On Thursday, August 17th I got about an hour’s worth of clear sky – just enough to point my telescope at Vega as a collimation target that was directly overhead.
After pointing it at Vega, I defocused the image until I had a donut large enough to see that it was not centered. I then took a piece of plastic about 25 mm wide and 100 mm long and lined it up with one set of push/pull screws and imaged to see where it fell on the donut. Once I determined which screws were associated with what area of the donut, I made an adjustment on the ones aligned with the thinnest part of the donut to move it to center. I performed a few iterations on this and tweaked it on a second set of push/pull screws until was where I felt in an ideal spot.
Adjusting those push/pull screws is critical. If you adjust a pull screw say ¼ turn loose, then tighten the push screw and check. If it is not right, reverse that process and go back to your original position. The tolerance on the Hyperstar’s backfocus is very tight, so you don’t want to go moving a lot. Think small steps and keep testing. Test as much as you are comfortable with. Adjust in very small increments as ¼ turn is a lot.
I wanted to get my tri bahtinov mask on it at that point but could not get it to sit in there right so will have to return to this when I get the right focus mask, but that will let me tweak it for good.
The image in this blog article of M57 was taken post-collimation which as you can see is much better.
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