Wild M4520 or M400: which 3rd party 10x eyepiece

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zzffnn
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Wild M4520 or M400: which 3rd party 10x eyepiece

#1 Post by zzffnn » Sat Mar 04, 2023 2:48 pm

What is a good 3rd party 10x eyepiece for Wild M400 or M420, please? I prefer good parfocality (doesn’t have to be perfect) on M400/M420 and field number of close to 25mm. Would most focusable finite eyepieces work? Thank you.

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Re: Wild M4520 or M400: which 3rd party 10x eyepiece

#2 Post by apochronaut » Sat Mar 04, 2023 4:49 pm

You might try Martin Microscope on that, unless someone else on the forum knows for sure or the Wild facebook group.. Martin does a bit of experimenting and might have tried other eyepieces in those Macroscopes. They are usually helpful. I have dealt with Aaron , I think it as.
Eyepieces are a crapshoot because they are on a continuum of strongly corrective through neutral to strongly compensating. Add to that, any negative through to positive field curvature adjustments and it is easy to see that non native eyepieces need to be tested by someone, not just picked off a chart, especially when you are seeking a 25mm f.o.v. and presumably flat and well corrected. As the diameter of the field increases, the degree of correction/compensation required at the periphery increases.
Given the date of manufacture of those and the fact that it is a Wild, I would guess the eyepieces are compensating but anything is possible. My starting point to test how much it needs would be eyepieces that are strongly compensating, such as those old Olympus Bi WF10X, which I would guess overcompensate. Less compensating would be AO # 145. AO # 146 are almost neutral. You have all those, don't you.
Modern generic Chinese eyepieces, like those ones that are everywhere with the convertible tube diameter and field stop are pretty neutral, similar to # 146 eyepieces. I could test the two together and get a reading on how they compare, so then you could use your tests with the #146 on your Wild as a bench mark.
I do have one Wild stereo eyepiece I keep as a test eyepiece, marked Wild Heerbrugg 10X. I think it is for an M5 but I am not certain. It is about 24mm f.o.v. and is a correcting type.
The ones I would be targeting aside from original Wild eyepieces, which I know are very expensive, would be Leitz 30mm, Reichert 30mm from the Univar or Polyvar or the 30mm from the BS-3091. They seem a little different than those generic neutral ones but could be built to the same curves. I haven't compared them. They are 23mm f.o.v.
I can do some checking on what I have compared to say the, #146 and the Olympus Bi. That would give you a bench mark.

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Re: Wild M4520 or M400: which 3rd party 10x eyepiece

#3 Post by Scarodactyl » Sat Mar 04, 2023 6:55 pm

The eyepieces are not particularly compensating for the record (direct projection is the favored method for photography after all), but they want to sit lower in the tube than other brands which is what makes it so annoying. Iirc the M450 might be compatible with normal m series eyepieces, but they made special short stubby ones for the m400.
I don't think Wild made 24mm fov eyepieces for the M5(?). I would love to see that, maybe some rare component from the early days? I have a wild 5x eyepiece which I've also had trouble finding documentation on. All the Wild stereo eyepieces I have seen topped out at 21mm, even on the M10 (though they can usually cover a lot more depending on your configuration). The typical 10xes also don't apply much in the way of correction, though like Nikon they offered them in different quality tiers so the cheaper ones probably introduce some aberrations.

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Re: Wild M4520 or M400: which 3rd party 10x eyepiece

#4 Post by apochronaut » Sat Mar 04, 2023 10:39 pm

This 10X I have is slightly correcting. I will compare the field to the Polyvar 30mm eyepieces which are 24mm f.o.v. and report back. My assessment is just by looking through one in comparison to a 20mm but it seems quite wide.

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Re: Wild M4520 or M400: which 3rd party 10x eyepiece

#5 Post by apochronaut » Sun Mar 05, 2023 12:56 am

That Wild 10X turns out to be a 23mm f.o.v. eyepiece, perfectly matching the field of the BS-3091 10X/23mm. That Chinese eyepiece might be an option for you Fan. I can't locate my price list for accessories ftom 2 years ago but at one time a pair was 140.00 or maybe 150. They have a very short insert section since Scarodactyl has pointed out that requirement.
The 10X Wild eyepiece I have here has an insert section of 31m length. The BS-3091 eyepiece has an insert section 22mm long. The field diaphragm is threaded in the bottom and with that removed the section is 19 1/2mm and the field enormous, about 28mm, maybe more . I don't know how flat that extra field would turn out to be on your microscope or whether your optical tube is in fact more than 23mm. That is the limiting factor, not necessarily the eyepiece.
Last edited by apochronaut on Mon Mar 06, 2023 2:11 pm, edited 1 time in total.

