I came by some graphs showing the declination for sun and moon (between angles of -30° and +30°). The graphs look very much like sine waves.
I googled a bit and read about what the declination is, and I found tools to look up the declination for a certain date. However, what I really haven't understood yet is, how to measure the declination. So if I would like to create such a graph during the next 365 days by hand, what exactly would I measure?