The amplification of the sensor’s signal, set as ISO on a camera. Raising the gain does not capture more light: it makes the image brighter but reduces dynamic range. A medium to high gain lowers read noise, which helps with short exposures and planetary work.
Related terms
- Exposure
How long the sensor collects light for one frame. For deep sky, take many exposures of 30 s to a few minutes and stack them; for planets, exposures of a few milliseconds freeze the seeing. Without tracking, exposure is limited by the NPF rule.
- Sensor
The electronic chip in a camera or astronomy camera, made of millions of pixels that turn light into a signal. Its key figures are the pixel size (in micrometres), the sensor dimensions and its noise. Astronomy cameras are often cooled to reduce thermal noise.
- Signal-to-noise ratio
The strength of the useful signal (the object’s light) compared with the random fluctuations that make the image grainy. It is the measure of an astrophoto’s quality. It grows as the square root of total exposure time: four times as many frames give an image half as noisy.
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