I learned this from Pandit Sanjay Rath. He is simply the most brilliant astrologers in the world!
D27 is one of the most important divisional charts. It shows our strength and protection. The significator of this chart is Mangal (Mars) and his nature is to protect us. The D30 chart on the other hand shows our weaknesses and the negatives and the significator is Shani (Saturn).
When you divide the Rashi (sign) into 27 parts each part maps into a nakshatra. That is why if you see the Deities of Divisional charts for D27, they are the nakshatra deities.
The D27 chart Maps into the 3rd house and the D30 chart maps into the 6th house.
The D27 chart wants to protect us from all the negativity and pass on the good results. So if the D27 chart is very strong, the negative experiences could be very less.
The first part of the Sign maps into Ashwini nakshatra and the 27th part of the sign maps into Revati Nakshatra. So for example, if your Ascendant is in the 13th division of the d27 chart, then it maps into Hasta Nakshatra.
So if you read your chart based on this mapping it gives you deeper clues as to how your life is influenced by the Nakshatras. For example if Jupiter maps to Pushya nakshatra in the d27 chart and if your natal moon is in Pushya Nakshatra then the moon is heavily influenced by Jupiter. If 2 or more planets have a common mapping then they have a shared agenda.
For example, if you have your Saturn in the 13th division of the d27 chart, it maps into Hasta Nakshatra. Now check if you have any planets in Hasta nakshatra in your D1 chart. It is best to avoid the days when Moon transits Hasta nakshatra and you may also notice that people with prominent planets in this Nakshatra could cause some unhappiness for you.
Note – Make sure to choose the D27 chart from this page.
You will see the Nakshatra mapping within brackets next to the sign.