Step 1: Gather Materials
A wood backer or spacer that sets the objective lens back from the ocular. The width of this depends on the slit lamp or ocular devise and is dependent on the location of the exit pupil. This distance can be obtained by holding a piece of paper in the focus beam of the ocular and measuring the distance from the ocular rim surface until the beam is nearly as small as it gets. This takes a bit of trial and error but the distance for the Haag-Striet BQ 900 spacer is 10 mm. I used poplar and teak wood for no particular reason other than it came in the required thickness. You need enough to cover the back of the hard case.
A seat post quick release clamp that corresponds to the size ocular you are dealing with. The Haag-Striet BQ 900 used a Bontrager 40 mm to fit perfectly. The BM 900 used a Tran-X 32 mm. These can be modified with a rotary sander on an electric drill to give you slightly larger diameters. The aluminum is very easy to work with. Make sure they come with "quick release" levers to allow you to put them on without the use of hex screwdrivers. The quick release should be trial fit over the ocular and checked to see when the lever is closed down if it forms a firm but not crushing grip on the end of the barrel.
Glue --I use Gorilla Glue for gluing the spacer to the case, but strong contact cement would also work. I used J/B weld epoxy to cement the quick release clamp to the wood spacer along with a screw.
Step 2: Attaching Spacer to Hard Case
Step 3: Attaching the Seat Post Clamp
Step 4: Put It to Good Use
I have not tried this setup on anything but a slit lamp but I don't doubt this same thing can be done with microscopes, telescopes, and binoculars without too much trouble. Please have fun with the design and add comments if you have found it helpful.