Ian Spangenberg Popular Astronomy Club September 2019
Go to this link and type in your city: ◦ https://www.timeanddate.com/moon/ This website provides the rise, meridian, and set times for the Moon. ◦ Moonrise: when the Moon just comes up over the horizon – you will probably be able to see the Moon 10 minutes or so after this time if you aren’t surrounded by tall trees (if there are no obstructions on your horizon). ◦ Moonset: when the Moon sets below the horizon. ◦ Meridian: without getting into a bunch of complex concepts, it is basically when the Moon is up highest in the sky. This will be the best time to view the Moon, but anytime between Moonrise and Moonset would be great. The link on the previous page also provides information about ◦ Rise/set times for the Sun and planets ◦ Eclipses ◦ Moon phases (but I have a different website for those) ◦ Time and time zones Last quarter is also known as 3rd Quarter
One side of the moon is always illuminated. There is a dark side of the moon, but it is not permanently dark. Let’s look at 1st Quarter. If you are having trouble visualizing it, The sun is illuminating the draw in a stick figure right side of the moon. standing on the Based on how the Earth is Earth’s surface and looking at the Moon, we looking “upwards.” I see a “half” moon. We can’t did that on the next see all of the illuminated slide. side of the moon. We see half of the dark side and half of the light side.
https://www.moongiant.com/calendar/Septe mber/2019/
You can compare your drawings and descriptions with the “official” moon phases. In general, the Moon goes through each phase about every 3.5 days. In other words, it is full moon for 3.5 days, then it is waning gibbous for 3.5 days, etc. This can be very difficult to see in your mind. You really have to sit and think about it. Look back at the moon phases picture on the last slide. Full moon can only occur during the nighttime. The stick figure standing on the left is having nighttime, because the Sun is illuminating the other side of the Earth. If the moon is on the left side of the Earth, people will never be able to see the Moon on the daytime side of the Earth. Those people would have to look through the Earth in order to see the Moon. Consider how people experiencing night time would have to look through the Earth to see the Sun. It’s the same thing. If you are having daytime, you have to wait until the Earth spins around on its axis to turn into being able to see the full moon. Essentially, the moon stays more or less stationary from day to day (remember it takes 30 days for it to orbit the Earth). So, the Earthlings experiencing daytime (stick figure standing sideways on the right of the previous slide picture) must turn into being able to see the Moon. Similarly, you see 1st quarter moon high in the sky in the evening, as daytime is turning into nighttime. You see third quarter moon high in the sky in the morning, as nighttime is turning into daytime. On the next slide are the times of day at which the Moon phases will hit their highest point in the sky before they start to set. In general, the moon is up in the sky for about 12 hours because the Earth takes about 24 hours to do a full rotation (the daylength).
Blue Moon ◦ The 3rd Full Moon in an astronomical season with 4 Full Moons A season is 3 months long (summer is June, July, August, for example). A lunar cycle (from full moon to full moon) is about 30 days. So, you can only have 3 full lunar cycles in one season. But, if one full moon happens at the very beginning of the season, you can actually have 4 full moons during the season. ◦ The 2nd Full Moon in a month with 2 Full Moons. Again, a full lunar cycle is 30 days.. ◦ The Moon, full or any other phase, can appear blue when the atmosphere is filled with dust or smoke particles of a certain size; slightly wider than 0.7 micron. The particles scatter the red light, making the Moon appear blue in color. This can happen for instance after a dust storm, a forest fire, or a volcanic eruption. Harvest Moon ◦ The Harvest Moon is the full Moon nearest the start of fall or the autumnal equinox. This occurs every year somewhere in September 21st, 22nd, or 23rd. Super Moon ◦ The Moon’s orbit is not a perfect circle. It gets closer and further away over the course of the orbit. A super moon is a full moon that is at or near perigee, or the point where the moon is closest to Earth. This is essentially the opposite of a Strawberry-moon, which refers to a full moon that occurs at apogee, or the point where the moon is farthest from the Earth. Above is a picture of a “normal” moon compared to the supermoon as seen on Earth. Unless you really knew how big the moon usually looks, most people can’t tell the difference. Strawberry Moon ◦ A full moon that is at or near apogee, the point where it is farthest from Earth. This is the opposite of a supermoon.
Astronomy Picture of the Day ◦ Posts a picture every day with a informational blurb ◦ Download the APOD app on your phone and have it update your phone background every day Sky at a Glance ◦ Stuff to check out in the night sky, updated every week Stellarium ◦ Free software program that works like a planetarium. You can set the location and the date to see what objects are up in the sky.