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Re: Long Prisms for homemade spectrometer



One doesn't simply pass sunlight through a prism to demonstrate the
Fraunhofer absorption spectrum of the Sun. That works for Newton's
demonstration of the phenomenon of colors, but for the narrow lines
one needs lenses to collimate and focus the radiation, and an
accurately aligned entrance slit as long as the desired spectrum is

However, a cheap grating and slit brings out the lines just fine...

I see faint lines in sunlight and cloud reflected sunlight through my
el-cheepo $20 Project STAR Diffraction grating spectroscope.
https://www.mailordercentral.com/aspsky/prodinfo.asp?number=OA%20160&variation=&aitem=8&mitem=9
is where to see the device.

I have been blissfully assuming these lines are fraunhofer absorption lines,
an interpretation the STAR spectrometer folk have fostered in the
accompanying literature that comes with the device. If these are NOT
Fraunhofer absorption lines, I'd like to know what they are.

Otherwise, I assume the much greater dispersion of the grating overcomes the
need for a slit any better than that provided with my toy...

Dan M

Dan MacIsaac, Assistant Professor of Physics and Astronomy, Northern AZ Univ
danmac@nau.edu http://purcell.phy.nau.edu PHYS-L list owner