Following class on Wednesday, in which we discussed the lunar cycle and the moon’s appearance to us here on Earth, I looked up at the Moon while walking to my car. It appeared to be in the waxing gibbous portion of its cycle, which made sense because it was late in the afternoon and fairly low in the sky, and waxing gibbous moons rise in the afternoon.
However, I was anticipating that the shadow on the moon would essentially be at a vertical, like in the picture above, but I noticed it was tilted, like in the picture below.
Stellarium Screenshot by Colin Gerrety
Upon further investigation in Stellarium, I discovered that the tilt of the Moon’s shadow actually changes throughout the course of the night. This is not because of any change to the shadow, but how we are viewing the moon from Earth. The way we view the Moon in the northern hemisphere, the first picture of a waxing gibbous moon is how we view the Moon when it is highest in the sky. However, when it is lower in the sky, the shaded part of the Moon appears slightly tilted. This is because we are facing different directions while viewing the Moon at different points in the night. At moonrise, we face East to view the moon, and when it is highest in the sky, we face South. The “non-shaded” side of the waxing gibbous moon always faces West, and when we face East to view the Moon at moonrise, the side facing West is the upper half.
Astronomy 201 Blog 
I noticed the same thing! I was expecting to see a vertical line like we drew in class but then noticed that this “tilt” is due to our perspective from earth, depending on the time of day. It’s interesting how much more I take notice to these things now that I’m in this class.
Colin, this is really cool that you used what we learned in class and applied it to your life. I am impressed that you were able to acknowledge the moon phase from the sky and validate your reasoning based on what time the moon should appear at the horizons. Have you ever thought about trying to observe a full moon cycle to see the noticeable illumination differences? I think I may try that next month to really be able to apply our class material to the real world. Also, I like the details you included that the tilt of the shadow is not due to a change in the shadows but due to a change in the way we are viewing it from Earth. I think this point is really important for students who are new to astronomy and are unaware of how things are affected by our Earth’s tilt.
If yall have time you should definitely take a look at Juliette’s post about the “moon” app. It seems super cool and relevant to the convo!