General question about lighting - Pseudo Koehler
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General question about lighting - Pseudo Koehler
Hi All,
So I see people talking about pseudo Koehler. What does it mean? Does it mean collector lens without the iris?
Thanks
So I see people talking about pseudo Koehler. What does it mean? Does it mean collector lens without the iris?
Thanks
Re: General question about lighting - Pseudo Koehler
I don't know what pseudo koehler is, but modified Koehler usually involves a frosted lens just after the bulb. You get the even illumination and still get the rest of koehler (field iris, etc).
Re: General question about lighting - Pseudo Koehler
Just semantics, but I would consider pseudo-Koehler to be any fixed system for providing a reasonable facsimile of Koehler illumination for most purposes; so yes, generally a lens but no adjustable field diaphragm.
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Re: General question about lighting - Pseudo Koehler
I put an iris diaphragm centered directly on top of the illuminator and I get results similar to Koehler lighting. If there is very short distance between illuminator and condenser it won't work. It's a trial and error thing, but when it works it does a fair job.
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Re: General question about lighting - Pseudo Koehler
Thanks all. I think it is indeed frosted glass + collector without field diaphragm.
I found a nice video on the subject that helped me on the matter.
I found a nice video on the subject that helped me on the matter.
Re: General question about lighting - Pseudo Koehler
I can tell you that "pseudo-Koehler" illumination is not a misnomer as I almost fell victim to buying a scope that was not "full" Koehler but rather "simple" Koehler. The fact that some scopes are advertised as "full" Koehler indicates that some scopes are less than "Koehler." If they are < Koehler they are not Koehler.
Any tutorials that you find--and sorry I can't quote one at this moment-- tell you that what you need for bona fide Koehler illumination setup are three things:
1. A condenser lens that you can move in the Z direction,
2. Two condenser lens centering screws,
3. A field lens diaphragm.
If you have those components, you have the capacity for Koehler illumination. If you do not have those components, you do not have Koehler illumination.
Any tutorials that you find--and sorry I can't quote one at this moment-- tell you that what you need for bona fide Koehler illumination setup are three things:
1. A condenser lens that you can move in the Z direction,
2. Two condenser lens centering screws,
3. A field lens diaphragm.
If you have those components, you have the capacity for Koehler illumination. If you do not have those components, you do not have Koehler illumination.
Nikon AlphaPhot 2 < Zeiss Primostar 3, Full Köhler; Axiocam 208 Color < UHD LG
Aller Anfang ist schwer.
Aller Anfang ist schwer.
Re: General question about lighting - Pseudo Koehler
Another step in completing the Koehler illumination setup is pulling one ocular, looking down the eyetube, and adjusting the Abbe condenser aperture. This can be more precisely accomplished with a centering telescope, so you could add that as an optional feature.linuxusr wrote: ↑Wed Nov 03, 2021 10:07 pmI can tell you that "pseudo-Koehler" illumination is not a misnomer as I almost fell victim to buying a scope that was not "full" Koehler but rather "simple" Koehler. The fact that some scopes are advertised as "full" Koehler indicates that some scopes are less than "Koehler." If they are < Koehler they are not Koehler.
Any tutorials that you find--and sorry I can't quote one at this moment-- tell you that what you need for bona fide Koehler illumination setup are three things:
1. A condenser lens that you can move in the Z direction,
2. Two condenser lens centering screws,
3. A field lens diaphragm.
If you have those components, you have the capacity for Koehler illumination. If you do not have those components, you do not have Koehler illumination.
Nikon AlphaPhot 2 < Zeiss Primostar 3, Full Köhler; Axiocam 208 Color < UHD LG
Aller Anfang ist schwer.
Aller Anfang ist schwer.