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iangreenhalgh1
Joined: 18 Mar 2011 Posts: 15679
Expire: 2014-01-07
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Posted: Mon Oct 31, 2011 1:16 am Post subject: Unusual Cooke lens - Microscope? |
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iangreenhalgh1 wrote:
Hi folks
I bought an unusual lens that I suspect may be for a microscope, the only markings on it are:
Cooke 40949 D.G.
It has a thread mount approximately twice the diameter of a normal RMS microscope thread mount and is very squat, only a third as tall as it is wide.
Looking into the lens from the front all I can see is black, looking into it from the rear, it has a silvered surface like a blob of mercury and just reflects my own face back at me.
Anyone ever seen anything like this before? Google finds nothing. _________________ I don't care who designed it, who made it or what country it comes from - I just enjoy using it! |
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adent
Joined: 06 Oct 2011 Posts: 304 Location: United States
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Posted: Mon Oct 31, 2011 1:21 am Post subject: |
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adent wrote:
I have no knowledge about this subject matter, I suspect however that the people that do will ask for a picture of the lens in question. |
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Mos6502
Joined: 20 Jun 2011 Posts: 960 Location: Austin
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Posted: Mon Oct 31, 2011 1:30 am Post subject: |
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Mos6502 wrote:
Does light pass through it?
Also yes a picture would be interesting. |
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iangreenhalgh1
Joined: 18 Mar 2011 Posts: 15679
Expire: 2014-01-07
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Posted: Mon Oct 31, 2011 1:34 am Post subject: |
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iangreenhalgh1 wrote:
No light passes through the centre but there is a thin transparent region around the edges of the silvery reflective spot.
_________________ I don't care who designed it, who made it or what country it comes from - I just enjoy using it! |
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SXR_Mark
Joined: 12 Jun 2010 Posts: 506 Location: England
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Posted: Mon Oct 31, 2011 8:07 am Post subject: |
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SXR_Mark wrote:
It could be a Schwarzschild objective.
http://spie.org/x34462.xml _________________ Olympus OM-D E-M1 for everything |
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Sevo
Joined: 22 Aug 2008 Posts: 1189 Location: Frankfurt, Germany
Expire: 2012-12-03
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Posted: Mon Oct 31, 2011 9:09 am Post subject: |
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Sevo wrote:
It is far more likely to be a dark field lens. _________________ Sevo |
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kds315*
Joined: 12 Mar 2008 Posts: 16643 Location: Weinheim, Germany
Expire: 2021-03-09
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Posted: Mon Oct 31, 2011 11:48 am Post subject: |
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kds315* wrote:
Certainly not a Schwarzschild reflective objective, as it is way too small - Cooke reflective objectives look like that:
I agree with sevo that it might be a Darkfield objective, as the center rays are blocked out. _________________ Klaus - Admin
"S'il vient a point, me souviendra" [Thomas Bohier (1460-1523)]
http://www.macrolenses.de for macro and special lens info
http://www.pbase.com/kds315/uv_photos for UV Images and lens/filter info
https://www.flickr.com/photos/kds315/albums my albums using various lenses
http://photographyoftheinvisibleworld.blogspot.com/ my UV BLOG
http://www.travelmeetsfood.com/blog Food + Travel BLOG
https://galeriafotografia.com Architecture + Drone photography
Currently most FAV lens(es):
X80QF f3.2/80mm
Hypergon f11/26mm
ELCAN UV f5.6/52mm
Zeiss UV-Planar f4/60mm
Zeiss UV-Planar f2/62mm
Lomo Уфар-12 f2.5/41mm
Lomo Зуфар-2 f4.0/350mm
Lomo ZIKAR-1A f1.2/100mm
Nikon UV Nikkor f4.5/105mm
Zeiss UV-Sonnar f4.3/105mm
CERCO UV-VIS-NIR f1.8/45mm
CERCO UV-VIS-NIR f4.1/94mm
CERCO UV-VIS-NIR f2.8/100mm
Steinheil Quarzobjektiv f1.8/50mm
Pentax Quartz Takumar f3.5/85mm
Carl Zeiss Jena UV-Objektiv f4/60mm
NYE OPTICAL Lyman-Alpha II f1.1/90mm
NYE OPTICAL Lyman-Alpha I f2.8/200mm
COASTAL OPTICS f4/60mm UV-VIS-IR Apo
COASTAL OPTICS f4.5/105mm UV-Micro-Apo
Pentax Ultra-Achromatic Takumar f4.5/85mm
Pentax Ultra-Achromatic Takumar f5.6/300mm
Rodenstock UV-Rodagon f5.6/60mm + 105mm + 150mm
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iangreenhalgh1
Joined: 18 Mar 2011 Posts: 15679
Expire: 2014-01-07
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Posted: Mon Oct 31, 2011 1:08 pm Post subject: |
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iangreenhalgh1 wrote:
Yes, it seems to me that the D.G. on the lens stands for 'Dark Ground' so it will indeed by a darkfield lens.
