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ZWO ASI071 + 5x2" EFW + ZWO adapter + Canon lens = no focus?

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#1 DJL

DJL

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Posted 24 January 2021 - 11:39 AM

Hi all

I tore my rig apart to make a constellation portrait rig, with a Canon EF mount Rokinon 50mm lens instead of my telescope. Apparently the spacing is wrong and the system can't get to focus.

I am using this to connect the lens to the EFW: https://agenaastro.c...efw-eos-ii.html

I also have the ZWO filter drawer adapter to attach Canon EF mount lenses to ZWO ASI cameras.

Of course, to switch to this I will have to remove the EFW, which is the single worst thing about it - 8 screws to remove the cover plate, 4 screws to unbolt from the camera (which I manage to do through an unused filter hole).

This adapter is supposed to work for the filter wheel and Canon lenses, so can anyone comment on what's wrong and whether anything exists that could make it work?

Attached photos of the rig, which adds guide scope mount to the ASIAIR Pro's existing responsibilities. I always think it's cheating to use Arca-Swiss to connect astrophotography gear, but some of the screws I had to connect things were too short and ASIAIR Pro's case being sized to fit into Arca-Swiss clamps made it possible. 

 

Attached Thumbnails

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Edited by DJL, 24 January 2021 - 01:10 PM.

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#2 DJL

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Posted 24 January 2021 - 01:22 PM

From the camera manual: "The M42 female flange to the sensor is 17.5mm. You can reach 55mm back focus distance with the 21mm and 16.5mm extender included in the camera package."

EFW - 20mm

Adapter - 11.5mm

Total = 49mm, looks like it's 6mm short of the back focus distance.

 

Edit: Canon lens needs 44mm not 55mm. So this arrangement is 5mm too big.

 

Plan B: ZWO camera to EOS lens filter drawer.


Edited by DJL, 24 January 2021 - 02:07 PM.


#3 DJL

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Posted 24 January 2021 - 03:30 PM

Plan B worked. The downside is a filter drawer with just one filter holder means unscrewing and replacing filters on the fly during a session. I tried this about once before getting my filter wheel.

 

Plan C would be to remove the ASI071 tilt plate to recover the 5mm space, however this would leave the sensor exposed to the moisture in the air rather than its sealed chamber. 




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