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C-Mount lenses & filters

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#1 AllStarez

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Posted 03 April 2021 - 12:19 PM

Since i get an Ovni-M device from Jonathan’s company (« Joko » in CN), i came to use more and more camera lenses: easier and faster to use, lightweight. This is the best compromise that I have found and that I often enjoy using (and the best one when the sky is clear and that i dont have much time).

 

I mainly use M42/T2 lenses, with a filter changer (https://www.cloudyni...lchargerslider/), but i also have a few c-mount fast lenses which i really (really) enjoy : a Cosmicar TV 75mm f/1.4 (2,9/3x.) and a superb Computar MC TV 135mm f/1.8 (which gives 5,2x.)

 

Only (big) problem with the c-mount lenses is i could not use any filter with any of them : the setup has to be really short to reach focus; the filter changer doesnt work, nor short adapters (10mm width).

 

Then i asked some CN members some help, and Ray (aka GeezerGazer) found the perfect solution :

Make a filter small enough to fit inside the C-mount cavity on my Ovni-M.

In this « yellow part » cavity exactly :

 

8-F98338-F-0419-4093-A8-E1-9-EC5-EE7-E5-

 

Astronomik propose unmounted filters (12nm and 6nm) of 27mm, that would fit perfectly in there, with a rubber o-ring to avoid problem (they also propose tailor-made filters in the dimensions you want).

 

Later i have found, thanks to Jonathan who did a few tests with his equipment, that i could actually unmount my 1.25 filters myself (which i didnt know...) :

 

06-A083-A4-4038-4223-9-DDA-39665-BDB2-BB

 

I did the same with my H-Alpha 7nm and the diameter is exactly 27mm, enough to fit in my Ovni-M device :

 

DE7106-F3-4516-4-C30-A35-A-A5-AB1-C6-F5-

 

1-E7-F3-F74-A321-4-BD0-B94-A-5-CAE237-FE

 

Yes, there are certainly drawbacks to using unmounted filters, but it's a real victory in itself to be able to see the sky with a c-mount fast lens AND filters. And as far as I know there is no other way to do it so well (Except with 2’ filters, but with less visual result due to the space between the filter and the NV captor).

 

I’d like to thanks Ray and Jonathan for their precious help and time. Now i can use my c-mount lenses and enjoy them perfectly.

 

cheers


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#2 GeezerGazer

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Posted 04 April 2021 - 03:20 AM

Thanks for the shoutout AllStarez, but it was CNer Longbond who developed the idea of using a filter inside the C-mount well, so the credit belongs to him.  I'm glad you are able to filter your C-mount lenses and it was a pleasure working with you to overcome the issues.  Clear Skies. 


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#3 bobo99

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Posted 04 April 2021 - 09:13 PM

Very exciting! Will be using this with my omni-m when it arrives soon.

 

Looking at getting the Cosmicar as well. What's the difference between the Black and silver versions of the lens ?



#4 AllStarez

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Posted 05 April 2021 - 02:43 AM

Thanks for the shoutout AllStarez, but it was CNer Longbond who developed the idea of using a filter inside the C-mount well, so the credit belongs to him.  I'm glad you are able to filter your C-mount lenses and it was a pleasure working with you to overcome the issues.  Clear Skies. 

 

Thanks to Longbond then waytogo.gif

i used all my c-mount lenses with success yesterday night. Now i can make the most of it with my filters, and oh i so love it


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#5 AllStarez

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Posted 05 April 2021 - 02:45 AM

Hello bobo99

no idea about the silver version of the lens which has the same characteristics, but it should weight more i suppose ? I just  know Cosmicar produced this 75mm lens for some time.


Edited by AllStarez, 05 April 2021 - 06:34 AM.


