Tonight the moon was a waxing gibbous and the sky was clear. So I hauled the telescope out and set out to capture another one of the images for my moon series. I got a couple of decent shots but in the process of trying to improve the focus to get a clearer image I noticed a problem. The image below is of the planet Mars slightly defocused. When viewing a slightly out of focus star or planet in my telescope (which happens to be a Schmidt-Cassegrain type) you should see a ring with a dark center perfectly centered. As you can see below, there is a ring but the dark area is not centered. Without getting into all the details of telescope construction, what this means is that the mirrors in my scope are not aligned properly. It is not a big deal and there is a straightforward process for "collimating" the mirrors. But the bottom line is that my images are not as sharp as they should be. So next time I take the scope out, I need to spend some time aligning the mirrors before I take more images.
 

Mars defocused. Notice how the dark area in the middle is shifted towards ten o'clock rather than perfectly centered.

To be continued.