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Antique Steinheil monocentric

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#26 SandyHouTex

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Posted 31 May 2020 - 11:50 AM

Hello all for reminding the monocentric design!

 

Here is the Steinheil monocentric triplet lens in my collection of old optics,

 

attachicon.gifSteinheil monocentric with conical mount.jpg

 

The diameter of the front lens is 13.8mm, the total length is 24.5mm .

 

Best,

JG

Oh my.  My holy grail.  Have you looked through it?



#27 j.gardavsky

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Posted 31 May 2020 - 12:14 PM

Oh my.  My holy grail.  Have you looked through it?

Yes,

it is a relatively large piece of optics.

Taking it just as a magnifier, the view is still very sharp, clear and crisp, even if the cements show at the lenses rims some aging. The outer blackening is remarkably intact.

 

Best,

JG


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#28 SteveC

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Posted 31 May 2020 - 01:27 PM

Edmund Optics sells Steinheil lenses. I considered playing around with it when I was making my ball eyepieces.  Never got around to pulling the trigger though, $100 - $120 each. 

 

https://www.edmundop...ns&Tab=Products



#29 SandyHouTex

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Posted 31 May 2020 - 02:36 PM

Edmund Optics sells Steinheil lenses. I considered playing around with it when I was making my ball eyepieces.  Never got around to pulling the trigger though, $100 - $120 each. 

 

https://www.edmundop...ns&Tab=Products

And this is where issues come in.  A monocentrice eyepiece is named that way because all three lenses radii of curvature converge at one point, both from a positive and negative sense.  All of the current supermonocentrics and the like are just Hastings Triplets.  NONE of the elements radii coincide.  It’s another example of manufacturers branding an inferior eyepiece with a superior name.  Another instance is that all of the Plossls made and sold today are simple Symmetricals.  A true Plossl has three different types of glass, and the two achromatic doublets are not the same.

 

That’s why I’d give my left kidney for one of the antique brass monocentrics being shown in the photographs above.  They are considered to be the ultimate planetary eyepiece.  Interestingly enough, even the vaunted Zeiss sold the fake monocentric.

 

TRUE MONOCENTRIC                 FAKE MONOCENTRIC

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Edited by SandyHouTex, 31 May 2020 - 02:48 PM.

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#30 RichA

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Posted 31 May 2020 - 02:53 PM

And this is where issues come in.  A monocentrice eyepiece is named that way because all three lenses radii of curvature converge at one point, both from a positive and negative sense.  All of the current supermonocentrics and the like are just Hastings Triplets.  NONE of the elements radii coincide.  It’s another example of manufacturers branding an inferior eyepiece with a superior name.  Another instance is that all of the Plossls made and sold today are simple Symmetricals.  A true Plossl has three different types of glass, and the two achromatic doublets are not the same.

 

That’s why I’d give my left kidney for one of the antique brass monocentrics being shown in the photographs above.  They are considered to be the ultimate planetary eyepiece.  Interestingly enough, even the vaunted Zeiss sold the fake monocentric.

 

TRUE MONOCENTRIC                 FAKE MONOCENTRIC

Except Brandon.



#31 j.gardavsky

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Posted 31 May 2020 - 03:11 PM

Hello Sandy,

 

yes, the Zeiss in the right pic is just a (symmetric) triplet, even if there is the letter M on the Zeiss body, letting the innocent people believe they are buying a monocentric.

 

At f=25mm, the true Steinheil monocentric with its big field lens in the otherwise slim triplet would be looking like a pear.

 

I have the Leitz f=42mm symmetric triplet, already resized for 1.25", but it is still waiting on the first light from the stars.

 

Best,

JG



#32 stevep

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Posted 31 May 2020 - 03:25 PM

Hello all for reminding the monocentric design!

 

Here is the Steinheil monocentric triplet lens in my collection of old optics,

 

attachicon.gifSteinheil monocentric with conical mount.jpg

 

The diameter of the front lens is 13.8mm, the total length is 24.5mm .

 

Best,

JG

Great to see another has survived,

 

Interesting to see that the lens elements/ shapes and proportions are different to mine, I had always assumed that different FL would look different,

do you have an idea on the FL of yours ?

 

Steve


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#33 j.gardavsky

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Posted 31 May 2020 - 04:00 PM

Hello Steve,

 

I have not checked the focus length.

Now, the triplet is back in the conical tube, and tomorrow, I can make a rough estimate of the front lens distance to the focus plane.

