Do Chinese noname Plan objectives need compensating eyepieces?

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jjtr1
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Do Chinese noname Plan objectives need compensating eyepieces?

#1 Post by jjtr1 » Thu May 12, 2022 10:17 am

Hello,
I'd like to ask about noname Chinese plan finite objectives that are available new on eBay. In general, do they require compensating eyepieces, just like most older finite plan objectives from major brands? I understand there is a lot of these new noname objectives and nothing can be said in general. So I'm looking for personal experience with some of them.

The backstory is that I bought a Nikon Alphaphot-2 from the 1990s very cheaply for about $ 75 (not in US), equipped with Nikon CF 40x and 100x achromats. Nikon CF is an exception among finite systems in that it doesn't require compensating eyepieces. I'd like to add the missing 10x and 20x, without the need to change eyepieces. Used Nikon CF objectives are too expensive, so I'm looking at new chinese objectives, preferably plan. On top of that, I have pair of very very comfortable orthoscopic eyepieces (non-compensating), which I'd like to use (scope came with only one Nikon CF eyepiece).

My scope also included a Zeiss Jena 10x planachromat, so I know how bad lateral color is when an objective doesn't receive the compensation it needs.

Thanks for your suggestions!

PeteM
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Re: Do Chinese noname Plan objectives need compensating eyepieces?

#2 Post by PeteM » Thu May 12, 2022 4:13 pm

I haven't done either an exhaustive study or a detailed look, but my impression is, yes, they are neutral.

More definitely so in the plan achromat and plan fluor infinity offerings, where I've found different reference tube lengths (180, 200), and somewhat lower quality, parfocality, and parcentering than their Olympus and Nikon equivalents - but generally good values.

My experience is that if you're patient you find used Nikon 10x and (more patience) 20x finite E Plan (CF) objectives for about the same cost of new generics.

apochronaut
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Re: Do Chinese noname Plan objectives need compensating eyepieces?

#3 Post by apochronaut » Fri May 13, 2022 1:21 am

jjtr1 wrote:
Thu May 12, 2022 10:17 am

My scope also included a Zeiss Jena 10x planachromat, so I know how bad lateral color is when an objective doesn't receive the compensation it needs.
I may be wrong but I think Jena was still using an achromat : correcting eyepiece and apochromat : compensating eyepiece system. Systems adopting a compensating condition for both arrived on a staggered basis mfg. by mfg. from the 60's onward. AO were the first or at least one of the first to harmonize achromat and apochromat requirements but used primarily correcting eyepieces for both in the 34mm parfocal system, making a further adjustment in the telan lens. They switched to a slightly compensating system for the 45mm parfocal system. B & L also harmonized early but with a slightly compensating system for the Flat Field microscopes and on the surface the degree of compensation between those and the AO/Reichert 45mm system seems similar but in use, they employ different levels of field curvature correction in the eyepiece. Close for ca, though.

With the Chinese 160mm objectives they seem to fall into 2 camps. Nikon or Olympus types, at least in style but I would be suspicious whether each might actually use correcting eyepieces, whereas Nikon are closer to neutral. Then there is the issue as above with planarity. I would be surprised if the planarity calculations were identical.If you can get your hands on an eyepiece used in one of the Chinese systems that will tell you.

Just as an aside, I use a Nikon 160mm CF objective in a system along with Reichert (Austria) infinity objectives, both in a system they were not designed for, using fairly compensating eyepieces designed for a stereoscope. The ca corrections work out very well. The reason I do this is due to the glycerin immersion capacity in DF of both the Nikon CF 100X and the Reichert 63X . This does mean that the Reichert objectives and the Nikon CF have an equivalent native need for correction/compensation but there is a slight bit of not particularly annoying curvature with the CF objective and it's magnification is + 10%.

Chas
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Re: Do Chinese noname Plan objectives need compensating eyepieces?

#4 Post by Chas » Fri May 13, 2022 9:37 am

EDIT : It was me, not them, so they will not be languishing in their pots any more :-)

I purchased some (UK) and to be honest I haven't got on well with them.
I havent found an eyepiece to correct them.
..they languish unused/unusable in their pots :-(
Last edited by Chas on Mon May 16, 2022 6:20 am, edited 1 time in total.

Phill Brown
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Re: Do Chinese noname Plan objectives need compensating eyepieces?

#5 Post by Phill Brown » Fri May 13, 2022 1:54 pm

Chas wrote:
Fri May 13, 2022 9:37 am
I purchased some (UK) and to be honest I haven't got on well with them.
I havent found an eyepiece to correct them.
..they languish unused/unusable in their pots :-(
Put them in bags and sell the pots? sorry,just a thought if they are nasty to look through.I never seem to have enough pots but bags,oh yes.

jjtr1
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Re: Do Chinese noname Plan objectives need compensating eyepieces?

#6 Post by jjtr1 » Fri May 13, 2022 4:12 pm

apochronaut wrote:
Fri May 13, 2022 1:21 am
I may be wrong but I think Jena was still using an achromat : correcting eyepiece and apochromat : compensating eyepiece system. Systems adopting a compensating condition for both arrived on a staggered basis mfg. by mfg. from the 60's onward. AO were the first or at least one of the first to harmonize achromat and apochromat requirements but used primarily correcting eyepieces for both in the 34mm parfocal system, making a further adjustment in the telan lens. They switched to a slightly compensating system for the 45mm parfocal system. B & L also harmonized early but with a slightly compensating system for the Flat Field microscopes and on the surface the degree of compensation between those and the AO/Reichert 45mm system seems similar but in use, they employ different levels of field curvature correction in the eyepiece. Close for ca, though.

