Snagged Some More Objectives for the 4 Series Apostar

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desertrat
Posts: 243
Joined: Thu Apr 05, 2018 1:06 am
Location: Idaho

Snagged Some More Objectives for the 4 Series Apostar

#1 Post by desertrat » Sun Dec 16, 2018 1:25 am

An early Christmas present to myself. I probably paid too much for them, but these don't seem to turn up very often on the 'Bay, and I was regretting not buying the 90X Apo that sold a while back.

This seller has a good feedback rating, and received positive feedback for recent sales of objectives and microscope parts.
3_AO_Apos.JPG
3_AO_Apos.JPG (34.42 KiB) Viewed 3022 times
Adding the 20x from the set I already have, I now have a set of 4 of these gold plated apochromats.
Apos_on_nosepiece.JPG
Apos_on_nosepiece.JPG (83.17 KiB) Viewed 3022 times
I really only wanted a 90X to replace the one in my existing set, because it has real bad delamination in the upper group and gives a very poor image, not usable. But my existing 43X apo was also not in perfect condition. There is a touch of delamination around the very outer edge of the upper group, but also some localized delamination near the edge of the group just above the bottom plano convex element. And although localized to one spot, it extended in a ways toward the center. Actually, it looked kind of bad looking at it with a magnifier toward the light, but image quality is excellent as far as I can tell. My existing 10X and 20X apochromats are in perfect condition, as far as I can tell.

These lenses are from an older series, with serial numbers beginning with the letter B. My existing set have numbers beginning with the letter C.

One thing interesting is these older lenses are almost a whole millimeter longer than their counterparts in my existing set. I found this out right away when using my existing 20X objective with these new (to me) ones. Comparing them side by side it's easy to see.

These new to me lenses perform great, especially the 90X. It is sharper than any of my other oil immersion achromats, and the antique fluorite objective as well. I was kind of surprised, though, at the curvature of field, as great as my achromats, and slightly greater then the old fluorite, but sharper.

Not complaining though, it was made before plan objectives came on the market (as far as I know), and looking at the sharp image with the slight fuzziness seen through the achromats removed is very satisfying.
Rick

A/O 10 Series Microstar
A/O 4 Series Microstar
A/O 4 Series Phasestar
A/O 4 Series Apostar
A/O Cycloptic Stereo
Several old monocular scopes in more or less decrepit but usable condition

billbillt
Posts: 2883
Joined: Mon Nov 10, 2014 10:01 pm

Re: Snagged Some More Objectives for the 4 Series Apostar

#2 Post by billbillt » Sun Dec 16, 2018 5:46 am

Very interesting collection.. Could you post photos of subjects taken thru these?..

BillT

desertrat
Posts: 243
Joined: Thu Apr 05, 2018 1:06 am
Location: Idaho

Re: Snagged Some More Objectives for the 4 Series Apostar

#3 Post by desertrat » Sun Dec 16, 2018 8:47 pm

Thanks, Bill. I'll prepare some comparison images in the next few days, but my current image capture equipment just isn't capable of recording the finest detail of the beautifully sharp, crisp images these objectives produce.

Then again, it's probably just as well I don't have access to modern highly corrected microscope optics to compare, as I might become a bit disappointed with my nearly antique microscopes and optics.
Rick

A/O 10 Series Microstar
A/O 4 Series Microstar
A/O 4 Series Phasestar
A/O 4 Series Apostar
A/O Cycloptic Stereo
Several old monocular scopes in more or less decrepit but usable condition

apochronaut
Posts: 2722
Joined: Fri May 15, 2015 12:15 am

Re: Snagged Some More Objectives for the 4 Series Apostar

#4 Post by apochronaut » Sun Dec 16, 2018 9:28 pm

desertrat wrote:
Then again, it's probably just as well I don't have access to modern highly corrected microscope optics to compare, as I might become a bit disappointed with my nearly antique microscopes and optics.
Any obvious differences between the gp objectives and the late 50's brushed chrome edition? I have never had the opportunity to compare them but the latter are coated , are they not?

desertrat
Posts: 243
Joined: Thu Apr 05, 2018 1:06 am
Location: Idaho

Re: Snagged Some More Objectives for the 4 Series Apostar

#5 Post by desertrat » Sun Dec 16, 2018 10:07 pm

apochronaut wrote:
desertrat wrote:
Then again, it's probably just as well I don't have access to modern highly corrected microscope optics to compare, as I might become a bit disappointed with my nearly antique microscopes and optics.
Any obvious differences between the gp objectives and the late 50's brushed chrome edition? I have never had the opportunity to compare them but the latter are coated , are they not?
Both sets of apos are coated. The 10X objectives are the only ones easy to see reflected light sources from their elements, and both sets have different color casts from a reflected incandenscent light bulb from the different lens surfaces. The higher power objectives are more difficult, but I can see faint differences in reflected colors from the lens surfaces using a miniature LED flashlight shined into the barrels.

Using my antique brass objectives for comparison, there are no differences in color casts from reflections of an incandescent light bulb or flashlight LED from the different lens surfaces, as would be expected from an uncoated lens. The color cast of the reflections are identical to the color cast of the bare bulb or LED.

Performance is identical, as far as I can tell, between the two sets of objectives. I'm guessing the plated objectives were manufactured after WW2, when lens coatings became common, but before the change to the brushed chrome objective barrels.
Rick

A/O 10 Series Microstar
A/O 4 Series Microstar
A/O 4 Series Phasestar
A/O 4 Series Apostar
A/O Cycloptic Stereo
Several old monocular scopes in more or less decrepit but usable condition

apochronaut
Posts: 2722
Joined: Fri May 15, 2015 12:15 am

Re: Snagged Some More Objectives for the 4 Series Apostar

#6 Post by apochronaut » Mon Dec 17, 2018 2:48 pm

In the 1961 catalogue for the series 2/4, as was also the case in 1955, they list magnesium fluoride "americote" coatings as standard for all of the essential glass surfaces of the optics. Prior to that it was an option since around 1950, with coated catalogue #'s being prefixed by a C. In the May 1961 catalogue, they still picture the apochromat objectives with the gold plating, so the brushed chrome ones must have been quite late in the production of the 2/4, because the series 10 arrived very shortly after, although there was probably a period of production overlap between the 160mm series' and the oo series'. There was a pair of infinity corrected apos : a 10x .30 and a 43x .85, which look physically very similar to those brushed chrome 160mm ones. I don't know their time of production but they were quite early in the series 10/20 development and the coating on those is different from the coatings on any 160mm objectives I have, including apochromats. At some point they also dropped reference to Americote, so the coating formulation most likely changed in the early 60's.

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