New Purchase Bestscope Model BS-2080 Chinese vs Big 5

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Nance
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Re: New Purchase Bestscope Model BS-2080 Chinese vs Big 5

#61 Post by Nance » Fri Feb 02, 2018 4:05 pm

Thanks for The Diatom Shop lead charlie g... trying to justify buying an older stereo microscope - but now I am wondering if a set of apochromatic objectives might be a smarter priority. awaiting the sage advice of Einman. (ortho-illuminator 'out for delivery' today btw, thanks again).

einman
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Re: New Purchase Bestscope Model BS-2080 Chinese vs Big 5

#62 Post by einman » Sat Feb 03, 2018 5:07 am

My comments in reference to APO objectives perhaps has been a bit misunderstood. Whenever I make a purchase I am evaluating the ROI, the return on investment. Granted an APO objective is without a doubt superior, but does it justify the price differential? That is a subjective question dependent on many variables, one of which is your ability to afford such an objective, the other being your ability to to perceive the difference. It also depends somewhat on the subject matter and your tolerance for precision. What do I mean by that? Well most Planapo objectives have very small working distances. In some cases that WD is less than the thickness of a common cover-glass. Thus in order to obtain the full capability they are equipped with a collar to adjust for variances in cverglass thickness. If you do not have the patience to insure your cover-glass thickness is optimal, or the collar is properly adjusted for the cover-glass, than the image seen through that very expensive planapo objective may not be any better than the planachromat which came with your microscope.

For example a typical planachromat objective 40X/0.65 na has a typical WD of about 0.56 mm compared to the planapo 40x/0.95 na at about 0.15 mm or less. A 0.02 mm deviation in coverslip thickness with the planapo can result in a 71% performance reduction per Nikon. Whereas that same coverslip deviation of 0.02 mm results in less than a 2% reduction in performance of the planachromat 40X/0.65. So.. If you fail to make the correct adjustments for that planapo you could easily have a significantly poorer image than you had with your standard planachromat.

It is noteworthy to mention there are individuals on this forum adept at squeezing the maximum performance out of a planachromat to the point of challenging many apochromats of the same magnification but higher na.

Unless you are an individual that is willing to be "precise" and meticulous in your microscopy, investing in planapos is money best spent elsewhere.

A good compromise are Planfluor objectives. For example a Nikon CFI planfluor 40x/0.75 objective has a working distance of 0.72mm or about the thickness of 4 cover slips. Compare that to a CFI planapo 40x/0.95 which has a working distance of 0.14 mm, less than the average thickness of s single coverslip. If you do not make the proper corrections for the planapo and have 0.02 mm deviation in the coverslip setting you could potentially see a 71% reduction in resolution. So the NA would essentially be equivalent to that of a planachromat. Using that same coverslip with the Planfluor would have significantly less effect so it would perform better for most hobbyists at a lower price.

I believe this is one reason both Leitz and American Optical chose to produce planapos with an na of 0.8, the max na recommended without a collar. So under most circumstances and given many individuals propensity to be less "meticulous" in their adjustments those objectives performed superbly if not superior to most of their competition with higher na's. Not to mention the reduction in complexity resulted in lower manufacturing costs.

This is probably even more pertinent if the hobbyist spends their time looking at cheap prepared slides. In some situations even the collar on a planapo can not compensate for the thickness of the coverslip or the depth of the specimen on the slide etc. In that case the planapo is a complete waste.

Precision of equipment aside, if you have problems with tired eyes, wear corrective lenses or other eye defects than you have to decide if the investment in a planapo is worth it as well. I have found that my eyeglasses can result in inferior images unless I take special care in cleaning them and making sure they are properly situated on my face when using the scope. You can spend a ton of money on your scope, objectives and eyepieces only to have the image affected by your eyeglasses. It is for this reason when comparing microscopes or objectives I tend to discuss relative differences, as talking in the absolute introduces more error. Alternatively I like to have another individual nearby to corroborate.

So ask yourself what type of hobbyist are you? Then purchase the objectives best suited to your type of work.
Last edited by einman on Sat Feb 03, 2018 3:30 pm, edited 1 time in total.

