Do you want to see Mercury?
Mercury is difficult to observe from Earth because it is always near the Sun. It can therefore only be observed in the evening shortly after sunset or at dawn.
In the spring, Mercury is easier to observe in the evening sky, in the autumn in the morning sky. Of course, this is only possible if Mercury is currently on the ‘right’ side of the sun, so in the spring only after the sun goes down and in the autumn before the sun rises over the horizon.
On the other hand, it is difficult to find in the morning sky until early in the morning, and in the autumn it is barely to be discovered in the evening sky. This is due to the position of the ecliptic in these seasons.
View the Changing phases
If you want to observe the little Mercury, it is best to use binoculars, even better a small telescope. Then you can not only watch his waning or increasing sickle but even find him in the daytime sky. However, the view must be very clear – and the sun should be covered by clouds. Or you use the shadow of a building. Its frequent transits from the sun can also be observed well, but only with a telescope – and always with a special protective film for telescopes!
Two months in the evening, two months in the morning in the sky
The innermost planet is moving fast: Mercury races around the sun in only 88 days – four times in each year of the earth. As we also turn around the sun during this time, Mercury overtakes us three times a year. Three times he wanders exactly between us and the sun through its lower conjunction – from the evening to the morning sky. Mercury revolves around the sun at a small distance and therefore always stands near it in our sky – at most a constellation to the west or east of it.
Its orbit is so elliptical that its distance from the sun varies widely. For westerly or easterly elongation, its angular distance may reach 28 degrees, when at the same time it reaches the aphelion of its orbit, the most remote point. This happens exactly twice a year: in the spring west of the sun, in the autumn east of it. Mercury could, therefore, be found in the first case in the morning sky, in the second case in the evening sky.
Mercury is the innermost planet orbiting the Sun at an average distance of 58 million km. It takes only 88 days to complete one round.
But just at these times, the ecliptic, the planetary plane, runs very flat across our sky. Although Mercury is 28 degrees from the Sun in the sky, but only slightly above the horizon in the diffused dim light, it would be better to see it at the same time as the ecliptic is very steep – during dusk in spring and in the morning in autumn. But then, for the greatest elongation, Mercury only reaches an angular distance of 18 degrees to the sun, because it is in the perihelion, the nearest point in the sun’s orbit.