Test Slides - Suggestions?

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J_WISC
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Test Slides - Suggestions?

#1 Post by J_WISC » Thu Feb 16, 2023 1:58 am

Hello.

Can someone recommend subjects, samples, test slides for evaluating eyepieces and objectives? I should have asked this long ago.

Just simple illumination. Is there something I could have on hand for quick prep of a slide? Or prepared slides I could purchase?

(I have a box of low-cost botany slides, but just realized they’re a bit sketchy and it’s hard tell if there’s a lens problem or a sample problem.)

Thank you for your time and patience and help.

PeteM
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Re: Test Slides - Suggestions?

#2 Post by PeteM » Thu Feb 16, 2023 2:05 am

A cheap micrometer slide works well to see planarity and chromatic aberrations.

Hobbyst46
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Re: Test Slides - Suggestions?

#3 Post by Hobbyst46 » Thu Feb 16, 2023 9:36 am

A dry blood smear slide can perhaps be gotten free from a clinical lab. It needs no coverslip and can serve for general impression, though not a substitute for the stage micrometer.

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blekenbleu
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Re: Test Slides - Suggestions?

#4 Post by blekenbleu » Thu Feb 16, 2023 10:11 am

Depending on your applications, micrometer slides with and without coverslips are wanted.
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apochronaut
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Re: Test Slides - Suggestions?

#5 Post by apochronaut » Thu Feb 16, 2023 10:50 am

Pete's suggestion gets you started but micrometers aren't that useful in evaluating contrast, resolution or spherical aberration in many cases. It would be useful to purchase a physical micrometer or caliper too, to measure both the slide itself and with care the slide, sample and cover amalgam of any prepared slides you encounter. . Thus you can deduce the sample/cover combined thickness and that should help you sort slides in order to stay within an objective's tolerance. Without being within that framework, you cannot evaluate how the system is performing during normal use with prepared slides because prepared slides are not very uniform.
The ideal coverslip/sample thickness changed very slightly over the years at Spencer, whose system you are mostly using. Early objectives were corrected for .18mm but there was a change to .17 at some point, probably with the change to infinity correction, in line with more general international standards.
Stained slides have limited value for evaluation without the experience of viewing many good similar ones, because they are designed to highlight certain festures and mask optical imperfections.
A thin smear of cheek epithelium from a swab and a small drop of water, then covered with a measured coverslip and gently pressed flat with the other end of the swab gives a fairly repeatable subject with low contrast that provides numerous challenges for optics. Those really thin onion membranes one encounters between layers,treated the same way, are about as good for low to medium magnification objectives.
Colourless is good. A thin smear of yogourt, or leave a tablespoon of milk out in a small container for a couple of days. Yeast if you have it or the brine from anything fermented and unfiltered, pickles ( not vinegar type), kim chee, Those are easily available unpigmented subjects with fairly repeatable transparent structures.
Always use measured coverslips, smears or account for the sample thickness if possible. Using an easily obtainable, easily repeatable subject that is available winter or summer is the key. You will become familiar with the sample, making the evaluation of the optics easier over time.
Obviously a good diatom slide with known standard species is ideal but the above choices are a little easier and cheaper to obtain.

Some subjects will dry out easily. There is a technique called "drawing under the cover slip" which is easy to do and preserves the subject for longer periods.

Using a small pipette or dropper, let a drop of your sample in under the cover of the sample beginning to dry while at the same time absorbing the sample with a wick of some kind on the other side. The liquid will be drawn under the cover and the cover can be settled adequately using such a technique. It is good for most subjefts that are homogeneous or emulsified. For structured subjects, use water. It takes a small amount of practice but few tools and low expertise.

Alternately, sealing the edges of the cover can be done but for routine evaluation using a known aqueous subject, drawing under the cover slip is fast, requires limited cleanup and the glass can be easily cleaned and reused if care is taken.

TonyT
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Re: Test Slides - Suggestions?

#6 Post by TonyT » Thu Feb 16, 2023 1:14 pm

New Brunswick
Canada

dtsh
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Re: Test Slides - Suggestions?

#7 Post by dtsh » Thu Feb 16, 2023 3:23 pm

I do as PeteM mentioned and use a stage micrometer for some tests, then I switch to mosquito wings and a diatom test slide I have. I usually end up looking at a variety of fly wings, but much of that is because I just find them interesting at such scales.
I'm not going to claim I really know what I'm doing, but I feel I get reasonable results. The diatom test slide I think is handy because there are a lot of structures and detail that will be a challenge for any light microscope. The mosquito wing is similar, perhaps a little less detail at the extreme range, but they're usually plentiful and available to just about everyone.

BramHuntingNematodes
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Re: Test Slides - Suggestions?

#8 Post by BramHuntingNematodes » Thu Feb 16, 2023 3:57 pm

Butterfly scales are good in line with the mosquito wing
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