Observing log

An observing log is the astronomer's lab notebook. For each session it records where you were, what the sky was like, what equipment you used, and for each target, when you looked and what you actually saw. Observers have kept such logs for centuries; observing programs such as the Astronomical League's certificates still ask for one as proof of observation.

The log matters because the same object looks very different with different skies, apertures, and magnifications. "M13 resolved to the core at 150x in steady seeing" means something next year only if you know the scope and the sky that night. A good log also records failures honestly: "not found" and "suspected only" are real observations.

When to use it