This moment, when the eighth planet is 180 degrees from the Sun, comes on Tuesday September 5 at 5h by Universal Time. For American time zones, that is late tomorrow, Monday.
This is the evening view (enlarge it as much as you can) for Sunday, about 28 hours before the opposition. You can see that Neptune will tomorrow be at its nearest to the “anti-Sun,” which could also be called “Earth’s shadow,” the direction opposite to the Sun.
Unfortunately the bright Moon is not far away, and racing nearer. On Wednesday, Sep. 6, it will at 5 UT pass south of Neptune – close enough to occult the planet, as seen from Patagonia around midnight – and at 7 UT will be Full.
The blue circles are successive positions of the Moon’s “shadow” cast by Neptune. The diagram to the right shows Neptune and Moon as seen from Earth.
The best times to try to find Neptune in your telescope may be a few days later.
Remember that its magnitude is about 8, around 3 magnitudes dimmer than the dimmest stars visible to the naked eye.
Now. After the great August 21 eclipse, it took me several days to get home, and several more days to compose the pictures and remarks I had in mind. I had my piece just about ready on the last day of August, but had to finish it in a hurry, because I was summoned away for a night and a day. So, as almost always happens, some adjustments occurred to me. If you care to look again at my “Eclipse over Lake and Tower,” you will see that it begins with four pictures instead of three; and there are slight changes and additions of wording. (For instance, I was mistaken in saying that I got to the Indonesian eclipse by bicycle.)
I like the comments y’all have made. David Stroud and his sons “started at 1st contact and did not quit observing until 4th contact!” which is fairly unusual; most people drift away as ordinary daylight returns. Rick Scheithauer saw a mountain “blink out” in the moon’s shadow. Jack Gambino contributed to the evidence on animal behavior a frightened baby screaming at the darkness but a dog sent to sleep by it, and asked surreally: “Who’s going to clean up all these crescents?”