Pete Swanstrom wrote:
> I do still have one big question that I wish to resolve, which
> pertains
> to my analemmic equatorial sundial. The question is, how long will it
> be
> before the changing analemma renders my current analemmic gnomon
> inaccurate? (Say until either the date positions on the gnomon have
> shifted by 1/4 day or more, or the EoT for some date has changed by
> over
> 15 seconds.)
Pete,
Below are some data that may help you, the calculation date is
Jan 1 Noon UT, EoT values are in the form TA-TM. The discussion to date
has been more about the variation of our orbit and Earth's alignment
within, however all these events need to be related to a calendar and
since there is not a even multiple of days in our orbital period I think
you can see how the EoT becomes unsynced. Note that after twenty years,
which falls on a four year boundary from the start, the delta is 1.3
secs.
I look at including an Analemma on a dial as a must, if only to
confuse future generations and thereby inducing them to explore it
further. However, as many on this list have pointed out, you can never
go wrong with solar time.
Regards,
Luke Coletti
Column 1: day of year, Column 2: year, Column 3: days in year
Column 4: days from J2000, Column 5: Solar Day Length, secs
Column 6: EoT, secs, Column 7: EoT delta, secs
1 2000 366 +0.0 -28.5750 -198.0059 +0.000000
1 2001 365 +366.0 -28.3493 -219.3062 -21.300274
1 2002 365 +731.0 -28.4230 -212.3139 -14.307972
1 2003 365 +1096.0 -28.4950 -205.3031 -7.297152
1 2004 366 +1461.0 -28.5650 -198.2742 -0.268264
1 2005 365 +1827.0 -28.3388 -219.5665 -21.560536
1 2006 365 +2192.0 -28.4127 -212.5768 -14.570837
1 2007 365 +2557.0 -28.4848 -205.5685 -7.562580
1 2008 366 +2922.0 -28.5551 -198.5422 -0.536216
1 2009 365 +3288.0 -28.3283 -219.8264 -21.820466
1 2010 365 +3653.0 -28.4024 -212.8393 -14.833377
1 2011 365 +4018.0 -28.4747 -205.8336 -7.827690
1 2012 366 +4383.0 -28.5451 -198.8098 -0.803855
1 2013 365 +4749.0 -28.3177 -220.0860 -22.080063
1 2014 365 +5114.0 -28.3920 -213.1015 -15.095591
1 2015 365 +5479.0 -28.4645 -206.0984 -8.092480
1 2016 366 +5844.0 -28.5350 -199.0771 -1.071182
1 2017 365 +6210.0 -28.3072 -220.3453 -22.339328
1 2018 365 +6575.0 -28.3816 -213.3634 -15.357478
1 2019 365 +6940.0 -28.4542 -206.3629 -8.356951
1 2020 366 +7305.0 -28.5250 -199.3441 -1.338196
