ldflan wrote:Hi, René -
Well, higher magnifications are OK on the .55 NA DIC condenser for the Diaphot, but the results are inevitably limited and there isn't much point in using the scope as configured for that, to my way of thinking. If nothing else, using high NA objectives on the Diaphot requires super thick immersion oil, and it's a pain to clean given the configuration of the scope.
In terms of LED fluorescence light sources, I really don't think we are there yet - at least not at any reasonable price point. I haven't looked into it in a few years. If you can point me to an LED UV source that has been shown to have a broad enough spectrum to be useful with even a small range of standard fluorochromes (TRITC, FITC, DAPI equivalents at a minimum), I would love to know about it!
Hi Leonard, just try it, you might be surprised. Remember, the ubiquitous Abbe yields an aplanatic cone of just 0.65, and is still mounted on many a microscope, and used with 100x objectives; a 60x is more forgiving in terms of image quality. Our quality mark (iso 17025) was resolving Frustulia saxonica on a testslide in brightfield, no problem.
Concerning led fluorescence, I've limited the use to a UV led for DAPI and Calcofluor white (for determination of dinoflagellates). A Nichia UV LED (385nm works well) is not that expensive anymore. The thing with the Oly IMT-2 and your Diaphot is that you have plenty of room in front of the cube. Critcally was the use of a small plastic fresnel lens in front of the excitation filter, and the LED mounted at focal distance (a cm or so) in front of the cube (fresnel). No collimators or lamphouses necessary. The LED was dimmed to a great extent, so a large heat sink is not necessary. Got the fresnels for a tenner each or so from https://www.fresneltech.com, just remember to take the UVT acrylic ones for UV transmittance.
Biggest expense was the cubes. I'm sure you can think of a way to mount different LEDs in a row on a slider , if you want flexibilty in excitation wavelengths.
Good luck, René