October 4th, 2017, 9:30 p.m. local time
Last night was “Full Moon night.” The Moon passed from its prior Waxing phase and is now in its Waning phase, were it shall remain until the next New Moon.
When is the Moon truly full? If you look at my image above from last night, taken with my digital camera, you may believe this is a Full Moon. But it is more likely a 99-99.9% Waxing Gibbous. How can you tell? Notice on the right side how there is a thin circular line along the circumference of the Moon’s edge. This indicates the direction of the Sun relative to the Moon as seen from my location on Earth. Now look at the left side and note the absence of that circular line. Instead, on the left you still see the shadows of craters at the extreme edge of our viewing range.
At some point last night, yes the Moon went fully Full and the line traced a complete circle. That is your real Full Moon. Tonight, that circular line will now be on the left side with crater shadows visible on the right.
Someday I hope to capture a true Full Moon. Its appearance is relative every Moon cycle, so instead of relying on luck, whenever I have more time I will look up the exact UTC time and be ready to photograph at that moment.