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What adapter/tube do I need to use a 2" 2X barlow on my Astro-Tech AT66ED?

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#1 Bassius

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Posted 24 May 2024 - 02:44 AM

Hello Everyone,

 

In december I bought a 2nd hand Astro-Tech AT66ED to get into astrophotography. Because of reasons I have only been able to start messing around with it properly since last week. 

 

I took some decent images of the moon, but I would be better of with more magnification because right now it needs a lot of cropping (and thus loss of detail). Considering I have 2X barlow for/from my 8" dobson, I tried to use it on this refractor but it doesn't fit. Basically the problem is that the barlow and the telescope tube have the same diameter. I'm thinking I probably need some sort of adapter/extension tube that I can screw on the thread (on the telescope) and then shove the barlow in on the other end. But what exactly am I looking for? What is it called? 

 

I don't want to mess around with extension tubes too much, because (correct me if i'm wrong) it also messes up my focus travel... 

 

Thanks in advance!



#2 Tapio

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Posted 24 May 2024 - 06:49 AM

Normal barlow should be 1.25" size, same as eyepieces. So it should go where you put eyepiece, like a diagonal.



#3 Cliff Hipsher

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Posted 24 May 2024 - 01:33 PM

Post some pictures so we can see what we are dealing with...



#4 Cometeer

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Posted 24 May 2024 - 03:20 PM

Normal barlow should be 1.25" size, same as eyepieces. So it should go where you put eyepiece, like a diagonal.

A normal barlow can be 2” too.


The AT66ED comes with a 1.25” visual back on it. Your best bet is to have a custom adapter made at Precise Parts to from go the drawtube threads to a 2” visual back. There’s still the risk of it not reaching focus since the barlow is too wide to go inside the focuser. This would also cost you $150 to have made. Depending on your sensor size, I’d consider switching to a 1.25” barlow or selling your scope and upgrading to an AT60ED. It has a superior 2” rack and pinion focuser and uses better glass (and would likely cost the same as selling your current scope and putting the extra $150 towards the new one).

Edited by Cometeer, 24 May 2024 - 03:20 PM.


#5 SporadicGazer

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Posted 24 May 2024 - 03:40 PM

(For everyone, like me, who didn't know a AT66ED existed and assumed the title was a typo:)

 

https://www.cloudyni...refractor-r1418

 

It says it came with a 1-1/4" visual back, but was also threaded to use SCT 2" diagonals.

 

I wonder from the description that it is used for photography if maybe it came without the visual back.  This:

 

https://agenaastro.c...ined.html#small

 

says the SCT threads are 2"-24.  (2" nominal diameter and 24 tpi (threads per inch))


Edited by SporadicGazer, 24 May 2024 - 03:41 PM.


#6 eblanken

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Posted 27 May 2024 - 04:06 AM

Hi All,

 

Just an idea, might a 2 inch visual back for a Meade or Celestron SCT help in this instance ?

 

Link: https://www.highpoin...AiABEgLtxvD_BwE

 

Ed (aka eblanken)

 

P.S. Also, is a full 2x Barlow needed, or could a cell be applied to the filter threads of the camera to get something like 1.5x ?


Edited by eblanken, 27 May 2024 - 04:13 AM.



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