 

Best,

JG



#34 SandyHouTex

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Posted 31 May 2020 - 05:48 PM

Hello Sandy,

 

yes, the Zeiss in the right pic is just a (symmetric) triplet, even if there is the letter M on the Zeiss body, letting the innocent people believe they are buying a monocentric.

 

At f=25mm, the true Steinheil monocentric with its big field lens in the otherwise slim triplet would be looking like a pear.

 

I have the Leitz f=42mm symmetric triplet, already resized for 1.25", but it is still waiting on the first light from the stars.

 

Best,

 

You are quite lucky to be in Europe and have access to all of those wonderful antique astronomical optics.
 


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#35 SteveC

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Posted 31 May 2020 - 05:58 PM

How are the Supermonos and the Zeiss monocentrics inferior? Has anyone compared the three eyepieces mentioned? I have observed with two of the three and sense "inferior" to be a bit extreme. 

 

Wouldn't "different" be a more appropriate word than "fake"?


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#36 SandyHouTex

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Posted 31 May 2020 - 06:30 PM

How are the Supermonos and the Zeiss monocentrics inferior? Has anyone compared the three eyepieces mentioned? I have compared two of the three and sense "inferior" to be a bit extreme. 

 

Wouldn't "different" be a more appropriate word than "fake"?

Nope.  Like I said, a MONOCENTRIC eyepiece by definition, is an eyepiece where the optical elements all have the same radii of curvature.  A Hasting triplet doesn’t.  Nor does a Steinheil triplet.  You can use any word that you want, but the triplets are NOT Monocentrics.

 

Amd if you send me a true Monocentric, a TMB Supermonocentric (which is a Hastings triplet), and a Zeiss eyepiece labeled Monocentric (again another Hasting triplet), I’ll e glad to compare them and let you know.

 

Here’s a great discussion on Monocentric versus Hastings triplet by Chris Lord:

 

http://www.brayebroo...ofEYEPIECES.pdf
 

Pages 23, 24, and 25.  In it Chris says, “These (true Monocentrics) are the most nearly perfect eyepieces ever designed, having highly corrected achromatic and orthoscopic fields, flat over the greater part, and very dark.”


Edited by SandyHouTex, 31 May 2020 - 06:32 PM.

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#37 stevep

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Posted 31 May 2020 - 06:41 PM

Hello Steve,

 

I have not checked the focus length.

Now, the triplet is back in the conical tube, and tomorrow, I can make a rough estimate of the front lens distance to the focus plane.

 

Best,

JG

Hi, JG

 

Conical tube, is this what the lens sits in, do you have the original brass metal/housing like mine ?

 

Steve


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#38 SteveC

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Posted 31 May 2020 - 07:52 PM

 

Amd if you send me a true Monocentric, a TMB Supermonocentric (which is a Hastings triplet), and a Zeiss eyepiece labeled Monocentric (again another Hasting triplet), I’ll e glad to compare them and let you know.

 

That's  okay, I've already compared a bunch of true monocentrics(2.9mm, 4.4mm, 5.9mm, 7.4mm spheres) to both the Zeiss and TMB Hasting triplets, aka fake monocentrics. The sphere eyepieces are excellent, and that's all I want to say about them. I use them all the time for planetary observations.



#39 SandyHouTex

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Posted 31 May 2020 - 09:56 PM

That's  okay, I've already compared a bunch of true monocentrics(2.9mm, 4.4mm, 5.9mm, 7.4mm spheres) to both the Zeiss and TMB Hasting triplets, aka fake monocentrics. The sphere eyepieces are excellent, and that's all I want to say about them. I use them all the time for planetary observations.

You mean so-called “ball” eyepieces?



#40 SteveC

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Posted 31 May 2020 - 10:12 PM

You mean so-called “ball” eyepieces?

Yes. The moderators prefer I use the word "spheres". Are glass spheres not monocentric?



#41 SteveC

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Posted 31 May 2020 - 10:42 PM

Yes, another CN member also said this which is why I have posted it, my view is that others must have been made, I have seen pictures of some of Steinheil's other eyepieces Ortho's and Kellner's that feature in the same catalogue but no Mono's,

my guess is that two world wars in Europe may be part of the reason Steinheil eyepieces are rare, I do not think any were made after the first world war,

 

Steve

Does the catalogue have prices for Steinheil's orthos and Kellners?

 

What year was the catalogue produced?



#42 RichA

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Posted 31 May 2020 - 10:47 PM

That's  okay, I've already compared a bunch of true monocentrics(2.9mm, 4.4mm, 5.9mm, 7.4mm spheres) to both the Zeiss and TMB Hasting triplets, aka fake monocentrics. The sphere eyepieces are excellent, and that's all I want to say about them. I use them all the time for planetary observations.

