Dumb Focuser Thumbscrews

Last night I realized that much of the flexure in the optical train I have been noticing many times before is really caused by the focuser. It is never snug to the back of the telescope. So today I took a closer look and noticed something I should have noticed a year ago. The damage to the optical back is not caused by over tightening, but by the focuser thumbscrews that were included in the JMI case itself! Comparing them to the original ones that came with the telescope, it is obvious that these replacements have a flat head instead of a round one, and they do not properly fit in the optical back.

So I filed them. And indeed now the focuser connects well. Moving forward, this should reduce the elongated stars I have been seeing in so many of my images.

Planetary Nebula M57 Revisited

My first image using my new AO-7. Not perfect yet, but sure an improvement on my previous image.

2003-04-08: 4 minute exposure (2x120s). Camera cooled to -10-20°C.