Sullam al-Nayyirain is one of several books written by KH. Muhammad Mansur el-Batawi. This book is famous among experts who study hisab and astronomy. This classic book is still widely used by the hisab scholars in determining the beginning of the Islamic Calendar (qomariyah). The method is based on Geocentric theory, which states that Earth is the centre of the solar system. There are three chapters in this book:
- How to use hisab system in calculating when the ijtima happened (conjunction) between the Moon and the Sun.
- The treatises about the calculation of lunar eclipse.
- The treatises about the calculation of solar eclipses.
Since the Kiai Yahya period, Pondok Gading has taught and practised the book of Sullam al-Nayyirain. Therefore, Pondok Gading has has Lajnah Falakiyah Pondok Pesantren Miftahul Huda (PPMH). Lajnah Falakiyah is the institution that specifically has a management to determine the beginning of the Islamic Calendar (Qomariyah).
That is one of the greatest heritage from the legendary Kiai in Pondok Gading. That inheritance still exists until now. This is because there are so many pesantren who also adopt the hisab method in Pondok Gading.
Interestingly, although many pesantren adopted the hisab technique, Pondok Gading’s calculation results were always more precise, even though the methods were the same and sourced from the same book. It was also acknowledged by KH Muhammad Baidlowi Muslich, one of the masters of Pondok Gading. “That’s because we are thorough and pay attention to the techniques for generations,” KH Muhammad Baidlowi said.
Because of this reason, the results of Pondok Gading hisab always become the main reference in the process of making the Islamic calendar to determine the Idul Fitri.