Nice to see not everyone demands 20mm of eye relief in each eyepiece. 


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#43 SteveC

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Posted 31 May 2020 - 11:12 PM

Nice to see not everyone demands 20mm of eye relief in each eyepiece. 

Someday maybe, but not today.



#44 25585

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Posted 01 June 2020 - 06:11 AM

Nice to see not everyone demands 20mm of eye relief in each eyepiece. 

mad.gif


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#45 luxo II

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Posted 01 June 2020 - 08:30 AM

Would be interesting to see what could be made of the Steinheil design using modern glass types, with the help of OSLO or similar - and someone with the time to make one.

Edited by luxo II, 01 June 2020 - 08:48 AM.


#46 j.gardavsky

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Posted 01 June 2020 - 09:21 AM

Hi, JG

 

Conical tube, is this what the lens sits in, do you have the original brass metal/housing like mine ?

 

Steve

Hi Steve,

 

this Steinheil monocentric has been in a convolute of the 19th century optics and mechanics parts for the microscopes and telescopes, including Nicol polarizing prisms, focusers, lens groups for the draw tube telescopes, etc.

I have purchased the convolute for refurbishing broken or incomplete 19th century microscopes.

The Steinheil has been just in the conical cyllinder tube with a thread to become mounted into an eyepiece tube. The eyepiece tube has not been included.

 

Using the Steinheil monocentric as a magnifying glass above a ruler allowing to see both the magnified and not magnified lines,

my estimate is a magnification of 10x, which would correspond with f=25mm.

Herewith is the principal plane (Hauptebene) located very deep in the triplet, actually as expected, with just a short distance left between the field lens and the object (focus space of the telescope).

 

Best,

JG


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#47 SandyHouTex

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Posted 01 June 2020 - 09:34 AM

Yes. The moderators prefer I use the word "spheres". Are glass spheres not monocentric?

A typical Monocentric has 3 elements, so I would say no, but I’ve never owned or looked through one.  And what makes a Monocentric so awesome is the quote I posted by Chris Lord in my post #36.  If a “ball” eyepiece meets all those criteria, than I would say yes.



#48 SteveC

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Posted 01 June 2020 - 11:28 AM

A typical Monocentric has 3 elements, so I would say no, but I’ve never owned or looked through one.  And what makes a Monocentric so awesome is the quote I posted by Chris Lord in my post #36.  If a “ball” eyepiece meets all those criteria, than I would say yes.

I can draw a sphere inside the the Zeiss monocentric drawing you posted and get pretty close to a monocentric design. I propose that Zeiss and Markus Ludes designed their versions of the monocentric the way they did because shorter f/ls are extremely difficult to build. The elements are just to small in a cemented triplet if you adhere to Steinheil's design. That's why I said that the TMB and Zeiss monocentrics are different and, imho, rather ingenious designs. As far as inferior to Steinheil's design, that would be strictly conjecture. I don't think there's anyone alive that can claim to have compared both designs in comparable f/ls.

 

With all due respect to Chris Lord, I'm not convinced he actually looked through a Steinheil monocentric. If a person had ever observed though the "most perfectly corrected eyepiece " ever made,  I suspect that more would opined than "very dark". I don't even care that the TMB and Zeiss "monocentrics" aren't well corrected in my TEC140.  I'm amazed at the sharp, contrasty, and dark views in the center of the field when observing planets, star clusters, planetary nebulae, and double stars. I admit that edge correction, narrow fov, and eye relief are issues, and that observers who can't tolerate those issues should stay away from monocentrics. The monocentrics are specialty eyepieces. There's an opinion for you, believable/helpful or not, there's more substance there than Chris Lord's .

 

I am looking forward to viewing Mars with the sphere eyepieces when it reappears. The was something special there.


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#49 SteveC

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Posted 01 June 2020 - 11:46 AM

Stevep,

 

Sorry for my part of in hijacking your thread. There were some comments I took personally.  I'm done.


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#50 stevep

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Posted 01 June 2020 - 02:03 PM

Does the catalogue have prices for Steinheil's orthos and Kellners?

 

What year was the catalogue produced?

Hi,

Catalogue is dated 1907 and yes it contains prices

link:   www.sil.si.edu/DigitalCollections/trade-literature/scientific-instruments/CF/SIsingle-record.cfm?AuthorizedCompany=C.A. Steinheil Söhne




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