Constellations.

The constellations that astronomers use to identify parts of the sky are not the same as the Zodiac signs used by astrologers. The Zodiac signs were identical to the constellations 2000 years ago when their modern names were first used. The Signs are an astrological convenience ignoring the differences between two different types of solar calendar. This is described further in The Calendar. The astrological signs are about a month out from the astronomical constellations. When …

…the Sun. On 21st June the Northern hemisphere passes through the Summer Solstice. 2000 years ago the Sun would have been in front of the stars that we call Cancer at this solstice. Hence the Tropic of Cancer. In fact at this solstice now the sun would be in Gemini. If a Total Eclipse of the Sun were to occur at the solstice, the stars of Gemini would be visible around or near the sun. --------------------------------------------------------------------------------