Abstract

Microprocessor Devices for Timing Astronomical Events

Janusz Wiland, Pawel Gawronski
Presented by A. Wrembel

Auf der Basis von DCF-77 Zeitsignalen wurden zwei mikrorechnergesteuerte Geräte entwickelt.
Die Einblendung von Zeitsignalen in Videosignale wird flexibel realisiert und gestattet die zusätzliche Angabe der Temperatur und von drei Textzeilen. Dabei stehen mehrere Darstellungsarten zur Verfügung.
Die Registrierung von Zeitsignalen durch bis zu acht unabhängige Beobachter mit der Genauigkeit von 0.01 sec erlaubt zur Zeit die Speicherung von 21 Momenten.
Eine Kopplung an einen GPS-Empfänger ist für beide Geräte geplant.

In Europe the precise time signals DCF-77 are easily accessible. On this basis, we have built two devices - the inserter and the registrator - with the purpose to perform timing of astronomical events precisely. Both devices are controlled by an 8-byte processor of the MCS51 class.

The procedure of decoding the signals is identical for both devices. The inert quartz clock synchronizes its time every second according to the DCF radio-signals. In the case of fading of the signals, the re-synchronization takes place after receiving of five consecutive correct second-signals. It should be admitted that systematic delay in relation to the standard radio-signals is observed and it is caused by the internal processing the signals by electronic systems. However, both the devices were equipped with a software introducing the necessary correction of time automatically and thus the final running of each device is perfectly consistent with the pattern radio-signals. After one minute time of receiving the correct radio-signals, the current date and time is set.

The Inserter

The inserter is a device used for putting the precise information about the time into the video-signal. As usually, the device is being set between the camera and the video-recorder. Apart from the date and the time, the inserter also shows the time-spot of the DCF signals and the current temperature on the monitor screen. Additionally, the user can introduce three lines of his own text, 20 characters all (ASCII, Greek letters and astronomical symbols). The characters can be displayed using various options : with a background or without it, with a white or black background, with a white or black colour. The text can be shifted vertically to any place onto the screen.

There are four options of displaying the information:

• three lines - date, time, temperature + text
• three lines - date, time and temperature only
• one line - date, time, temperature
• no information on the screen

The additional markers for tenths and hundredths of a second could also be added which allows for more precise reading out the time of recorded events. The inserter contains the amplifier of the video-signal, with the possible amplification of the voltage in the range of 1-2 times. The signal from the amplifier is mixed together with the signal from the generator of characters. Next, the signal passes through the limiter of the video-signal amplitude. The limiter cuts off the signal from the white level side. Thus, it eliminates the possibility of over-controlling the input video-signal and guarantees the proper setting of the system of automatic control of amplification.

The system makes it possible to intensify images of faint objects as well as to equalize the brightness to the level of the most bright objects (the Moon, the planets). By such an amplification, the image of the Moon represents the uniform, white disk without any features on its surface. In the future, we plan to couple the inserter with a GPS instrument, too.

The Registrator

The Microprocessor Registrator of Time (MRT) makes it possible to store in the memory moments of key pressing with the exactness of 0.01 sec. Eight observers using eight independent keys can work simultaneously. At present, it is possible to record 21 moments in the memory. When the key is pressed, the processor memorizes the current time and so called state-of-the key byte, that determines the assignation of the time to the proper key. If all of eight observers would press their keys at the same moment (although is less probable), only one moment would be stored.

In the future, we plan to develop the recording memory up to the capability of 250 moments as well as to build-in the interface for data transmission into the PC memory. Also, the registrator should receive the coupling with a GPS instrument.

Some further details and examples are also presented on our poster.

Janusz Wiland, Polish Association of Amateur Astronomers (PAAS)
Address: ul. Pasteura 4/6 m.57, Warsaw 02-093, Poland E-Mail: jawil@hend.com.pl, gapawel@free.com.pl
Telephone: +48 22 8229756

Artur Wrembel, Filharmonia, ul. Libelta 16, Bydgoszcz 85-080, Poland
E-Mail: krzgrzel@friko2.onet.pl Telephone: +48 52 604229301

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