Sidereal clocks and visibility calculators

Sidereal clocks

The spreadsheet SiderealClock calculates the sidereal time in London, and at the sites of the telescopes in Hawaii and Australia. It also shows Universal Time (UT or GMT) and the ordinay local time at the three sites.

Sidereal clocks are used in observatories because they make it easy to predict when an object is visible if itsright ascension (RA) is known - this is analagous to longitude on Earth.

You can choose to set the clocks for a particular date and time or to set them to the current date and time.

Download the clocks by by right-clicking the following link and choosing to Save target to a convenient location on your hard disc.

Download sidereal clocks

Visibility calculator

The spreadsheet visibility calculates which objects in a list of possible targets are visible in every half hour time slot on a particular day. It incorporates the sidereal clocks referred to above.

You can choose to set it for a particular date and time (if you are planning ahead) or to set it to the current date and time.

You can enter you own list of up to 200 objects if you know their RA and Dec coordinates.

The calculator also gives precise times for rising, setting, reaching a given altitude (usually 30 degrees), crossing the meridian, sinking below the given altitude, and setting.

Download the visibility calculator by right-clicking the following link and choosing to Save target to your hard disc:

Download visibility calculator

Richard Beare    22nd July, 2004