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Old 11-17-2012, 09:54 PM   #11
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Originally Posted by ajdelange View Post
Yes, I saw those Amazon reviews. I'm still scratching my head. An oil immersion capability in a binocular scope for $165 is really unbelievable. You'll see what you'll see when you get it but you should be able to use it for counting in any case.
Yeah, anyone can sell you a lens and tell you to use immersion oil with it. The tricky part is actually producing a lens that will be diffraction limited when used with immersion oil and a coverslip. I'd pretty much guarantee that at this price the higher magnifications will have some massive aberrations (see the amazon review about 'Focus Issues' - sounds like significant spherical aberration). The fact that the listing won't tell you any of the lens specifications (other than magnification) is a bit worrisome too, but if all you want is cell counts, fuzzy blobs should be ok.

 
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Old 11-17-2012, 11:02 PM   #12
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Thanks for the input bdh

Do you have an idea what the markings on the objective may mean? This is what is written on them:
Plan 4/0.1 160/0.17
Plan 10/0.25 160/0.17
Plan 40/0.65 160/0.17
Plan 100/1.25 oil 160/0.17
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Old 11-17-2012, 11:22 PM   #13
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The first two numbers are, respectively, the magnification and the numerical aperture (n*sin(acceptance angle)) where n is the index of refraction of the air or oil. I think the second two may be, respectively, the focus distance and cover slip thickness. Not so sure here and don't know what the working distance is measured from or what units it's in.

 
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Old 11-17-2012, 11:59 PM   #14
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Quote:
Originally Posted by ajdelange View Post
The first two numbers are, respectively, the magnification and the numerical aperture (n*sin(acceptance angle) where n is the index of refraction of the air or oil. I think the second two may be, respectively, the focus distance and cover slip thickness. Not so sure here and don't know what the working distance is measured from or what units it's in.
the last number is indeed the cover slip thickness.
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Old 11-18-2012, 10:21 PM   #15
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Yeah, the values are:

Magnification, numerical aperture, tube length, and coverslip thickness. Of all of these, numerical aperture is probably the most important, since it directly limits the maximum possible resolution of the system.

The tube length describes how far behind the back aperture of the objective the image will be focused. Most modern microscopes use infinity corrected objectives (i.e. when you place the specimen at the working distance of the objective all of the light rays coming out the back aperture of the objective are parallel) since you can place other optics (such as color filters, polarizers, dichromatic mirrors, etc...) in the light path without changing the focal length of the system. The 160mm listed on these objectives was the 'old' standard that was used on microscopes up until the 1980s or so. The actual value isn't that important as long as you use the objective with a compatible microscope and don't try to add any intermediate optics to the system.

The 'Plan' listed on these objectives refers to a 'Planar' corrected objective, which means the objective has been corrected to have a flat field of focus across the entire plane in the field of view.

If these objectives really are what they're listed as, then this is a great deal. If you were to call up Olympia/Nikon/Zeiss and ask for their cheapest Planar 4X 0.1NA objective lens you'd probably be looking at a few hundred dollars already (for just the lens). To get the higher magnification and higher NA lenses the price would probably go into the thousands. So, that being said, I'm still pretty skeptical of these lenses, but I suppose it might be possible that this company can get objectives with a 160mm tube length for cheap since they're not used much anymore....

 
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Old 11-21-2012, 04:47 PM   #16
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Thank you everyone for your valuable information. I ended up getting the Binocular Amscope. Like everyone said, it's not an Olympus, but fine for counting cells. So far, I am pleasantly surprised by its capability. It has already saved a batch of beer! When doing cell counts on my S-03 slurry I saw an enormous number of small moving partials. They are approximately 1 micron in size which is about the limit of the resolution at 400x. The concentration of them is about twice that of the viable yeast cells. On other slurrys I didn't see that type of bacteria, so the S-03 is going down the sink instead of into my next brew.

For several pictures and more information about this scope see this blog post:
http://woodlandbrew.blogspot.com/201...icroscope.html
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Old 11-21-2012, 05:00 PM   #17
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You might have been a bit hasty. If they are irregular at all in shape then they are probably protein globules which are quite harmless. If they are uniformly shaped and in particular if they are paired they are the dreaded pediococcus and you did the right thing.

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Old 11-21-2012, 06:36 PM   #18
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Thanks AJ, would protein globules be moving around? Brownian motion? They were very small, so I really couldn't make out the shape. Less than 1/10th of the width of a yeast cell. They were not visible in my control or any of the other slurries. Before putting it down the drain I made up another slide being very careful about procedure and cleanliness.
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Old 11-21-2012, 06:47 PM   #19
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Yes, they are in continuous (Brownian) motion and about 1/10th the size of a yeast cell is about the right size but the real key that they aren't bacteria is that they have no symmetry i.e. they are not rods, spheres, cubes etc - just globs of stuff seemingly randomly joined together.

 
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Old 11-21-2012, 07:04 PM   #20
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It was hard to tell the shape of these objects because they were all very small. There were a variety of gobs larger than the yeast cells, but the moving ones all seemed to be about the same size. There were no structures that were irregular and the size of yeast, just these ones smaller than yeast.

What I saw looked very similar to this:
https://www.youtube.com/watch?v=8FZwKFC75XI
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