I was asked about my collimation cap recently, having referred to it a couple of times. It’s really very basic, but I just happened to find that it fitted over the rear thread of the baffle tube on my Mak rather nicely, so I drilled a small hole in the middle and used it for initial collimation of the scope and checking that the baffle tube was central. Here it is:
I fact the hole is probably too large. I reckon it could easily be taken down to 1mm diameter. I shan’t be looking for another however as I recently found a 1.25″ Astro Engineering plug, which reveals something quite useful when the sticky plastic logo is levered off:
The hole isn’t quite as small as I wanted, but the depth of the plug should make up for that.