No worry about hijacking, Bill, I'm really enjoying the knowledge that is passed here. I ordered a couple of IR pass filters a couple of weeks ago, to see what I could do with them on my Lodestar or ST-I guiders. I did look at Thorlabs at that time and noted the better surface accuracy of their mirrors but, being 79yo, promptly forgot about them!
As mentioned here though, using the guide camera with an IR filter will make it more difficult to find a suitable star but I will test that when they arrive. My cameras are QSI wsg and their prism is fairly small.
I've got plenty of time, and most of the skills to precisely engineer this project but will take note of what is said here. I'm not too concerned yet, about BF for the guider as one can easily guide with slightly out-of-focus stars and, being a DIY, I can hack into a homemade ONAG if neccessary. I couldn't ever do that to a commercial one like the SharpLock system!
