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Aperture mask for canon 2.8/200

astrophotography accessories dso refractor
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#1 GTom

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Posted 16 December 2019 - 08:04 AM

I need a quick solution to stop down my 2.8/200 before the step-down ring kit arrive from fleabay (weeks...). Anyone used a simple cardboard mask on camera lenses? I know many do that with refractors for solar work.



#2 mastersniper

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Posted 16 December 2019 - 08:24 AM

I assume this is to mount the lens to a astro camera via adapter.  If so there is no need for a mask, assuming you have canon body.  Attach lens to EOS body, turn on camera, set aperture to whatever say F5.6, turn on live-view, detach lens, blades stay stopped down turn off body. At least the several canon lenses I have operate that way so I assume the 200/f2.8 would as well.



#3 GTom

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Posted 16 December 2019 - 08:41 AM

Forgot, it's a 6D and I also use a nikon z6 with a dumb EF-Z adapter (no electrical contact), aperture setting would be of course obvious but I would like to get rid of the diffraction spikes coming from the blades.


Edited by GTom, 16 December 2019 - 08:56 AM.


#4 2ghouls

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Posted 16 December 2019 - 08:53 AM

Should be possible. If you don’t want any kind of diffraction spikes, you will need a pretty perfect cut. You can get a compass-style circular paper cutter at a craft store. That’s what I use for making solar filters.
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#5 GTom

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Posted 16 December 2019 - 09:07 AM

Thank you, I'll try it waytogo.gif



#6 GTom

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Posted 16 December 2019 - 03:54 PM

I assume this is to mount the lens to a astro camera via adapter.  If so there is no need for a mask, assuming you have canon body.  Attach lens to EOS body, turn on camera, set aperture to whatever say F5.6, turn on live-view, detach lens, blades stay stopped down turn off body. At least the several canon lenses I have operate that way so I assume the 200/f2.8 would as well.

Tried, works waytogo.gif , should be ok for my 1.4/20 sigma, where I don't worry about diffraction spikes. Is it OK to leave the aperture stopped down for weeks? The 6D body doesn't come with me all the time.



#7 mastersniper

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Posted 18 December 2019 - 03:05 AM

Tried, works waytogo.gif , should be ok for my 1.4/20 sigma, where I don't worry about diffraction spikes. Is it OK to leave the aperture stopped down for weeks? The 6D body doesn't come with me all the time.

I figured out this 'trick' by accident left my 70-200 stopped down for a few months with no noticeable issues still using it 6 years later just fine.


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