HERE
Rik commented "In theory, if a dry objective is designed to expect a cover glass then you can always add one. Just stick it on the end of the lens if you need to -- it can go anywhere between the objective and the subject as long as it's properly parallel."
Up until now I have been using a Nikon 4x objective without a cover glass.
Today I followed Rik's advice and taped a cover glass to the front of the lens.
One of the local ants, possibly a New York Carpenter Ant ( Camponotus noveboracensis).
Unfortunately the ant moved during the exposures and so I can't show an actual pixel shot from the 62 frames.
I can show a stack of 5 frames (lower image) where there was no movement.The actual head length is 1700 pixels and I have reduced it to 1000 pixels. Image quality seems OK, appears not to be degraded.
Of course I will have to run the test again to compare 'with cg' vs. 'without cg' - but not tonight!
Nikon CF Plan 4x/0.13 160/- Achromat, 62 frames @ 0.02 mm, Nikon focus block, 2 flashes, styrofoam cup diffuser.
Top image with a few dust spots removed.


NU1011 & NU10012