* Dual mode Sidereal Time display or Universal Time display. 
	* 24 hour display of Hours, Minutes and Seconds. 
	* 6 x 0.8" high LCD digits with good contrast in daylight.
	* Switchable red LED BACKLIGHT for use at night.
	* Microprocessor based with Quartz crystal accuracy. 
	* 12V DC operation with PP3 battery back up.
	* Time set (reasonably finger proof). 
	* Observatory style metronome 'PIPS', switchable.
	* Absolute accuracy available with CRYSTAL OVEN option.
        * Pricing

The Sidereal Clock model SC110 from AWR Technology is designed for Astronomers to keep track of 'Star Time'. It runs faster than Greenwich Mean Time by about 4 minutes a day to complete an extra 24 hours in one year. This rate matches that of the Sidereal Heavens and so the time, once set, will show the Right Ascension of the object passing the observer's Meridian (due South).

This display of Sidereal Time is useful in knowing what is in the sky at any time by reference to star atlases; for setting drive systems in Equatorial telescopes; and for use in calculations, typically for converting coordinates of stars to horizon coordinates so that an Alt-Azimuth telescope can be pointed directly at an object. It is also very easy to predict rising times of objects and useful in locating planets in the daytime.

The clock is designed to be left running permanently and so will require very little re-setting. The 12 volt DC power requirement makes it convenient to be powered anywhere, using a car battery for remote site operation or mains option for permanent installation. See "Getting Stable Oscillator Circuits" to read how we achieve the required atability. We take a lot of care over this process and test the temperature coefficient so it will perform within specs on every unit shipped.

GENERAL SPECIFICATIONS

Calibration accuracy   . . . . . +/- 0.2ppm at 20 deg C
Temperature stability  . . . . . +/- 30ppm over range -10 to 60 deg C 
Divergence between Sidereal and Universal time . . . .  1.89s per year
DC Input: 10V to 16V DC at less than 16mA. 
Battery back-up: PP3 alkaline type (NOT SUPPLIED) with 50 hours of use.
Size: 235 x 70 x 125mm 		Weight: 0.5kg 

EXPECTED VARIATIONS WHEN TEMPERATURE CHANGES from 20 to 0 deg C
	Standard clock		1 second per day
	OPTION 5		1 second in 4 days
	OPTION 7		1 second in 120 days

The time is set using the 'SET' key in conjunction with 'FAST' or 'SLOW'. The hours is set first, then the minutes. The seconds display is zeroed when the minute is incremented during set so to synchronise the time (using the telephone time service, for example) the minute counter must be advanced exactly on the minute pip. With practise the setting error can be made less than 0.2 seconds, and of course it can be checked at the next time check and re-done if necessary.

The metronome is available at any time by pressing the switch, pressing it again to turn it off. This will cause short beeps at every second with a longer beep at the minute. The start of the sound is always in synchronism with the UT clock.

The 16 page handbook accompanying the clock gives full operation and connection instructions and shows five ways of setting up Sidereal Time and using it in practise. This book is also available separately.

The clock as described requires an external power source of 12 Volts DC (a car battery or mains adapter is ideal) to maintain continuous operation. It also has a backup power operation facility using a PP3 battery (not supplied). Operation of the backlight increases the power consumption by 50% to reach the maximum figure quoted in the specifications. When the PP3 is near the end of its life the clock will start losing time.

OPTIONS

• OPT 1: Internal rechargeable NiCad battery instead of PP3 to allow for continuous availability of power. Useful if the clock relies on the PP3 power source frequently. Especially during transportation to remote observing sites. Allows at least 25 hours of use, always available.
• OPT 2: Electrical output of the 1 Hz metronome control signal. This output is an opto-coupled signal and can be connected to other equipment safely without interference. The opto-switch starts to conduct at the beginning of the second and lasts for 0.16 seconds or 0.48 seconds at the minute pulse. Connection is via 3.5mm Jack Socket on the rear panel. It is always in synchronism with the UT clock.
• OPT 3: Variable brightness backlight to allow setting according to the users conditions. Control on the rear panel.
• OPT 4: A mains adapter to provide 12V DC fed into the back of the clock. NOTE: We cannot supply this option to America or Canada.
• OPT 5: Improved temperature performance with a 5ppm crystal over the temperature range 0 deg C to 35 deg C. Reduces errors caused by fluctuating ambient temperatures by approx 4 times.
• OPT 6: Tape recorder output of the metronome signal. 800Hz signal of the pulse envelope, long or short, present all the time, always in synchronism with the UT clock.
• OPT 7: Crystal OVEN oscillator to maintain absolute accuracy less than 5 seconds over 6 months. It can be operated over -5 deg C to +35 deg C with an accuracy of 0.005ppm per degree C. The major sources of error are calibration and ageing of the crystal itself (approx 0.1ppm per month). Calibrated to +/- 0.05ppm. Recalibration is required to maintain accuracy. This option requires a maximum of 130mA supply from 12V DC. OPTION 1 is advised if power interruptions are not to upset the crystal oven.

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