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Lu Abel wrote:
> Not to mention that that many digits means we can locate the sun's 
> center to within 0.00015 arc-seconds.   I'm a navigator, not an 
> astronomer, but that seems rather precise for a pulsating body....
>
> Lu
>
> frankreed@HistoricalAtlas.com wrote:
>   
>> "11 February 2009, 05:28:32.5 GMT, the equation of time being 14 minutes 
>> and 13.78019 seconds."
>>
>> Thanks. How many of those digits past the decimal point do you think we can trust?
>>
>> -FER
>>
>>
>>     
I knew these reactions were coming and to be honest: I would not even 
trust the first digit, as I never tested the formula's I found to this 
level and neither were they properly annotated. The reason that I gave 
so many digits was the simple fact that even to change that last digit 
takes almost 15 minutes. One digit less (so four digits) means a 
time-span of about a hour, making it more difficult to give you a proper 
date and time of SSD. Only one digit corresponds to a time span of 
roughly 20 hours.

I did test the software using sun shots and compared the results with a 
known azimuth. From these observations it at least became apparent that 
the equation of time is accurate to the second and possibly even to a 
tenth. It is however extremely difficult to test beyond that scale as 
taking sun shots is done manually by observation. In addition to that I 
had to set my clock manually as well. The errors in the sun shots might 
cancel out on average when taking multiple shots (tapping the touch 
screen of my cell phone that runs the application while keeping focused 
on the sun through the theodolite), but the error in my clock will not 
as I cannot set the time on average using multiple observations from a 
reference clock. It is for this same reason that normally my application 
does not accept input beyond 0.1 seconds and does not produce results 
beyond that same resolution. I temporarily modified it to 5 digits to 
make the calculations in NavList 7301 possible.

Nicol�s


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