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Re: Wild M4520 or M400: which 3rd party 10x eyepiece

#6 Post by zzffnn » Sun Mar 05, 2023 3:31 am

Thank you very much, gents.

Apochronaut’s measurements are especially helpful to me. I will do some additional test and measurements.

Scarodactyl has lots of experience with Wild M4X0 scopes and has been kindly helping me on this project.

Interestingly, I thought about removing the back diaphragm of my Olympus eyepiece, while I was fixing its solidified grease problem/

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Re: Wild M4520 or M400: which 3rd party 10x eyepiece

#7 Post by apochronaut » Tue Mar 07, 2023 5:07 pm

Here are a couple of photos of the Wild 10X mentioned above and the 10X/23mm used on the BS-3091. The insert section on the Chinese eyepiece is quite short as described.

I did some testing with several eyepieces as well in order to determine where they sit on the correction/compensation scale. I used an AO cat. # 146 eyepiece as a benchmark, since I know you have those. The #146 is a very neutral eyepiece leaning towards being slightly correcting, which means that it still slightly under corrects with the achromat 10X .25 objective that it was originally mated to : although it is very slight and only seriously affects the extreme periphery of it's 19mm field. The reason for this undercorrection is that it would have been very expensive to bring all the objectives in the range including higher N.A. versions and fluorites to the same state of correction in 1955, so eyepiece correction with achromats was somewhat sacrificed and averaged being usually centered on one objective ( often the 40X), with the others drifting slightly away from the realized ideal. This slight malcorrection at the periphery with the 10X is useful as a tool in order to compare other eyepieces.
So, in comparison to the #146, the following eyepieces give varying degrees of correction.
1) Wild 10X 30mm bore as pictured here. About the same as the # 146, or perhaps slightly less correcting but so little that it is almost unperceptible. So as Scarodactyl indicated, in the neutral zone. None focusing.
2) Chinese made generic eyepiece. Convertible in both bore size and with limitations the field too. Supposedly has a field over 25mm when a 30mm insert tube is used. Focusable. This eye piece is more neutral than either the #146 or the Wild 10X.
3) Chinese made factory eyepiece for the BS-3091 stereo microscope. 10X/23mm 30mm bore. This eyepiece is slightly compensating, likely due to it being mated to a planapo objective.
4) As a control and also one which I think you are familiar I also tested the Olympus Bi WF10X used with short barrel Olympus apochromat objectives. Very compensating, so terribly undercorrecting compared to the #146, as well as all the other objectives.
Two photos below.
1) BS-3091 eyepiece on left, AO #437 focusing measuring eyepiece in the middle and Wild 10X 30mm eyepiece on right. The AO #437 is a fairly large eyepiece with an external focusing worm, so I used it for a size comparison.
2) Showing the difference in insert tube length.
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Re: Wild M4520 or M400: which 3rd party 10x eyepiece

#8 Post by zzffnn » Wed Mar 08, 2023 1:50 am

Thank you very much, Phil.

When you said:

Quote

2) Chinese made generic eyepiece. Convertible in both bore size and with limitations the field too. Supposedly has a field over 25mm when a 30mm insert tube is used. Focusable. This eye piece is more neutral than either the #146 or the Wild 10X.

Unquote

How do I find that Chinese generic eyepiece, please? When you have a chance, would you mind sharing photos of it, or let m elbow its catalog number? Sometimes there are different versions. I see lots of Chinese focusable 30mm tube FN22 10x EPs, but few FN23.

The BS-3091 eyepiece is not easy to find and not cheap for its limited field number.

What is the approximate field number for AO 437 on your BestScope, please? I searched but found no answer; they are easily available on eBay, at least.

My eyes are bad and highly prefer wide field and high eye points; I will pay up for field width.

Forum member Eiman kindly sold me a pair of Nikon CFUWN 10x FN 26.5 focusable eyepieces at great price and allows me to return if parfocality does not work on Wild M450. So I would try them first and report back, if I get to test them before I leave town on Saturday.

Yes, insertion length of 22x for 10x is quite short. My Olympus 15x EPs work best with Wild M450 at “-8” or insertion depth of 16mm; parfocality is ruined, if I extend the same EPs to “+5” or 21mm.

The huge B&L UWF 15x has a long insertion depth (of 27mm with glass element close to bottom) and doesn’t work with parfocality of the M450. The UWF is an extreme and unusual eyepiece though, it is fully packed with glass elements inside.

