Better than a stopwatch?

From: michael.waterman@gecm.com
Date: Fri Mar 10 2000 - 06:12:26 PST

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    If you are determined to time with stopwatches, read no further.
    
    When I started serious observing many years ago I used a 
    mechanical stopwatch, and later used a digital wristwatch with
    stopwatch facilities, and also electronic stopwatches. In 1983 I 
    got a (non-PC) computer, this had an internal clock, but no battery 
    backup. In 1986 I attached a separate clock to the computer, and soon 
    wrote a program so I could use it to record satellite times. When I 
    later got a PC, an alternative version of the program was written to 
    use the PC clock. The old clock drifts less with time, and is 
    normally used.
    
    I now rarely use a stopwatch.
    
    From seesat contributions I guess that most observers making
    accurate observations use stopwatches.
    
    Summary of my computerised system.
    
    The computer games card (or equivalent) has 2 pins called "Fire" or
    something like that. On my PC they were on a 25-pin D socket round
    the back. When a Fire pin is connected to the earth pin the event 
    can be observed. In QBASIC it is observed with the STRIG function. 
    Other languages will presumably have equivalent functions. 
    The function can either be read repeatedly in a loop, or made to 
    cause an interrupt.
    
    These pins and the earth are connected via a cable to the observer.
    In practice there is a short cable from the PC to a wall socket,
    a fixed cable from the wall socket to various other sockets, some
    indoors near windows, and two outdoors. I use 4-wire telephone
    cable and 5-pin DIN sockets & plugs. A box has one button on it,
    and a short cable with a another hand-held button. A long cable
    comes from the box and plugs into a socket. The computer appends
    observations to a file, so no observations are lost due to power
    interruptions (not happened yet).
    
    Disadvantages of PC clock:
        You are tied to a computer.
        You need to make the equipment.
    
    Advantages:
        You can make a virtually unlimited number of observations.
        Less trouble : the data goes straight into the computer.
        There is no risk of typos in recording times.
        There is no risk of pressing the wrong button, and losing
            your data.
        There is no danger from low batteries, or its mechanical
            equivalent.
    
    The box also has a red LED light, and a small speaker. 
    The speaker is in parallel with the computer speaker. It emits pips 
    each second, normally short, longer pips each 10s, and 1 to 5 long 
    pips on a minute.
    
     The pips mean that you dont have to stop looking at the sky to know 
    the time.
    It also reassures you that the system is still working.
    
    Different tone pips happen if a button is pressed, so you know your
    observation has been recorded.
    
    The second button can be used as a spare, or to distinguish position
    observations from flash timings. For flashes, you just press the
    button on several (often 20 or more) maxima, and the program can 
    determine the flash period. No problems about remembering how many
    flashes there were. The buttons are identified as 1 and 2 in the
    recorded file.
    
    The same buttons are used for me to record audio radio time signals, 
    so the observation times can be adjusted to UT.
    
    To simplify processing, if I press a button for >1sec, the 
    recorded button numbers are increased by 2. This makes it easy
    to separate time signals, positions and flashes.
    
    Actually I have 4 boxes, one close to the PC and radio, one for
    outside use, one by the most commnonly used window, and a spare.
    
    Possible improvements:
        Use 5-wire cable instead of 4. This saves having to use the same
            wire for light-power and sound.
        Use IR or radio link: saves tripping over cables on the ground, 
            and gives greater range. Anyone tried this?
        Use electronics to record radio time signals, instead of my ear
            and finger.
    
    Perhaps a seesater has suggestions or improvements.
     
    Mike Waterman      michael.waterman@gecm.com
    Site Yateley = COSPAR 2115 =  51.3286N  0.7950W  75m.
    
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