Mercury in October
Easing into the Evening As was true in September, Mercury is technically moving into the evening sky, but it is not well-placed. The ecliptic makes a very shallow angle with the horizon in the autumnal evening. Even though its angle away from the Sun will increase this month, it will be low in the trees for most of us who do not enjoy an unobstructed horizon. At any time, Mercury can be a challenging object. For sunset apparitions, one must have a reasonably clear western horizon. I like to point out that, in over fifty years of observing the sky, I have seen Mercury fewer than half a dozen times. Maybe if I tried a little harder, I could catch a glimpse a few times a year!
Carpe Caelum Mercury This Month