As you correctly pointed out, when Mercury is directly behind the Sun or nearly so, it’s invisible to us. But when it’s almost behind the Sun, but at enough of an angle to be visible, it’s then at essentially its farthest away point, and thus at its brightest magnitude. At this point, Mercury is in its “full” phase, although it is also tiniest in size, yet at its most brilliant. This is opposite to the behavior of Venus, which is brightest when on the nearer side of the Sun to us, and though a crescent and therefore mostly showing its night side, it’s displaying its largest amount of surface area.
Hi Barry,
As you correctly pointed out, when Mercury is directly behind the Sun or nearly so, it’s invisible to us. But when it’s almost behind the Sun, but at enough of an angle to be visible, it’s then at essentially its farthest away point, and thus at its brightest magnitude.
At this point, Mercury is in its “full” phase, although it is also tiniest in size, yet at its most brilliant. This is opposite to the behavior of Venus, which is brightest when on the nearer side of the Sun to us, and though a crescent and therefore mostly showing its night side, it’s displaying its largest amount of surface area.