Astronomical Detectors & Spectrographs: Structures & Vocabulary

Modern astronomy depends on detectors that count or measure incoming radiation and instruments that separate that radiation by wavelength. CCD and CMOS sensors convert photons into electronic signals, while spectrographs disperse light so wavelength-dependent information can be measured.

An imaging detector contains pixels with finite quantum efficiency, read noise, dark current, full-well capacity, and gain. A spectrograph commonly includes an entrance slit or fiber, collimating optics, a prism or diffraction grating, camera optics, and a detector.

Calibration frames measure detector bias, dark current, pixel sensitivity, and wavelength mapping. Laboratory lamps with known spectral lines establish the relationship between detector position and wavelength.

Optical CCD and CMOS arrays consist of pixels that accumulate photo-generated charge or equivalent electronic signals. Spectrographs add an entrance slit or fiber, collimating optics, a grating or prism, camera optics, and a detector. Resolution depends on slit width, disperser properties, optical geometry, and sampling. Infrared, ultraviolet, X-ray, and radio instruments use different detector technologies because photon energy and interaction mechanisms change across the spectrum.