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Getting an ETX70 to focus with a .5 focal reducer

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#1 tomwall

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Posted 06 December 2018 - 12:40 PM

I'm using an ASI224 camera on my ETX70. I want to use my .5 focal reducer to image at f2.5, rather than f5. It won't come to focus through the standard diagonal. So, I tried the rear photo port. I still couldn't get it to focus. Any advice? Thanks!

 

Tom,

Tucson



#2 sg6

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Posted 06 December 2018 - 12:59 PM

There is not a lot to play with on an ETX-70, and I simply guess that the lens cannot be drawn/wound back sufficently for the reduced image to fall far enough out so it coincides with the sensor.


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#3 denny-o

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Posted 06 December 2018 - 02:36 PM

Yup. Gonna need a spacer to reach prime focus (forget about using the diagonal) I'm guessing something in the low 20's mm range of spacer depending on how far back the .5 reducer throws it's focus point..


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#4 tomwall

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Posted 06 December 2018 - 03:13 PM

Denny,

I'll give my Barlow without the lens element.

 

Thanks,

Tom



#5 mikenoname

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Posted 10 December 2018 - 08:06 PM

I'm fairly certain you guys are going the wrong way. Insufficient back focus is the issue. The EP port is too long to allow the camera with FR to reach focus.

 

https://www.cloudyni...and-the-etx-70/


Edited by mikenoname, 10 December 2018 - 08:11 PM.



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