With the Chinese 160mm objectives they seem to fall into 2 camps. Nikon or Olympus types, at least in style but I would be suspicious whether each might actually use correcting eyepieces, whereas Nikon are closer to neutral.
Thank you for your answer, I'm always looking to learn new things. What is a correcting eyepiece, as opposed to a compensating eyepiece? I assume "correcting" means having a curvature of field of the opposite sign to the objective's, while "compensating" means chromatic difference of magnification of the opposite sign to the objective's?

With regard to the Zeiss Jena 10x planachromat, I can say the lateral color is gone when used with the lone Zeiss Jena 16x PK eyepiece I have (bought out of curiosity).

Chas
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Re: Do Chinese noname Plan objectives need compensating eyepieces?

#7 Post by Chas » Fri May 13, 2022 7:55 pm

I am begining to wonder if some of the issue I had with the plan objectives might be because I changed the light-source from low voltage incandescent to LED, at around the same time.
I will have to check.

UPDATE: It is most definitely something to do with changing my light source .... whether it was just the dramatic change in colour temperature of the light, or the positioning of it I am not sure.
Last edited by Chas on Mon May 16, 2022 6:17 am, edited 3 times in total.

Phill Brown
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Re: Do Chinese noname Plan objectives need compensating eyepieces?

#8 Post by Phill Brown » Sat May 14, 2022 7:54 am

Chas wrote:
Fri May 13, 2022 7:55 pm
I am begining to wonder if some of the issue I had with the plan objectives might be because I changed the light-source from low voltage incandescent to LED, at around the same time.
I will have to check.
[/quote
LED is fuzzy and nasty mostly which is why they need diffusing so much.
Just ask the field iris.
They can be good with flooding super wide FOV that isn't necessary but seems great at first.
Then everything has to be plan and the price of objectives goes up.
I do wonder who is driving sometimes.
Halogen apparently isn't green enough for citizen science so it's LED untill another technology replaces the obsolete DC diode.
Back when we had jumpers for goal posts the mirror used sunlight which can be diffused or not depending on the day.
It's worth checking out the old system to keep progress in perspective.
Just saying maybe vintage 160mm might have some life left in it yet.
Now,where did I leave my credit card.

Chas
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Re: Do Chinese noname Plan objectives need compensating eyepieces?

#9 Post by Chas » Sat May 14, 2022 8:15 am

....You mentioned a shortage of pots for storing objectives.
These aren't so bad at 40pence each:
self standing centrifuge tubes 50ml 640.jpg
self standing centrifuge tubes 50ml 640.jpg (25.45 KiB) Viewed 1544 times
They are cone-shaped at the bottom and so the the bottom glass of the objective is held 'up in the air'.
(& if you were really pushed for storage you could fit in two, back to back).

apochronaut
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Re: Do Chinese noname Plan objectives need compensating eyepieces?

#10 Post by apochronaut » Sun May 15, 2022 3:04 pm

jjtr1 wrote:
Fri May 13, 2022 4:12 pm
apochronaut wrote:
Fri May 13, 2022 1:21 am
I may be wrong but I think Jena was still using an achromat : correcting eyepiece and apochromat : compensating eyepiece system. Systems adopting a compensating condition for both arrived on a staggered basis mfg. by mfg. from the 60's onward. AO were the first or at least one of the first to harmonize achromat and apochromat requirements but used primarily correcting eyepieces for both in the 34mm parfocal system, making a further adjustment in the telan lens. They switched to a slightly compensating system for the 45mm parfocal system. B & L also harmonized early but with a slightly compensating system for the Flat Field microscopes and on the surface the degree of compensation between those and the AO/Reichert 45mm system seems similar but in use, they employ different levels of field curvature correction in the eyepiece. Close for ca, though.

With the Chinese 160mm objectives they seem to fall into 2 camps. Nikon or Olympus types, at least in style but I would be suspicious whether each might actually use correcting eyepieces, whereas Nikon are closer to neutral.
Thank you for your answer, I'm always looking to learn new things. What is a correcting eyepiece, as opposed to a compensating eyepiece? I assume "correcting" means having a curvature of field of the opposite sign to the objective's, while "compensating" means chromatic difference of magnification of the opposite sign to the objective's?

With regard to the Zeiss Jena 10x planachromat, I can say the lateral color is gone when used with the lone Zeiss Jena 16x PK eyepiece I have (bought out of curiosity).
The two terms : correction and compensation often get interchanged but in fact are on opposite sides of neutral. Up until around 1960 when exotic glass formulas allowed for a harmonization of achromat , fluorite and apochromat designs around a common eyepiece design, lens designers attempted to neutralize their achromat and fluorite objective's inadequacies with various correcting eyepieces. These were usually tried and true types such as Huygens, Ramsden, Kellner or Orthoscopic , often modified somewhat in ordered to improve planarity, such as in the Planoscopic eyepiece. At the same time, with apochromats, there was considerable effort made to bring those objectives to s state of complete correction for spherical aberration. This caused chromatic aberration to be over corrected in the objective, requiring the use of proprietary eyepieces marked as compensating, compens , comp. or other in order to bring the ca back to neutral.
Correcting eyepieces therefore were standard eyepieces, whereas compensating eyepieces were used with apochromats and sometimes as photo eyepieces, where adequately cropped ,with achromats.
PK or plancompensating are usually something different : compensating for imperfect planarity in the objective with the eyepiece/objective partnership necessary for full planarity. That usually includes correction for aberrations across the field as well. PK eyepieces are always proprietaty and dedigned to be used with a specific family of objectives.

In modern microscopes : all objective series are brought to the same levels of correction or overcorrection and a specific eyepiece design is required to harmonize with them. It is usually neutral to slightly compensationg.

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