no baffle in the tube that would restrict the forward movement of the focuser.

 

If you have 180mm though, I would think you could reach focus with most many binoviewers in a T2 direct connection to the T2 prism diagonal. 

 

Be aware though that you might now need an extension to get regular eyepieces to reach focus. 

In my post #13 above I identify how I got the 220mm. Tak has 55mm of adapters on the end if the focuser tube that is included in their 223mm of backfocus (I think). So, if that stuff isn’t there, 180mm should be enough. 




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