Substitute for Reticule

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linuxusr
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Substitute for Reticule

#1 Post by linuxusr » Thu Apr 29, 2021 9:36 pm

I don't need exact measurements of specimens, so I don't need a reticule. I googled. Is this correct?

F.O.V. / objective magnification (1000) = diameter of viewing field
(F.O.V. = field of view found on eyepiece). I have WideField, 22 mm, so:

4x = 5.5 mm or 5,500 μm
10x = 2.2 mm or 2,200 μm
40x = 0.550 μm
100x = 0.220 μm

You could also estimate distance to radius and divide any above value by 2.
Maybe on a scientific caluclator I could have gotten more place values.
Nikon AlphaPhot 2 < Zeiss Primostar 3, Full Köhler; Axiocam 208 Color < UHD LG
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MichaelG.
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Re: Substitute for Reticule

#2 Post by MichaelG. » Fri Apr 30, 2021 9:05 pm

It would be wise to check those dimensions physically
The first two are dead easy if you have scales on your mechanical stage
...The two higher magnifications will be trickier but you could, for example, look at the structure of a known webcam sensor or some such.

MichaelG.
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linuxusr
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Re: Substitute for Reticule

#3 Post by linuxusr » Fri Apr 30, 2021 11:11 pm

@MichaelG

Ditto on "Too many projects."

Could be. On the other hand, I am plugging known values into a formula.

Regarding checking the 4x and 10x objectives, I still have to learn how to use the Vernier and main scales. I have a caliper to practice (easier) and there's a ton of YT videos. Haven't gotten to that point yet. I always just used the estimate per above.
Nikon AlphaPhot 2 < Zeiss Primostar 3, Full Köhler; Axiocam 208 Color < UHD LG
Aller Anfang ist schwer.

MichaelG.
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Location: North Wales

Re: Substitute for Reticule

#4 Post by MichaelG. » Sat May 01, 2021 6:04 am

It’s O.K. to use a formula; if you are sure that the numbers you plug-in are valid.

The truth is that the lens markings are ‘nominal’ ... so it’s wise to calibrate what you are using.

MichaelG.
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75RR
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Re: Substitute for Reticule

#5 Post by 75RR » Sat May 01, 2021 8:35 am

.
If you know your field of view dimensions then you could rather 'roughly' calculate the size of an object by whether it occupied 1/2, 1/4 or an 1/8 of it.

I tried that for a while when I first started out. A lot less accurate and more work than popping in a dedicated eyepiece with reticule.

As to how accurate one needs to be - I round off to the nearest 5µm on anything largish, say 50µm +

You can pick up a no name stage micrometer and a dedicated eyepiece quite economically.

http://www.ruf.rice.edu/~bioslabs/metho ... uring.html
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
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