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    Re: Longitude by calculator -theodolite
    From: Greg Rudzinski
    Date: 2013 Jul 1, 21:04 -0700

    Bruce,

    I like the Ultrak 440 model stopwatch. Features splits, 24 hour time/date, alarm, count down alarm, and takes a lithium 2032 battery. At $25 it's hard to beat.

    Greg Rudzinski


    Re: Longitude by calculator -theodolite
    From: Bruce J. Pennino
    Date: 2013 Jul 1, 22:53 -0400
    Hello Paul, Antoine, and All:

    The stop watch idea is a good one, and I'll look for one. But I like just reading my digital watch; simple. Someone please recommend a stop watch of the variety described by Paul. It would make tabulating data easier!

    I want to take data in some daylight because I can see the cross hairs easily without using a flashlight. Adjusting the theodolite, reading time and recording data is complicated enough. The moon is big, convenient and just easy.

    Because my theodolite body has a low height (a short pivot, hard to describe), I must select a celestial body at relatively small Hs (large zenith angle). Say it another way, I can't get my eye to instrument if I want to sight a large Hs. My maximum Hs is 30-35 degrees. I read the angle to nearest second, but the merest touch moves the hairline. So the value is realistically only good to a second or so. Deflection of the vertical is one of those errors that I just "lump into small errors difficult to quantify". That is why my accuracy as perceived by me can't be plus or minus three seconds. Any measurement where I am within 3 seconds , Hc-Ho, is just plain luck or happenstance. Averaging balances various errors, but good luck is difficult to trump. There are just too many embedded places where errors can result. I now believe I can probably, on average, measure a Hs to within 6 seconds, but I said 12 seconds just to give myself " some slack" and have confidence in the results.

    For my measurements, I think recording normal weather or water conditions does not add much on any practical basis. Unusual conditions should be recorded. When I make dip measurements, I do record weather and water conditions.Antoine, when I did the moon celestial measurements, I did not bother to record any conditions. There was no significant wind ; it was a pleasant New England evening and I was standing in shirt sleeves 65-70 F. Normal air pressure conditions.

    Thank you for data analysis. For the past three days we have had rain, fog, haze and mist. I'll try to sight some stars in near future and analyze; Hc-Ho.

    Best regards,
    Bruce

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