[Microbiology] Re: worm count

Juergen Wiegel, via microbio%40net.bio.net (by juergenwiegel from gmail.com)
Sun Feb 27 17:28:50 EST 2011


Larry gave you a good suggestion:  to get in contact with a University and
see to get a scope from their surplus and then make an "unrestricted
donation" to the Department (tax deductible) and get some help from a
faculty or graduate student to help you to  use a microscope efficiently and
insuring correct identifications of your various possible worms.
HAVE FUN. THE WORLD  THROUGH THE LENS OF A MICROSCOPE IS ALWAYS FASCINATING.

Juergen Wiegel
Distinguished Research Professor; Emeritus
Depts. of Microbiology and of Biochemistry & Mol. Biology
University of Georgia
Biological Sciences Building Rm 211-212C
1000  Cedar Street
Athens, GA 30602-2605  (USA)
Tel. 706-542-2651 (combined voice and FAX)
Dept. Fax 706-542-2674



On Sun, Feb 27, 2011 at 11:22, Larry Farrell <farrlarr from isu.edu> wrote:

> On 2/26/2011 10:03 PM, Joy Young wrote:
> > I  live on  a farm and looking to buy a microscope to do worm count on my
> animals, I wondered if a student microscope would be satisfactory I am told
> that I require a magnification of 100 x 400.  I am not familiar with
> microscopes but would be pleased to learn.
> >
> > Joy Young
>
> You will not need a magnification of 100 x 400 (a total magnification of
> 40,000X); studying bacteria only requires a 10 x 100 magnification(a
> total of 1,000X), and there is no reason to go much beyond that total
> magnification because the optical properties of light make anything much
> beyond that level what is called "empty magnification."  That is,
> although the scope is theoretically capable of magnifying beyond that
> level, it doesn't give you any more information about the subject than
> what you can see at 1,000X.  A student microscope will work fine,
> depending on what kind you get.  If you look at toy store catalogs and
> get what they call a student microscope, it probably will not be worth
> your money/time.  Instead, I suggest that you check out Edmund
> Scientific online and plan to spend at least $150-200 on one of their
> scopes.  If you can afford more than that, even better; the more money
> you put into the scope, the better optics you can expect.
>
> Realistically, "worm counts" will probably not require anything beyond
> about 400X (10X eyepiece times 40X objective).  If you go much beyond
> that level of objective, you will need to use oil to observe your
> specimen (oil objective lenses are sufficiently high magnification that
> too little light can be captured directly to allow you to see; the oil
> prevents the light from bending outward, away from the lens, and results
> in more illumination) and that is messy and unnecessary, given what you
> will be looking at.
>
> If there is a college or university in your area, I strongly suggest
> that you (1) consult with some of the biology faculty about your needs,
> discussing specifically with them what type of scope to get, and (2) see
> if they have any surplus scopes you might buy (that would assure a
> reasonable level of quality and function; if the scopes have held up
> under student use, they should work well for you).
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