The Five-foot Spectroheliograph of the Mount Wilson Solar Observatory (camera lens, camera slit and plate carrier in section).
It is evident that by the use of a spectroheliograph of sufficiently high dispersion, photographs may be taken of vapours in the sun represented by lines narrower than those of calcium and hydrogen.
Such work has been in progress both at Mount Wilson and at Meudon, and the erection of a spectroheliograph of 75 ft.
The calcium flocculi, on account of the brilliant reversals of the H and K lines to which they give rise, and the protection to the plate afforded by the diffuse dark bands in which these bright lines occur, are easily photographed with a spectroheliograph of low dispersion.
A spectroheliograph which gives excellent results with the lines of calcium, hydrogen and iron is shown in the figure.
An electric motor, belted to a screw (1 or 1') connected with the spectroheliograph, is then started.'
The screw moves the spectroheliograph at a perfectly uniform rate across the fixed solar image.
The spectroheliograph, originally designed for photographing the solar prominences, disclosed in its first application at the Kenwood Observatory (Chicago, 1892) a new and unexplored region of the sun's atmosphere.
The first photographs of the sun in hydrogen light were made with the spectroheliograph in 1903.
For details of the coelostat applied to the Snow telescope - the most perfect installation for spectroheliograph and bolometer work yet erected - see The Study of Stellar Evolution by Prof. G.
He invented the spectroheliograph first used in 1892 for photographing solar prominences and won an international reputation for his solar and stellar spectroscopic work.
Hale devised on the same principle the " spectroheliograph," an instrument by which the sun's disk can be photographed in calcium-light by imparting a rapid movement to its image relatively to the sensitive plate; and the method has proved in many ways fruitful.
SPECTROHELIOGRAPH, an instrument for photographing the sun with monochromatic light.