Arachnoidiscus ornatus on a strew slide from Santa Ana, California. Collected by JD Solliday. Prepared by Mike Samworth. Mounted in Naphrax, dated 1999. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo NA 1.40 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, slightly oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 23 images stacked in Zerene (Pmax).
The images above shows one of the benefits of using Naphrax – its high refractive index (RI of about 1.73) in relation to the diatom frustule (about 1.43). In another slide by Mike Samworth, Arachnoidiscus ornatus has also been mounted in Eukitt which has an RI quite close to diatoms (Eukitt RI 1.49). Imaging this Eukitt mounted slide using the same setup as above, gave the following image which had much lower contrast. Also shown below is the Eukitt slide.
