Diatoms in high nA DF.

myriophyllum · Post by **myriophyllum** » Fri Mar 17, 2017 3:54 am

Hi,

I've been playing around with the Leuchtbild condenser...
This time the goal was to get darkfield with a 63/1.4 oil immersion lens without stopping this lens down.
Placing a 14 mm stop below the condenser was the key to do so...

The diatoms were embedded in Naphrax, found at the Hagenburger Kanal, Schaumburg, Germany.

The pictures:

Detail:

Central stop in offset position:

+
finally one more A.P.:

Technikque: Zeiss Standard 18; Planapo 63/1.4Öl; Leuchtbild condenser;
S-Kpl 16x/12,5 and Kpl 20x/8; relay lens f=63mm; Canon EOS 5DII.

Best wishes
Jens

zzffnn · Post by **zzffnn** » Fri Mar 17, 2017 6:59 am

Very nice work, Jens!

Your Leuchtbild condenser is an 1.4-1.6 NA one, correct? So centering a 14mm opaque stop under the condenser was all that was required for a full NA 1.4 objective to work?

I wonder if I can do something similar, with a 1.2-1.4 DF condenser, for a full NA 1.2 objective.

Thank you for sharing!

PS: I think you will resolve even more dots, if you image diatoms that lay perfectly flat on cover slip.

myriophyllum · Post by **myriophyllum** » Fri Mar 17, 2017 7:24 am

Hi,

Thanks a lot. Right, flatness was a problem.
The designer Henry Siedentopf of Zeiss wrote about a maximum nA of 1.5 (Lit.: Kolloid-Zeitschrift; December 1925, Volume 37, Issue 6, pp 327–335; Ueber Neuerungen zur Dunkelfeldbeleuchtung; Henry Siedentopf).
The glas of the slide wouldn't give more anyway...

I think, the 14mm stop makes a 1.45 - 1.5 nA range, quite low light.

I don't have a nA 1.2 objective here, but it should work this way with an Ultrakondensor or other 1.2 - 1.4 condensers. The diameter of the stop needs to be determined very exactly...

Greetings

Jens

zzffnn wrote:Very nice work, Jens!

Your Leuchtbild condenser is an 1.4-1.6 NA one, correct? So centering a 14mm opaque stop under the condenser was all that was required for a full NA 1.4 objective to work?

I wonder if I can do something similar, with a 1.2-1.4 DF condenser, for a full NA 1.2 objective.

Thank you for sharing!

PS: I think you will resolve even more dots, if you image diatoms that lay perfectly flat on cover slip.

carlos.uruguay · Post by **carlos.uruguay** » Sun Mar 19, 2017 4:57 pm

myriophyllum · Post by **myriophyllum** » Wed Mar 22, 2017 9:55 am

carlos.uruguay wrote:Nice

Thank You, Carlos.

Yours
Jens

GaryB · Post by **GaryB** » Wed Mar 22, 2017 12:06 pm

I really like the 'cosmic' aspect to the look, very spacey!