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Mounting DSLR lens

DSLR Mount
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5 replies to this topic

#1 zlevay

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Posted 20 June 2021 - 08:12 PM

I'm looking thoughts on how to mount a large SLR lens on an equatorial mount, specifically a Nikon 200-500mm f/5.6 on an iOptron CEM25P. I've not been able to get good tracking/guiding using the Nikon supplied collar screwed to a dovetail bar. I think there's too much flexure; though it may just be too heavy to get good balance, especially when extended to 500mm (but at just over 5lb (2.6kg), minus camera, etc. it ought to be well within the mount's capacity).

 

I'm thinking a pair of mounting rings attached to a dovetail plate might work but not sure what the best options are. Using a pair of large hose clamps might work but seems pretty kludgy and not sure how best to fasten that to the bar. Rings for finder/guide-scopes don't seem sturdy enough for this rather heavy lens. Tube rings for telescopes would seem to be ideal, but more expensive and not sure they will fit precisely enough -- and I need two different sizes. Looks like the places on the lens I can safely attach a ring are pretty close to 80mm (3-1/8in) and 100mm (4in) in diameter.

 

Hmmm, maybe if I had access to a 3D printer or CNC machine... 

 



#2 B 26354

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Posted 20 June 2021 - 08:47 PM

Hmmmm...  given its weight of 2.3kg... the fact that its body is made almost entirely of plastic might account for a good bit of flexure.

 

https://www.kenrockw...n/200-500mm.htm

 

Also... the metal mounting collar only has one mounting-hole. I'd be tempted to drill-&-tap a second one, so that alignment with a Vixen dovetail would be less apt to shift.

 

grin.gif


Edited by B 26354, 20 June 2021 - 08:48 PM.


#3 whwang

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Posted 20 June 2021 - 11:00 PM

IMG_9825.jpg

 

This is how I mount a heavy telephoto lens (on a Vixen-style dovetail plate).


  • B 26354, vidrazor, brlasy1 and 2 others like this

#4 galacticinsomnia

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Posted 21 June 2021 - 01:34 AM

I was going to say a long dovetail bar mounted Similar to the above.  The Spotting or telescope mount is a neat idea and I'm sure it could work, I would rather just get the dementions and makes something out of wood or Delrin that would be a really stable mount.

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#5 zlevay

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Posted 25 June 2021 - 01:31 PM

Thanks for the comments. I was able to jury-rig an attachment using a hose clamp in addition to the tripod collar on a dovetail bar. This made the assembly much more stable and balances nicely. I was finally able to test it and took 5-minute exposures (guided) with no trailing. I'd love to find a less kludgy solution, perhaps fabricate something from wood or investigate 3D printing.

 

200-500mm

Edited by zlevay, 25 June 2021 - 01:32 PM.


#6 KLWalsh

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Posted 26 June 2021 - 09:47 AM

Maybe you could find a scope ring that matches the diameter of your lens barrel. A finder ring would be similar option. Even a small embroidery hoop might work, attached the way the hose clamp is attached.
But if you can 3D print something, that might be your ideal solution.


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