What do you mean by "exposure" and "superposition" in astronomy?

In astronomy, "exposure" and "superposition" have the following meanings:

"Exposure" refers to the process of imaging photosensitive film or photographic paper under certain illumination conditions, or the process of making light pass through a lens to form imaging light, enter a black box and reach the photosensitive film, so that the film emulsion produces a latent image under the photochemical action. In this process, factors such as light intensity, wavelength and irradiation time received by photosensitive film or printing paper will affect the brightness, color and details of the image.

In astronomy, "superposition" usually refers to the synthesis or superposition of observation data at different times, different angles or different devices in order to obtain more accurate and comprehensive information on the structure of celestial bodies or the universe. For example, by superimposing astronomical images with different wavelengths, we can better understand the nature and structure of celestial bodies; By superposing the observation data of multiple telescopes, a higher resolution image can be obtained.

The superposition principle is also widely used in physics and engineering. It can be used to explain the propagation phenomena of various waves such as acoustic waves and electromagnetic waves. In signal processing, image processing and other fields, the superposition principle is also widely used, such as image enhancement, noise suppression and so on.