Re: More on A.pellucida

Hi NoSpam, can you tell me where exactly this is located on the
Baertierchen site??
Also, you seem to have been lucky to be able to download Spitta's and
Carpenter/Dallinger's book, I could only get snippets which were
useless. Would you mind sending them to www.yousendit.com, so that we
could download them from there?

In return some more comments on your messages:

You stated:


The more empty magnification, the lower the contrast. 36mm fim and
3Mp cameras are more then adequate.

I stand with this conclusion. A 100x 1.4NA lens with 20mm secundary
image (such as seen with a 10x eyepiece with fieldnumber 20) only needs
2000 pixels along the middle line for all detail for all to be resolved
(ie 2 pixels for 0.2 um). If you fix a 36mm frame inside the field of
view, you will need less pixels, but add some to compensate for the
Bayer filter in the digicam, then you will have enough with 3Mp.
I agree with you, increase pixelSIZE (but not total amount of pixels)
and with corresponding extra magnification will reduce noise, but that
is irrelevant in this discussion.

I produced an image of A. pellucida by projecting the
intermediate image of this diatom upon the CCD of my *ist Pentax (n=1)
and was UNable to resolve the striae. I then projected the intermediate
image through a 2.5 projection lens (n=2.5)and could resolve the striae
perfectly well as shown at
http://www.mikroskopie-forum.de/read.php?2,25394,25394#msg-25394 .

I'm not sure exactly where your exp did go wrong. By 'direct
projection' you mean you simply took out the projection lens/eyepiece
and adjusted focus? That would increase the effective tubelength a
couple of cm from the original 160mm it was designed for. This would
create spherical abberation, ie unsharpness. Your CCD should be at the
place where the secundary image is placed (where your eyepiece 'picks
it up'), somewhere a cm or so below the rim of the tube).


Finally I wish to point out that my image of A. pellucida (see
the link in my original post) was obtained using a magnification
of 250x (100x from the objective, 2.5x from the projection lens),
while Dr. von Heurck used magnifications of 1800x to 3000x.

That would make your specimen a very big one ;-)


René.

ps, keep it up, you are learning a lot.

.

Relevant Pages

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