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  • How to build a simple Twilight Photometer

    The gain equals the feedback resistor's resistance. A 10-gig resistor provides 10 gigs of gain. Important: the resistor must be kept very clean to avoid a reduction in resistance that can be caused by dust and fingerprints. This affects only the signal amplitude and not the measured elevation of aerosol layers.

    Thanks for adding the acknowledgment.Forrest M. Mims III

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  • How to build a simple Twilight Photometer

    In view of the considerable time I spent developing thisproject for my science column in MAKE magazine, it would have been good if theauthor had fully acknowledged his source for the circuit in this project rather than simply suggesting it was a"Build example." My fully detailed, 2-part column in MAKE that he used as his sourceis free at: http://makezine.com/projects/twilight-photometer/Forrest M. Mims IIIhttp://www.forrestmims.org

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