In the golden period of monastic life, after the construction work carried out in the reign of João III, the daily life of the religious community at the Convent of Christ still depended very much sunlight. It is thus only logical that the Scriptorium, the room dedicated to writing and reading, faced south and had large windows that provided the necessary daylight.
The friars' cells also had a window that allowed them to read. The light generally hit the left side of the room, which was where the friars had a stone bench and a small niche that served as a shelf for books.
Generally speaking all the rooms at the convent were well served with natural lighting, and in many cases the window and door spans were positioned obliquely so as to better catch the sunlight.
The windows in the corridors and church are tall, and there were skylights in cupolas and the crosses of vaulted ceilings. In more domestic quarters, the size of the windows was understandably smaller.
However, monastic life did not end at sundown. For this reason, in the Convent of Christ, and other similar monastic spaces, there was no lack of torches, candle holders and other lighting equipment. Olive oil or wax burning lamps and lanterns were used in both everyday life and religious acts.
The friars and other co-habitants of the monastery used individual lamps to move around the Convent at night. At the Philippian gatehouse there is still a storage space for lamps that were handed out to outsiders who arrived at the Convent after nightfall.
For parts of the Convent that had permanent night-time lighting, maintenance of the light sources was guaranteed by a friar specifically charged with that task.
Stargazing was also a common activity at night, which is why there are still visible remains of a clock tower that served as an observatory as well.