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Difficulty focusing camera with barlow

Astrophotography Imaging Equipment
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#1 Jmmaddox

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Posted 07 December 2022 - 05:53 PM

Hi Group, can I ask for some help please. I tend to do DSO imaging but do try my hand at planetary every now and again. Setup for this is Skywatcher ED80 (with Baader steeltrack focuser), celestron 2x X-CEL barlow and ZWO ASI 120mc camera. Without the barlow I can get into focus by using about 8cm of T2 extenders at the end of the fully extended focuser. With the barlow I can't focus at all.
Sure others must have a similar setup and have solved the problem, so I wanted to ask for help before going out to buy more and more extenders.
Thanks

#2 hyiger

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Posted 07 December 2022 - 06:37 PM

Hi Group, can I ask for some help please. I tend to do DSO imaging but do try my hand at planetary every now and again. Setup for this is Skywatcher ED80 (with Baader steeltrack focuser), celestron 2x X-CEL barlow and ZWO ASI 120mc camera. Without the barlow I can get into focus by using about 8cm of T2 extenders at the end of the fully extended focuser. With the barlow I can't focus at all.
Sure others must have a similar setup and have solved the problem, so I wanted to ask for help before going out to buy more and more extenders.
Thanks

Lots and lots of spacers is what I needed. 



#3 Jmmaddox

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Posted 07 December 2022 - 07:09 PM

Thanks, I would have thought that the barlow might bring the focus point closer, which is why I wasn't sure if getting more spacers was the right way forward. Maybe it is back to AliExpress to get some more.

#4 c2m2t

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Posted 07 December 2022 - 07:57 PM

Hi Jmmaddox!

If I recall correctly, your scope is F7. I am guessing that you are able to focus an eyepiece with the barlow and a diagonal...correct?? If that is indeed the case, and assuming you are imaging straight through, you are effectively trying to make up for the removal of the diagonal from the setup. Many spacers can be more practically handled with a 2" extension tube which should make up for the diagonal that has been removed.

 

Cheers, Chris.


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#5 Jmmaddox

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Posted 07 December 2022 - 08:47 PM

Thanks Chris, no diagonal, just scope to camera +/- barlow in between. I presume the diagonal does a similar job to the spacers by adding a bit more distance between barlow and camera

#6 c2m2t

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Posted 07 December 2022 - 10:20 PM

Hi Jm!

I realize you are not using the diagonal for imaging...I was only drawing the similarity to using an eyepiece and coming to focus. The camera is effectively your eye and if the eye can focus with the barlow and diagonal, to image with the camera and removal of the diagonal, the diagonal needs to be replaced by a similar length of light path....and that would be the 2" extension...or thereabouts.

 

Cheers, Chris.




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