I have a B&L lightweight 800mm mirror - like this one: https://astromart.co...irror-lens-9712
It takes decent photos, but I think one edge of the mirror is out of focus when the rest is in. Does that indicate a need for collimation? I've attached a sample.
If so, I've seen in other places how to open up to get to the adjustment screws, but how does one collimate a mirror lens like this?
Thanks for any advice!