Phases of the Moon

Since I entered the hobby in the summer of 2014, full-disk lunar observing and imaging has remained a simple yet enduringly pleasing activity for me. No matter how bad the light pollution is, Luna never fails to shine brightly in the sky. In spite of one side tidally locked into place from our perspective here on Earth, the Moon wobbles slightly as a result of lunar libration. As a result, it offers subtly different things to see each time it makes its regular monthly appearance.

For years, I used eyepiece projection to capture images of the Moon. The technique is simple: bring the telescope to focus, aim a cell phone or point-and-shoot camera into the eyepiece, and snap a photo. Although holding the imaging device by hand can yield surprisingly good images, eliminating camera movement during exposure is best. Placing the camera on some kind of brace and using the self-timer to fire the shutter yields the sharpest results.

After using eyepiece projection for years, I am just starting to get more serious about imaging the Moon. With my Canon EOS M200 mirrorless camera attached to my 3.5-inch Standard Questar, I have been able to step up my game significantly. Although running the Questar’s motorized drive keeps the Moon in the field of view, I am continuously surprised to see what is possible by taking photos even at a relatively slow exposure speed with the scope’s tracking motor turned off.

Having built a collection of lunar images, I used data from the JPL HORIZONS data and ephemeris computation service to determine what percent of the Moon’s disk was illuminated when I took each photo. I was then able to sort my collection by that figure and pick out the best images.