par focal distance / tube length

[sombre]

Hi everyone,
My microscope is an Olympus bh2/bhs.
My question is, how do I work out the amount of extension required when
I attach my Nikon D7200 in order to maintain the 160mm par focal distance.
ie:- between which two points do I take a measurement.
Hope this makes sense, as you can probably tell i'm new to all this.
Many thanks in anticipation of someone switching the light on to my query.

[75RR]

This should help answer most of your questions:

These are links to some articles that Charles Krebs has kindly written to help people set up their cameras.

http://www.krebsmicro.com/pdf/trinoc_a3.pdf
http://krebsmicro.com/photomic1/photomic1.html
http://www.krebsmicro.com/parfocal/index.html

If you have not seen Charles Krebs' photographs you are in for a treat.
Last link is to his website.
There are additional articles on there.

http://www.krebsmicro.com/