Introduction to Solar Observing	Course Overview	Course Syllabus	Course Schedule
		Index of Course Sessions

Instruments for Spectral Studies

An entrance slit in front of a light source allows light to filter through to a collimating lens, which forms the light into parallel rays. The rays are then refracted by the prism and focused by the camera lens. A ray of violet light is brought to focus; the ray is imaged as a line at the focal surface. Red light from the slit is also imaged but, because of its different refractive properties, it images at the other end of the focal surface.

Figure 22 One possible design for a spectrograph utilizing a prism.

The spectroscope design in Figure 23 below employs a slit in the barrier allows a narrow beam of light to pass. The beam passes through a prism and is split into its component colors. A lens then focuses the light into a sharp image that is either projected onto a screen, as shown here, or analyzed as it is passed through a detector.

Figure 23 Simple spectroscope using a prism.