On September 14th. Mercury will reach “greatest eastern elongation” meaning Mercury will be best viewed just after sunset all mid-September!
To see Mercury look to the west after sunset the main trick here is you want to look a bit after sunset when it’s dark enough that Mercury is visible but if you wait too long Mercury will set. around 8P has been about perfect for me. Mercury will be fairly low on the western horizon at sunset so it is best seen when you have a clear view of the western horizon, which can be difficult from the front range with the mountains directly west of us. I am seeing it where I am in Boulder even with the mountains towering to the west but you will have a better time the further east you go (or even better from a mountain peak).
Mercury was named after the fastest god Mercury with wings on his shoes because Mercury (the planet) moves really fast! Watch Mercury over the next few days and you will see why. Just over the month of September you can watch Mercury bolt into and out of our evening sky.
This is because Mercury is the innermost planet; it's able to race around the sun once every 88 days. If you missed it this time save the date for October 25th 2021 when you'll be able to see it in the east just before sunrise!
This is a fun age calculator that will tell you your age on other planets: https://www.exploratorium.edu/ronh/age/ you will always find Mercury to be the largest since it’s the quickest to get around the sun!
Because Mercury orbits the sun so close and the earth’s orbit is much further from the sun Mercury never gets more than about 20 degrees from the sun in our sky. Astronomers only really count twilight as being over when the sun is more than 20 degrees below the horizon. Meaning you only really see Mercury during twilight making it one of the hardest planets to spot!
The Main thing to see with Mercury in binoculars/telescopes is its phases. Just like the moon Mercury as phases and they are slightly visible in good binoculars or a telescope. You should beagle to see a little lopsidedness to the dot when looking and if you have a good telescope you might beagle to see what phase it's in.
If you want to see Mercury up close in a big telescope book a tour around September 14th AstroTours.org/booking