First steps

Re: First steps

Postby admin » Tue Dec 08, 2009 12:25 pm

Leif. I sense that if you want to put pen to paper (as it were) it would make a valuable addition to the store of experience for beginners to draw on. We need more of this kind of thing. Go to it, please! Copy for the Forayer would be welcomed.

MJ
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Re: First steps

Postby jonathan need » Sun Dec 13, 2009 8:18 pm

Ok ,
not wanting to seem totally ignorant, but i am very new to studying fungi under the microscope.

Can anyone help me with the process to measure spores..
I have a pretty good microscope with graduated scale but need some direstion im afraid.
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Re: First steps

Postby admin » Mon Dec 14, 2009 10:38 am

Jon

When you talk about a graduated scale I think you are probably referring to the little engraved glass disc that sits in the optic and is technically called an eyepiece graticule. It has a series of graded marks, usually from 1-100. But in itself this will not enable you to measure spores. It first has to be calibrated using what is called a stage micrometer. The latter looks like a ringed glass slide but in its centre is a minute scale, very accurately engraved, which should be in not less than 0.01mm divisions across 1 millimetre (there are variations of scaling but 0.01mm is fairly standard). Using this stage micrometer, the eyepiece graticule is then calibrated for each separate objective. Needless to say the engravings on the eyepiece graticule will have different values according to whether you are using x100 mag, x400 mag, x600 mag or x1,000 mag.

The calibration process is fairly simple but it does require access to a high quality stage micrometer. Don't be tempted to buy a cheap one, which will probably have useless 0.1mm divisions or badly engraved lines. It's better to borrow a good precision job, and these are expensive (around £100 from e.g. Pyser). Once the eyepiece graticule is calibrated, measuring spores is not unduly difficult. In essence you line up one end of the spore against one division of the eyepiece graticule, count off the number of divisions (or part divisions) to the other end, and then do a simple calculation using the calibration chart that you will now have at your hand to get the actual number of microns.

The ABFG produces a good and comprehensive set of instruction sheets for calibrating a microscope and then measuring spores, which you may like to have.

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