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Before Hale built the SHS he built the SHG or spectroheliograph which I believe in some configurations did scan the image by turning the drive off. Other models by him, and Deslandres in France, scanned with a moving slit.

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Try ATM - Scientific American 1933; p180-214; Solar research for amateurs/ Hale's spectrohelio-scope/graph detailed drawings/photos -if dated by today's standards.

My spectrohelioscope had a fl of 900mm and used a single large lens segmented for both primary OG imaging the sun and auto-collimator [eg spectroscope] with 600 l/mm grating ruled by Brian Manning showing the idea/article at http://www.astroman.fsnet.co.uk/optics.htm

I recently sold the grating for a new SHS project.