Re: DIC On An Amateur Budget

On Jul 27, 7:15 pm, "NoSpam" <NoS...@xxxxxxxxxxxxxxxx> wrote:
Dear Group,

Significant savings can be had by not considering a full range
of objective magnifications. For work with protist the 40x
objective is probably the most useful and certainly all that
is needed to start.

Greetints
GR.

"Perl" <thl4...@xxxxxxxxx> wrote in message

news:1185559078.820581.44110@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi

Wonder how much is amatuer Budget ??

Regards
Pär Liundqvist
Sweden

Hi,

With respect to protists I think the contributors who suggested the
use of 40x and 16x objectives were correct but you will need both.
Generally not much more detail is perceived with 40x than with 16x for
these specimens and the wider field of the lower magnification
objective allows motile organisms to be tracked more easily. 40x is
fine for studying bacteria and as they have little visible internal
structure there is generally no advantage to using a 100x objective.
Indeed, I rarely use 100x for bacteria or protists, other than
prepared diatoms.

I hardly ever use the 6.3x objective because setting up for it is
tedious. One has to unscrew the 1.4 NA condenser lens, which has an
incredibly long thread, and insert a lower NA lens. I merely use this
objective in a crude brightfield with the 1.4 NA top lens and the
condenser lowered, it's quite good enough for most observations and a
kind of oblique contrast can be attained by shifting the filter holder
a little.

I am referring to the second of the three 160 mm Zeiss systems which I
mentioned in a post in another group. I also mentioned there that this
system gives acceptable DIC with several neofluar and apochromatic
objectives although it is optimised for planachromats. One advantage
of this is that you can use a set of neofluar phase contrast
objectives (100x, 40x, and 16x) and switch immediately from phase to
DIC. The condenser has phaco 2 and 3 positions which means 6.3x phase
contrast cannot be used unless you have the planapochromatic version
(I haven't a clue whether this would give good enough DIC with this
system). Anyway, the planachromats are fairly cheap so there's no
reason why you could not have a set of optimised objectives for
critical work as well.

I think someone mentioned that adjusting this Zeiss DIC system is
fiddly. I have not found it so. Incidentally, the Zeiss manual
recommends oiling the condenser for all DIC work. This, for < 100x
objectives, doesn't seem necessary. I discern little, difference and
only oil occasionally. The condenser needs to be nearly touching the
slide and so the only other critical thing is aligning the optical
axis.

An interesting feature of the Zeiss system is that the analyser
(housed in the intermediate tube) has a long range of travel. Thus,
not only can one obtain the optimum grey background DIC image but also
beautiful blue and red backgrounds. Perhaps someone else could comment
on the capabilities of other DIC systems in this respect.

Selwyn


.

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