I wonder what magnification it is and if it will be of any use for macro work? _________________ I don't care who designed it, who made it or what country it comes from - I just enjoy using it! |
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kds315*
Joined: 12 Mar 2008 Posts: 16643 Location: Weinheim, Germany
Expire: 2021-03-09
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Posted: Mon Oct 31, 2011 4:06 pm Post subject: |
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kds315* wrote:
Works only for transmitted light using a special condensor system. _________________ Klaus - Admin
"S'il vient a point, me souviendra" [Thomas Bohier (1460-1523)]
http://www.macrolenses.de for macro and special lens info
http://www.pbase.com/kds315/uv_photos for UV Images and lens/filter info
https://www.flickr.com/photos/kds315/albums my albums using various lenses
http://photographyoftheinvisibleworld.blogspot.com/ my UV BLOG
http://www.travelmeetsfood.com/blog Food + Travel BLOG
https://galeriafotografia.com Architecture + Drone photography
Currently most FAV lens(es):
X80QF f3.2/80mm
Hypergon f11/26mm
ELCAN UV f5.6/52mm
Zeiss UV-Planar f4/60mm
Zeiss UV-Planar f2/62mm
Lomo Уфар-12 f2.5/41mm
Lomo Зуфар-2 f4.0/350mm
Lomo ZIKAR-1A f1.2/100mm
Nikon UV Nikkor f4.5/105mm
Zeiss UV-Sonnar f4.3/105mm
CERCO UV-VIS-NIR f1.8/45mm
CERCO UV-VIS-NIR f4.1/94mm
CERCO UV-VIS-NIR f2.8/100mm
Steinheil Quarzobjektiv f1.8/50mm
Pentax Quartz Takumar f3.5/85mm
Carl Zeiss Jena UV-Objektiv f4/60mm
NYE OPTICAL Lyman-Alpha II f1.1/90mm
NYE OPTICAL Lyman-Alpha I f2.8/200mm
COASTAL OPTICS f4/60mm UV-VIS-IR Apo
COASTAL OPTICS f4.5/105mm UV-Micro-Apo
Pentax Ultra-Achromatic Takumar f4.5/85mm
Pentax Ultra-Achromatic Takumar f5.6/300mm
Rodenstock UV-Rodagon f5.6/60mm + 105mm + 150mm
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iangreenhalgh1
Joined: 18 Mar 2011 Posts: 15679
Expire: 2014-01-07
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Posted: Mon Oct 31, 2011 4:10 pm Post subject: |
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iangreenhalgh1 wrote:
Ah well, it was one of a job lot of Cooke microscope lenses I bought very cheap, the others will prove useful. _________________ I don't care who designed it, who made it or what country it comes from - I just enjoy using it! |
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DSG
Joined: 04 Mar 2007 Posts: 544 Location: London, UK.
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Posted: Mon Oct 31, 2011 9:13 pm Post subject: |
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DSG wrote:
But what does a dark field or "dark ground" lens actually do/what is its purpose? Going by the description given by the OP, I assumed it was used in a telescope to block out the suns disc so that the suns corona could be observed safely by eye but that cant be right can it? |
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danfromm
Joined: 04 Sep 2011 Posts: 585
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Posted: Mon Oct 31, 2011 11:43 pm Post subject: |
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danfromm wrote:
DSG wrote: |
But what does a dark field or "dark ground" lens actually do/what is its purpose? Going by the description given by the OP, I assumed it was used in a telescope to block out the suns disc so that the suns corona could be observed safely by eye but that cant be right can it? |
http://en.wikipedia.org/wiki/Dark_field_microscopy |
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