In Astrology, Mars and Sun are considered as fiery planets. Perhaps that may be the reason they are good friends. But due to their bad temperament and aggressive nature they have special role to cause destruction. Our sages had a divine method to calculate their inauspiciousness. This method is known as “ Kantak-Shool”method. The word “Kantak” means “Thorn” and “Shool” means “a kind of sharp weapon”. To calculate the inauspiciousness first the position of Sun’s nakshatra to Mool nakshatra. This will be equation “(1)”. Now count the nakshatra occupied by Mars to moola. Treat this number as (2). As per rule the total of (1) and (2) is called “ Kantak-Shool”. The total we get will be considered as (3). Lastly count from the Moola nakshatra till the number denoted by equation number (3). The resultant nakshatra will be the “Kantak-shoola nakshatra”. This nakshatra is so dangerous that it destroys the significance of the planet occupying that nakshatra.
Suppose in a birth chart Sun is placed in Rohini nakshatra, and Mars is placed in Chitra nakshatra. Now start counting from Rohini till Moola, we get 16. In Next step count from Chitra till Moola, we get 6. The resultant figure would be 16+6=22. The 22nd nakshatra from the moola would be deadly one. Here it comes to be Hasta nakshatra. A planet occupied in Hasta nakshatra would loose its beneficiance.
It is believe that this is such a malefic yoga that there is no remedy for that.