It gives accuracy of one minute of an arc or 30 seconds of an arc. Available in Brass and Stainless Steel scale in both the sizes of 15.0 cm (6") and 17.5 cm (7") of protected circle.
eBay
Little Garden Spectrometer, DIY Spectrometer, Measure LED, Laser, Absorption Spectrum, Based on Theremino
Aliexpress UK
It gives accuracy of one minute of an arc or 30 seconds of an arc. Available in Brass and Stainless Steel scale in both the sizes of 15.0 cm (6") and 17.5 cm (7") of protected circle.
eBay
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