Today my one foot length of 1 1/2 inch dia acrylic tube arrived, and with some difficulty I cut off a piece for the housing. First I found that the vendor had not cut the tube square on both ends, so I marked off a 21/32" length and used a small plastic miter box from HD and a hack sawa to cut it off. My cut was 1/32 out of square. So, I cut about a sixteenth of an inch off taking care to keep it square, then hand sanded it so it was square. I then clamped a "stop" to the miter box 11/16 inch from the blade, and cut that while slowly rotating the tube with the end hard against the stop. That worked very well, so after sanding to clean it up, I have my housing.
Next problem: the tube is 1 1/4" ID and the cylinder from the lux meter is also 1 1/4 " OD, so it won't fit inside the tube. Tomorrow I will sand either the inside of the tube or the outside of the cylinder until they fit together. (Probably inside the tube so I don't have to handle that lux meter cylinder any more than necessary.) As with any DIY project, each step hands you another little problem.