The Mitutoyo 10x M PLAN
The Mitutoyo 10x M PLAN APO is an absolutely fantastic microscope objective. I use it adapted to my dSLR via a 200mm relay lens for extreme macro photography, where the extra long working distance is extremely helpful. The color correction is fantastic (no purple fringing), and the image is very sharp in the center. Astigmatism becomes pretty bad in the corners of a full frame sensor, but that is well beyond Mitutoyo's quoted 30mm imaging circle.
Microscope Central had great customer service and the lowest new price I could find. Thank you so much!