Mercury, the ’innermost planet’, reaches its greatest eastern elongation on April 1st, 2017. Thus these days, observers of northern-based locations (as, within this cycle, the opportunity of Mercury’s evening visibility for stargazers in southern hemisphere won’t come) should be able to catch this planet, seldom visible to the naked eye, low down above the western horizon just after sunset (see chart below).
Mercury’s orbit lies close to the Sun (maximum elongation is between 18° and 28°), meaning that it is observable at best not more than for a few days each time it reaches greatest separation from the Sun.
After April 1st, Mercury sinks gradually back towards the horizon until it becomes lost to the bright twilight, roughly 10 days later. >>> More Info