Today, a most unusual event will take place: the transit (passage) of the planet Mercury across the Sun's disc. Mercury will take nearly 5.5 hours to cross in front of the Sun. First contact is when the disk of Mercury first touches the eastern edge of the sun. It takes about two minutes for the disk of Mercury to completely move onto the sun's disk (second contact). The greatest transit is when Mercury will appear nearest to the center of the sun. Third contact is when the forward edge of Mercury reaches the western edge of the sun. Two minutes later, Mercury completely leaves the sun's disk (fourth contact).
In Catania we will not be able to observe the event because today it is a rainy day.
However, a streaming of the transit live from Telescopio Nazionale Galileo is available here
The image shows the latest full disc image of the Sun in the center of the Hα line (656.28 nm ± 0.25 nm) acquired at INAF - Catania Astrophysical Observatory. The raw images are recorded with a size of 2200 x 2200 pixels and a digital resolution of 16 bit. The display is refreshed every minute. The spacing of meridians and parallels is 10 degrees.