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Hawaiian Astronomical Society

Constellations: Horologium -- When Clocks became Useful


Horologium Oscillatorium was named in honor of Christiaan Huygens (1629-1695) by Nicolas-Louis de Lacaille. Amateur astronomers remember Huygens as the inventor of those horrible little eyepieces supplied with every 600x, 60mm department store trash scope. In fact, these eyepieces perform well at longer f ratios, and are genuinely achromatic. Huygens also claimed credit for describing light as a wave, and recognized that the twin lumps Galileo saw protruding from Saturn was actually a ring. Oh yes, he also invented the pendulum clock, from which this constellation derives its name. Educated at Leiden and Breda (he studied law and mathematics), he spent his most productive years in the Hague, before moving to Paris (1666).

A couple of final comments: The pendulum clock allowed much more accurate time keeping. A pendulum one meter long has a beat (one half swing) of almost exactly one second. Also, Huygens wrote one of the earliest discussions of extraterrestrial life called Cosmotheoros.


Each map can be clicked on to produce a 909x1199 version of it. They sport red labels, which look good on screen, but which disappear when used with red flashlights. Each map, therefore has a second link to a map better suited for printing in a graphics program, and using in the field. While the maps are quite large, they are all about 25-55k, and so are easy to view at today's modem speeds. The first map is a wide area view of the constellation, suitable for naked eye browsing. The next views are binocular width, showing stars to mag. 10, and labeling deepsky objects to magnitude 12.

Interactive, wide area map of Horologium

Map thumbnail

Click the map for a 916x1200 version of the above. Click here for a map better suited for use in the field.

Northern Horologium

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This a more detailed view of the constellation. The map displays stars to magnitude 10, and deepsky objects to magnitude 12. Click here for a map better suited for use in the field.

Southern Section

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Click here for a map better suited for use in the field.


Image thumbnail 57k JPEG NGC1512 is a spiral galaxy located in northeastern Horologium, 2.1° WSW of Alpha Horologii. Dreyer describes it as having an extremely faint ring. The remainder is bright (mag. 11), quite large (8.9'x5.6'), round, with a brighter middle. The ring Dreyer describes is an active star forming region, and is visible only in larger amateur instruments.

NGC1510 sits 5' to the south-west. Dreyer describes this small (1.3'x0.7'), faint (mag. 13.5) companion to NGC1512 as showing very gradually much brightening toward the middle. Image from the Digital Sky Survey.
Map Printable Map

Image thumbnail 19k JPEG NGC1433 is a barred spiral galaxy located in east-central Horologium. It forms the right angle of a triangle consisting of itself, Alpha Horologii, and Alpha Doradus. Dreyer describes it as very bright (mag. 10.8), large (6.4'x5.8'), moderately extended to the west, with a very abruptly very much brighter middle. Indeed, the center looks like a 10th magnitude star. The star forming ring, so prominent in photographs, is not visible in amateur telescopes. Image from the Digital Sky Survey, and given additional processing.
Map Printable Map

Image thumbnail 47k JPEG NGC1261 (Bennett 11, Caldwell 87) is a globular cluster located in west-central Horologium, 4.5° east of the mag. 5.2 Zeta Horologii. Dreyer describes it as bright (mag. 8.4), large (6.9'), round, and very resolvable (in a 12" telescope).
Map Printable Map


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