罕見的 Nocturlabium(日晷)，365 mm，約 1550
A collection of 5 time-measurement instruments
A rare Nocturlabium (sideral clock), 365 mm, circa 1550
A richly ornamented iron instrument
Recto: Circles for date with zodiac-symbols, 2x 12 h. Turnable plate with two arms to indicate the stars α and β of the great (Uma)- and β of the little (Umi) bear. Scale 0- 291/2 for the moon age to compute the time of high tide according to a distinguished harbour. Inner circle again 2 x 12 h.
Verso: Two circular Tables according to the angles of α /β Uma or β Umi are indicating the vertical deviation of α Umi from the exact north pole. The maximum value is an indication for the age of the instrument. When e.g. with an astrolabe the high of β Umi is taken these values may lead to the correct latitude of the ships position.
Handling: After setting the date α of the little bear is aimed through the hole and the alhidade is positioned to α /β Uma or β Umi. On the time-scale the time can read. In the northern hemisphere the two bears are always visible, therefore the instrument can be used all over the year. The condition of the instrument is very good.