I’ve had my dobsonian telescope for about a month now and have had it out several nights. When looking through the collimating cap, everything seems to be fine.
My question is about performing a star test. I have a pretty bright star centered in the view and I defocus it. Instead of a series of concentric circles (like all the online examples) The star just turns into a single halo. Not smooth at all, but very jagged. Imagine a high frequency sine wave that was cut and wrapped into a circle.
I get clear views of Jupiter and Saturn at 200x, the moon looks clear and stars are usually pinpoints of light and not distorted. Could my star test results be bad seeing, or user error? Any experience with this?