Hobbyst46
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Re: New Purchase Bestscope Model BS-2080 Chinese vs Big 5

#63 Post by Hobbyst46 » Sat Feb 03, 2018 1:27 pm

Thanks a lot, Charlie G, for pointing out the Italian "Diatom Shop"!.

A very attractive site it is. I enjoyed reading there. Prices are somewhat high for me, but probably reflect the manual labor behind each slide.

I find it interesting that they developed their own high refractive index mounting media, based on using "Aroclor" and other hazardous chemicals. They have the required safety facilities. But I wonder why, given the declared excellence of other commercial and established proprietary mountants, would any business-minded laboratory like the Diatom Shop want to allocate resources to invent or develop their own unique mounting media ? is it because they plan to sell them freely some day? who knows...
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

einman
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Re: New Purchase Bestscope Model BS-2080 Chinese vs Big 5

#64 Post by einman » Sat Feb 03, 2018 3:29 pm

Hobbyst46 wrote:Thanks a lot, Charlie G, for pointing out the Italian "Diatom Shop"!.

A very attractive site it is. I enjoyed reading there. Prices are somewhat high for me, but probably reflect the manual labor behind each slide.

I find it interesting that they developed their own high refractive index mounting media, based on using "Aroclor" and other hazardous chemicals. They have the required safety facilities. But I wonder why, given the declared excellence of other commercial and established proprietary mountants, would any business-minded laboratory like the Diatom Shop want to allocate resources to invent or develop their own unique mounting media ? is it because they plan to sell them freely some day? who knows...
I have not had the chance to check out the site. Is their mounting media actually "unique" or perhaps simply re-labeling an existing medium? I generally look for patents etc to signal if something is actually unique. Although the lack of a patent does not mean it is not unique, as you can have "trade secrets" which you do not patent.

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Crater Eddie
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Re: New Purchase Bestscope Model BS-2080 Chinese vs Big 5

#65 Post by Crater Eddie » Sat Feb 03, 2018 10:03 pm

einman wrote:My comments in reference to APO objectives perhaps has been a bit misunderstood...
Thanks for this, very interesting points.
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SunshineLW
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Re: New Purchase Bestscope Model BS-2080 Chinese vs Big 5

#66 Post by SunshineLW » Sun Mar 04, 2018 10:48 am

Thank you for sharing! This is very useful information, especially to beginner hobbyists!

MicroBob
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Re: New Purchase Bestscope Model BS-2080 Chinese vs Big 5

#67 Post by MicroBob » Mon Mar 05, 2018 12:42 pm

There has been spent so much time on developing high r.i. diatom mountants that my first guess would always be that any new mountant is either not first class or known before. But even when you have the best diatom mountants and diatom material, it is still difficult enough to make a great slide from it.
Aroclor hat been out of production since about 1980 but it has a good name as a diatom mountant. What I don't like about it is that it continues to evaporate for a long time and the coverslips draw air.
Interesting to read is that he uses Dammar resin for which I found an r.i. of 1.515 -1.539.

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Re: New Purchase Bestscope Model BS-2080 Chinese vs Big 5

#68 Post by Hobbyst46 » Mon Mar 05, 2018 2:51 pm

einman wrote:My comments in reference to APO objectives perhaps has been a bit misunderstood. Whenever I make a purchase I am evaluating the ROI, the return on investment. Granted an APO objective is without a doubt superior, but does it justify the price differential? ...planachromat objective 40X/0.65 na has a typical WD of about 0.56 mm compared to the planapo 40x/0.95 na at about 0.15 mm or less. A 0.02 mm deviation in coverslip thickness with the planapo can result in a 71% performance reduction per Nikon. Whereas that same coverslip deviation of 0.02 mm results in less than a 2% reduction in performance of the planachromat 40X/0.65.
So......
...........
Using that same coverslip with the Planfluor would have significantly less effect so it would perform better for most hobbyists at a lower price.
Thanks a lot for these reminders. Very important issue. It is so easy to forget about coverslip thickness, and to check it since they are somewhat fragile....
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

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