One of the most common sky glow meas urements is the luminance or radiance distri bution. The characteristics of the instruments used are important components in photomet ric measurements of luminance and thus play a key role in analysing sky glow. Many photo- metric instruments have been primarily designed for use in different conditions to those found in at night and, hence, lack the sensitivity to perform sky glow measurements. To study specific luminance distributions, investigators have applied an assortment of devices such as CCD (charge-coupled device) cameras, astronomical cameras, spectrometers and luminance meters.
The past 30 years have seen rapid advances in the field of electronics. One of the most significant events of the 1970s was the inven tion of the microprocessor. 20 This device has been used as the central system in consoli dated control apparatus supporting integra tion techniques, and increasing the study of the virtual memory and machine language. Subsequently, microcontrollers have been developed containing a similar structure as the CPU (central processing unit), with a memory RAM (random-access memory) and ROM (read-only memory), and input and output elements. These microcontrollers can perform a wide range of logical and sequen tial operations, and are extremely versatile for numerous applications.
The objective of this study is to develop and construct a microcontroller-based system with the aim of improving the measurement possibilities offered by digital single-lens reflex (DSLR) cameras. The system is an inexpensive reliable platform that is easy to prepare and control, and therefore forms the basis of the spatial and temporal modelling of nocturnal ambient lighting. The system has been configured to accurately quantify sky glow levels by automating the measurement of the artificial sky luminance, reducing the human interface, and avoiding the thermal dependence of the camera sensor. The flexi bility of the system can generate a wide range of measurement capabilities by using an automated data acquisition procedure. The system allows one to obtain calibrated and continuous data. This fact offers an advan tage for researchers who, for any reason, cannot perform in situ measurements over a long time.