A fine astrolabe by Muhammad Muqim, the celebrated astrolabist of Lahore,
composed of brass, this fine piece was made by Muhammad Muqïm, the third in line of the prolific instrument-making family of 17th-century Lahore. He was a prolific instrument-maker known by over 30 pieces, of which this is a typical production.
The throne is elegantly worked à jour. The scale around the rim is divided and labelled for each 6°, subdivided for each 10, clockwise four times 6°-90°.
The mater is engraved with a gazetteer in three rings giving longitudes and latitudes for 31+23+11=65 localities. The first entries in each ring (counter clockwise from the top) are Cairo 63°20' 30°20'; Ghazna 104°20' 33°35'; and Ajmer 111°5' 26°0'. Such gazetteers were common and some also gave values of the qibla, that is, the local direction to Mecca.
The rete is not as carefully executed as the rest of the instrument. It has a distinctive design including two upturned beehive frames below the ecliptic at the two intersections with the vertical diameter. There are about two dozen star-pointers, but for some stars it is not clear where the pointer is actually situated. Most of the pointers, but not all, are marked with dots.
On the plates the latitudes are marked together with the lengths of longest daylight in hours and minutes (h/m). The plates are marked in a variety of ways. All have altitude circles for each 60 (H). All have azimuth curves, either above (A+) or below the horizon (A-) or both (A1). All have curves for the seasonal hours (SH). Some have curves for the hours since sunrise (HSS), others also have curves for the hours before sunrise (HBS). To summarize:
22°, 13h21m: H, A-, SH, HSS, HBS -- 25°, 13h: H, A+, SH, HSS, HBS -- 27°, 13h43m: H, A-, SH, HSS, HBS -- 30°, 13h58m: H, A-, SH, HSS, HBS -- 32°, 14h8m: H, A-, SH, HSS -- 36°, 14h32m: H. A+, SH, HSS -- 40°, 14h: H, A1, SH, HSS
One side of a plate is marked with altitude curves for each 6° and azimuth curves for each 100 for latitude ca. 66°30', the Arctic Circle. This bears no inscriptions, but such plates serve to facilitate conversion between ecliptic coordinates (longitude and latitude) and equatorial coordinates (right ascension and declination).
Another is marked with four sets of half horizons for each 8° from 6° to 62°, 80 to 64°, 10° to 66° and 12° to 60°. This is for operations involving only the horizon, such as length of daylight or the arc of visibility for a star.
A more remarkable, and less usual plate bears two sets of altitude circles for each 6° serving latitudes 0° and 18°, although neither latitude is stated.
Such a variety of plates constituted a kind of astronomer's delight.
The upper rim of the back bears two altitude scales divided for each 6° and subdivided for each 1°. In the upper left quadrant there is a set of equi-spaced parallels for each 2 units to 60, for trigonometric calculations. In the upper right there is a solar quadrant with two curves displaying the solar altitude at midday for latitudes 27° and 32°. Below the horizontal diameter there is a double shadow quadrant for bases 12 (asäb'i, on the left) and 7 (aqdäm, on the right), labelled as digits and feet. Around the lower rim are scales for the same cotangent (horizontal) and tangent (vertical) functions. (The units 12 and 7 were standard.) Inside these are some semi-circular scales showing the relationship of the 28 lunar mansions to the 12 zodiacal signs. And inside these is the inscription:
"The work of Muhammad Muqïm ibn 'Ïsä ibn Iläh-däd Asturläbï Humayünï".
An attempt has been made to insert the word Lähürï, "from Lahore", near the hole at the centre. The date is engraved upside down under the shadow squares: "1047 Hijra", that is, 1637/38.
Images of the plates available on request