When a persons horoscope is having any of the following placements of Planets , there occurs a serious problem in the horoscope known as Chandra Grahan Yog or Chandra Grahan Dosh. When the Planet Moon and Ketu are placed together in the same house or they are aspecting each other then it is known as Purna Chandra Grahan Dosh.
When the Planet Moon and Rahu are present together in the same house or they are aspecting each other then it is known as Partial Chandra Grahan Dosh.
Apart from this whenever the Mahadasa of Moon and Antardasa of Ketu comes and whenever the Mahadasa of Ketu and Antardasa of Moon comes, then this period is also known as Purna Chandra Grahan Dosh.
Apart from this whenever the Mahadasa of Moon and Antardasa of Rahu comes and whenever the Mahadasa of Rahu and Antardasa of Moon comes, then this period is also known as Partial Chandra Grahan Dosh.