#6 PEterW

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Posted 05 April 2021 - 05:18 AM

Be interesting to see how the filters handle the fast light cone, how much off axis band shift there is? Nifty little discovery, I always wondered how a 1.25” would fit in my m42-c adapter....
Peter

#7 longbond

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Posted 06 April 2021 - 10:55 AM

Thanks to Longbond then waytogo.gif

i used all my c-mount lenses with success yesterday night. Now i can make the most of it with my filters, and oh i so love it

Congratulations AllStarez! I'm glad the unmounted filter setup is working for you. Ray (GeezerGazer) and I had some concerns about the C-thread sleeve in your Ovni-M, but your ability to use a stock 27mm from a 1.25" cell is a big plus. My Mod-3 requires a custom-cut 24mm dia.

 

You also have some great C-mount lenses. I have the Computar 135mm f/1.8 and you're right. It's surprisingly good! Your Cosmicar 75mm f/1.4 is also superb. I have a pair of the Pentax version and that's my main grab n go 3x lens.


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#8 AllStarez

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Posted 06 April 2021 - 11:24 AM

Be interesting to see how the filters handle the fast light cone, how much off axis band shift there is? Nifty little discovery, I always wondered how a 1.25” would fit in my m42-c adapter....
Peter

I never had troubles using 1.25 filters with c-mount or M42 lenses and i dont know much more about the technical parts, sorry. The good thing with the c-mount lenses is that i fix the filter right in front of  the NV’s lens



#9 AllStarez

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Posted 06 April 2021 - 11:31 AM

Thanks Longbond!

Thats great i dont have to order tailored filters from Astronomik... what a relief. i just received a 3.5nm this morning and i cant wait to try it.

 

And yes that Computrar 135mm f1/8 is magic, even if a bit heavy :) have you tried any other c-mount lenses ? I really do like these fast lenses better than my old Nikkor or Canon. I’ve seen a 50mm f0.95 and still thinking buying it some day...


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#10 longbond

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Posted 06 April 2021 - 12:19 PM

AllStarez the good news is that you already have two of my favorite C-mount lenses. If someone advised you, you got excellent advice! My other C-mount lenses are okay, but not as good as your two. The one I'd avoid is the Cosmicar 22.5-90mm f/1.5 zoom. That one is pretty bad. It's also very heavy. That's unfortunate because it's very fast for a zoom.

 

For me, C-mounts lenses are mostly for fun, but used manual camera lenses are usually better. They're designed for a larger image circle and are widely available at great prices.

 

If I were you, I'd declare victory. You're in great shape!


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#11 AllStarez

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Posted 06 April 2021 - 01:47 PM

Haha thanks, i’ll keep them preciously, no worry :)

Which camera lenses you are thinking about, in the 50 to 200 range ? I just kept a few of them, mainly a Cyclop Helios 100mm f/2 and a Owen Automatic 135mm f/2.8 for its small size



#12 longbond

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Posted 06 April 2021 - 03:34 PM

Seriously, just about any SLR camera lens is good for NV if it's reasonably fast. Most of my camera lenses are Nikons. I also have a Rokinon 24mm f/1.4, but it's unnecessarily big and heavy for NV. I like my small Envis lens a lot better at 1x.

 

Ray (GeezerGazer) and I both have the Nikon 50mm f/1.4 and really like them. A lot of people on CN have the Nikon 180mm f/2.8 and love them. I do too. It's one of the all-time best lenses for photography and Nikon has been making them (with the same optical design) since the Stone Age smile.gif


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#13 AllStarez

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Posted 11 April 2021 - 04:10 AM

Seriously, just about any SLR camera lens is good for NV if it's reasonably fast. Most of my camera lenses are Nikons. I also have a Rokinon 24mm f/1.4, but it's unnecessarily big and heavy for NV. I like my small Envis lens a lot better at 1x.

 

Ray (GeezerGazer) and I both have the Nikon 50mm f/1.4 and really like them. A lot of people on CN have the Nikon 180mm f/2.8 and love them. I do too. It's one of the all-time best lenses for photography and Nikon has been making them (with the same optical design) since the Stone Age smile.gif

I already had that 180mm lens and pretty liked it, but I did not find practical to use filters with (my filter changer didnt work, but it did with M42/T2 camera lenses)




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