More On the Photon Instruments Refractor



I had mentioned a few days ago that the diagonal that came with the scope seemed a bit loose. I pulled out the micrometer and measured the inside diameter of the focuser, and the outside diameter of the diagonal. My best estimate for these is 1.994" and 1.992", respectively. A discrepancy of 2/1000th of an inch isn't enough to cause a problem. So why does it rock back and forth?



The focuser is actually a fairly large tube with a "collar" threaded into it. The collar is the 2" diameter component--but the collar's bearing surface is only a fraction of an inch deep. Once the diagonal has slipped into the collar, it is unsupported beyond the collar. I believe that this is what causes the diagonal to rock back and forth. It would take a fairly minor design change to correct this--make the collar perhaps 1.5" deep, and the diagonal would be fully supported. Fortunately, the collar is threaded, so it would be an easy change to make. Had I an engine lathe, I would just whip one out.