I just received a mail asking how you collimate the Sky 90. I do not have a Sky90 in front of me, so some of this will be down to my failing memory. From memory I think there are 3 adjustment screws (widely spaced) sitting behind 6 adjustment screws (more closely spaced). Don’t touch the 3 adjustment screws but do all the collimation with the 6 screws.
You now need to buy yourself an artificial star, which is no more than an LED behind a tiny Aluminium aperture. Set the artificial star about 30 feet away from the Sky 90 and get an image of the star on a webcam fitted to the Sky90.
Now I think the software I had that made the collimation a doddle was Sharpcap, but I couldn’t swear to it, but it made setting up very easy as it locked on to whichever artificial star you click on (I worked with the smallest aperture).
It is now a good idea to have 6 Allen keys, one for each adjustement screw, or this will be a VERY long process. Focus the artificial star and then move very slightly IN and OUT of focus to set up the collimation on both sides of focus. With the Sky90 slightly out of focus (on either side) you should see Airy rings, and the central ring will be displaced from dead central of the ring pattern. You now have to see how untightening/tightening the adjustment screws moves the central Airy ring. Adjust the screws until the central Airy ring is dead central on both sides of focus.
That’s it. From a fresh start it probably takes me around 4 – 6 hours with several breaks. It is very tedious.