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AFOV of micro-eyepieces

Eyepieces
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#1 ECP M42

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Posted 16 May 2021 - 08:22 AM

I am looking at a pair of WF15x (Ø16mm) micro-eyepieces with diopter, to be inserted in binoculars ... but how do I know the AFOV?

 

If the value of 16mm is the diameter of the field diaphragm, these mark 52 ° ISO. Far from being Wide Field.What am I missing?

 

Thank you all!


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#2 j.gardavsky

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Posted 16 May 2021 - 08:55 AM

Hello Henry,

 

anything above 50° is regarded in the microscopy as wide field.

If the inscription on the eyepiece is like 15x/16 then 16 should be the aperture of the field stop in mm.

The 15x magnifying microscope eyepiece has the focus length 250mm/15=16.7mm

 

Otherwise, why not to consider the Hensoldt Ferro f=15mm (AFOV  ~70°) eyepiece

https://www.ebay.de/...IxoC8tYQAvD_BwE

 

You just need to pull out the reticles.

 

Best,

JG


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#3 MisterDan

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Posted 16 May 2021 - 10:30 AM

There are very few microscope eyepieces with apparent fields larger than 55 degrees.  Most "UW" microscope oculars have apparent fields that fall in the 52-56-degree range, regardless of focal length.  Their "ultra widefield" descriptions relate to their peers and counterparts within the realm of clinical and industrial microscope eyepieces, where orthoscopic/flat fields are of primary importance and fields wider than 60 degrees are of little-to-no importance.  Obviously, they don't qualify as "ultrawide" in the realm of telescope/astronomic eyepieces.  The distortion introduced by (and inherent to) ocular apparent fields beyond 60 degrees is, essentially, a negative (if not prohibitive) aspect in a standard microscope ocular.

 

As an aside:  the widest-field microscope eyepieces I'm aware of are the Leica/Bausch & Lomb 15x Ultra W. F. (~16.7mm focal length) and Nikon's 20x/15 UW (~12.5mm focal length).  The B&L utilized a 23mm barrel.  Reichert, Cambridge, and at least one other company also sold the same model under their own labels.  Its field number is 20, which suggests an apparent field of ~62 degrees. However, its optical design utilizes an negative field pair, so an afov estimation based only on field stop diameter does not apply well enough.  Many users estimate the 15x/20's afov at 68-70 degrees.

 

Nikon's 20x/15 UW (30mm barrel) may be the only other microscope eyepiece with an afov similar (perhaps even slightly wider) to that of the Leica/B&L's apparent field.  It is rare and expensive.

 

I have seen mention of a CWF 25x/13 eyepiece by Unitron, but I've never seen a photo of one and consider its existence to be unlikely.  Perhaps it is a special-order item.

 

(Another side note for JG:  I finally found a Periplan GF 25x but have not yet had the chance to use it under the night sky. I was extremely lucky and spent less than US $40 for it.waytogo.gif )

 

Best wishes and kind regards.

Dan


Edited by MisterDan, 16 May 2021 - 10:32 AM.

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#4 ECP M42

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Posted 16 May 2021 - 10:52 AM

anything above 50° is regarded in the microscopy as wide field.

If the inscription on the eyepiece is like 15x/16 then 16 should be the aperture of the field stop in mm.

The 15x magnifying microscope eyepiece has the focus length 250mm/15=16.7mm

 

Otherwise, why not to consider the Hensoldt Ferro f=15mm (AFOV  ~70°) eyepiece

Thanks JG, great proposal. Very interesting those Zeiss eyepieces! But 16.7mm is already too short for what I have to do. I am looking for 17.5 mm wide field eyepieces (greater than 65 °).

 

I'm very interested in the Ø16mm speech. What does that mean, for sure?

I have read a few times that it describes the diameter of the ocular lens, I am a little confused.


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#5 j.gardavsky

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Posted 16 May 2021 - 12:17 PM

Thanks JG, great proposal. Very interesting those Zeiss eyepieces! But 16.7mm is already too short for what I have to do. I am looking for 17.5 mm wide field eyepieces (greater than 65 °).

 

I'm very interested in the Ø16mm speech. What does that mean, for sure?

I have read a few times that it describes the diameter of the ocular lens, I am a little confused.

Henry,

 

the 16 is the diameter of the field stop in mm.

Otherwise, there s still a mass of the old Zeiss eyepieces for the binoviewers on the microscopes, on the eBay,

https://picclick.de/...2598331654.html

the Zeiss E-Pl and W-Pl are pretty good,

https://www.cloudyni...iss-w-pl-10x23/

https://www.cloudyni...10x20-44-42-32/

 

Unfortunately the market with the Leica HC Plan and HC PlanS, and L Plan has dried out, available are those made in Singapore.

I have still those made in Germany,

https://www.cloudyni...plan-eyepieces/

 

Best,

JG



#6 ECP M42

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Posted 16 May 2021 - 12:21 PM

Hi Dan, excellent value. Thanks so much! 



#7 j.gardavsky

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Posted 16 May 2021 - 12:26 PM

...

 

(Another side note for JG:  I finally found a Periplan GF 25x but have not yet had the chance to use it under the night sky. I was extremely lucky and spent less than US $40 for it.waytogo.gif )

 

Best wishes and kind regards.

Dan

Hello Dan,

 

I have the old Leitz Periplan GF 25x, and it's contrast and sharpness performance is incredible on my microscope.

It has the CVD correction (chromatic magnification difference, CMA) for the Leitz APO Planar microscope objectives. It is always a question, how the CVD correction will match the CVD of the astronomy telescope.

 

https://www.cloudyni...ries-eyepieces/

 

On these three I have mounted collars for the 1.25" astronomy filters on the eye lens.

 

Best,

JG
 



#8 MisterDan

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Posted 16 May 2021 - 12:37 PM

Hello Dan,

 

I have the old Leitz Periplan GF 25x, and it's contrast and sharpness performance is incredible on my microscope.

It has the CVD correction (chromatic magnification difference, CMA) for the Leitz APO Planar microscope objectives. It is always a question, how the CVD correction will match the CVD of the astronomy telescope.

 

https://www.cloudyni...ries-eyepieces/

 

On these three I have mounted collars for the 1.25" astronomy filters on the eye lens.

 

Best,

JG
 

Ah! - I had wondered about those filter collars.  Since I had never seen other GFs with eye lens threads, I concluded that they were indeed custom installations.  It's very nice to know that you did the installations, yourself!  Excellent!

 

I recall your praise of the wonderful contrast and clarity provided by your 25x when viewing Saturn's Cassini Division.  I look forward to trying my own 25x in the Pentax and the Intes, but I may have to wait another week, due to unsettled weather.

 

Best regards.

Dan



#9 j.gardavsky

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Posted 16 May 2021 - 12:52 PM

Hello Dan,

 

you have a perfect memory!

 

There has been also a new version, the Leica Periplan GF 10x, now discontinued I guess, but somehow not as good.

The times have changed, and the old Leitz glass manufacturing has been sold to Corning.

 

Best,

JG




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