For 14 CFR part 61 operations, the term night refers to 1 hour  after sunset and ending 1 hour before sunrise as 14 CFR part  61 explains that between those hours no person may act as  pilot in command (PIC) of an aircraft carrying passengers  unless within the preceding 90 days that person has made at  least three takeoffs and three landings to a full stop during  that night period.  Night flying operations should not be encouraged or  attempted except by certificated pilots with knowledge of  and experience in the topics discussed in this chapter. Generally, most pilots are poorly informed about night vision.  Human eyes never function as effectively at night as the eyes  of animals with nocturnal habits, but if humans learn how  to use their eyes correctly and know their limitations, night  vision can be improved significantly.  The function of the cones is to detect color, details, and  faraway objects. The rods function when something is seen  out of the corner of the eye or peripheral vision. They detect  objects, particularly those that are moving, but do not give  detail or color—only shades of gray. Both the cones and the  rods are used for vision during daylight. Although there is not a clear-cut division of function, the rods  make night vision possible. The rods and cones function in  daylight and in moonlight, but in the absence of normal light,  the process of night vision is placed almost entirely on the rods.  The rods are distributed in a band around the cones and do not  lie directly behind the pupils, which makes off-center viewing  (looking to one side of an object) important during night flight.  During daylight, an object can be seen best by looking directly  at it, but at night there is a blind spot in the center of the field  of vision, the night blind spot. If an object is in this area, it  may not be seen. The size of this blind spot increases as the  distance between the eye and the object increases as illustrated  in  Figure 10-1 . Therefore, the night blind spot can hide  The eye’s adaptation to darkness is another important aspect  of night vision. When a dark room is entered, it is difficult to  see anything until the eyes become adjusted to the darkness.  Almost everyone experiences this when entering a darkened  movie theater. In this process, the pupils of the eyes first  larger objects as the distance between the pilot and an object  increases. Use of a scanning procedure to permit off-center  viewing of the object is more effective. Consciously practice  this scanning procedure to improve night vision. 10-2 Night Vision Figure 10-1.  Rods and cones. Area of best night vision Area of best night vision Night blind spot Area of best day vision Rods for • Gray Peripheral • Day and night Cones for • Color Detail • Day eye  The brain and eyes act as a team for a person to see well;  both must be used effectively. Due to the physiology of  the eye, limitations on sight are experienced in low light  conditions, such as at night. To see at night, the eyes are used  differently than during the day. Therefore, it is important  to understand the eye’s construction and how the eye is  affected by darkness. Innumerable light-sensitive nerves  called “cones” and “rods” are located at the back of the  or retina, a layer upon which all images are focused. These  nerves connect to the cells of the optic nerve, which transmits  messages directly to the brain. The cones are located in the  center of the retina, and the rods are concentrated in a ring  around the cones.  [Figure 10-1]