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Re: Wild M4520 or M400: which 3rd party 10x eyepiece

#9 Post by apochronaut » Wed Mar 08, 2023 12:09 pm

zzffnn wrote:
Wed Mar 08, 2023 1:50 am
Thank you very much, Phil.

When you said:

Quote

2) Chinese made generic eyepiece. Convertible in both bore size and with limitations the field too. Supposedly has a field over 25mm when a 30mm insert tube is used. Focusable. This eye piece is more neutral than either the #146 or the Wild 10X.

Unquote

How do I find that Chinese generic eyepiece, please? When you have a chance, would you mind sharing photos of it, or let m elbow its catalog number? Sometimes there are different versions. I see lots of Chinese focusable 30mm tube FN22 10x EPs, but few FN23.

The BS-3091 eyepiece is not easy to find and not cheap for its limited field number.

What is the approximate field number for AO 437 on your BestScope, please? I searched but found no answer; they are easily available on eBay, at least.

My eyes are bad and highly prefer wide field and high eye points; I will pay up for field width.

Forum member Eiman kindly sold me a pair of Nikon CFUWN 10x FN 26.5 focusable eyepieces at great price and allows me to return if parfocality does not work on Wild M450. So I would try them first and report back, if I get to test them before I leave town on Saturday.

Yes, insertion length of 22x for 10x is quite short. My Olympus 15x EPs work best with Wild M450 at “-8” or insertion depth of 16mm; parfocality is ruined, if I extend the same EPs to “+5” or 21mm.

The huge B&L UWF 15x has a long insertion depth (of 27mm with glass element close to bottom) and doesn’t work with parfocality of the M450. The UWF is an extreme and unusual eyepiece though, it is fully packed with glass elements inside.

I just included the #437 as a size reference. It is the focusable version of the #180. 20mm f.o.v., so not relavent as a functional eyepiece for you.

Here is the generic Chinese made eyepiece https://www.ebay.ca/itm/114029776896?_t ... %3A2047675

The insert section threads out and the field stop diameter can be altered up to maybe 26mm or so. I'm not sure what the peripheral characteristics are at that field, though. In the listing there are both 22mm f.n. and 23mm f.n. They are the same eyepiece optically, just with a different diameter insert tube. The 22mm version uses a 23.2mm insert tube and the 22mm i.d. of the insert tube becomes the field stop. The 23mm version uses a 30mm insert tube and there is a 23mm field stop inside it.
It is not the same eyepiece as that used on the BS-3090 which seems be tuned to the instrument's planapo objective. The generic eyepiece is quite neutral .

Since that line of Wild instruments had an original f.n. of 21, are the pisms large enough to carry a huge f.o.v.?
I have had quite a few microscope heads apart and usually the optical tube is pretty tight to the target f.o.v. It would be uneconomical to make heads otherwise. Notably, several manufacturers produced alternate U.W.F. heads for U.W.F. fields.

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Re: Wild M4520 or M400: which 3rd party 10x eyepiece

#10 Post by zzffnn » Fri Mar 10, 2023 10:14 pm

Nikon CFUWN 10x FN26.5 works perfectly on my Wild M450, with or without 0.5x or 2x aux lens. Parfocality is almost perfect.

I did not have time to “pixel peep” photos at at field peripherals, but visually the view field is flat, resolution is very good and CA is minimal.

With 1x stock zoom objective set to lowest “16” magnification, width of view field is about 32mm. With 0.5x aux lens (the generic Chinese lens), width of view field is about 61.5mm. Image quality is very good.

The Nikon has no back diaphragm to be easily removed (for the purpose of increasing view field). Not that it is necessary. I already have to kind of roll my eye balls with the wide field.

Insertion depth of the Nikon is about 23mm at its shortest focus. And it has a glass element at very close to its bottom.

Neither Olympus Bi WF10x or AO Spencer #146 work very well for parfocality on the Wild M450 (both are quite a bit worse than Olympus 15x WHSZ15x-H/16 in terms of parfocality, though a bit better than the long and huge B&L UWF 15x). Both are kind of short with 22mm and 25 mm insertion depth, respectively.

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Re: Wild M4520 or M400: which 3rd party 10x eyepiece

#11 Post by einman » Sat Mar 11, 2023 1:57 am

I'm glad you received the eyepieces, and they worked out for you Fan. I had them for some time as a back-up for one of my Leitz scopes. But I'm trimming down my collection in light of retirement and subsequent changes.

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