A friend pointed out my star trails were blurry and it was a simple fix

I was really proud of a shot I took of the Milky Way from a dark sky site near Flagstaff. I posted it online and a friend, who is also an astrophotographer, sent me a private message. He said, 'Your core is sharp, but all your star trails at the edges are soft. Check your back focus.' I had no idea what he meant. After looking it up, I learned my camera sensor was too far from my telescope's reducer. I bought a set of small metal spacers, about 5mm thick, for twenty bucks. Adding one spacer moved the sensor to the exact right spot. The very next time I went out, my stars were pinpoints from corner to corner. It made such a huge difference in image quality. Has anyone else had a similar 'aha' moment with gear setup that fixed a nagging problem?

2 comments

2 Comments

the_elliot10h agoTop Commenter

That's not back focus, that's field curvature.

morgan8981h ago

I always called it back focus too, but @the_elliot just changed my mind on that.