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Pedro Cabral wrote:
> -Where in the tutorial is the "Te2" variable, inluded in EL's, formula 
calculated? "Te" is calculated elsewhere in the tutorial but not "Te2";

I assume the equations are in this message:

http://fer3.com/arc/m2.aspx/how-are-tables-for-declination-generated-equation-etc-WSMurdoch-feb-2005-w22034

I don't have any of Murdoch's references at hand, but I suspect the 
first terms of the EL formula

1018585.1+(6191.2*Te)+(1.1*Te2)

are a 2nd degree polynomial approximation of the Sun's motion. If I'm 
correct, Te2 means Te^2, i.e., Te * Te.

That typo can happen when you copy and paste from an HTML document 
(where the 2 is a superscript) to a plain text message.

The polynomial can be rewritten as

1018585.1 + (6191.2 + 1.1 * Te) * Te

to save the machine some work. In general, any polynomial such as

a + b*x + c*x^2 + d*x^3

can be factored to

a + (b + (c + d * x) * x) * x

The latter is faster for a computer. It can save the programmer some 
work too, if the language lacks an exponentiation operator (e.g., the C 
language). Some programmers write the factored polynomial as:

a + (
b + (
c +
d * x) * x) * x

In my example there's no advantage because the coefficients are 
variables. But when they're numeric constants, that format makes it easy 
to check your source code against the book formula.

Back to the Murdoch formulas – I think the Aries formula also contains a 
2nd degree polynomial:

ARIES = 360*(0.7790573+(36625.0021390*Tu)+(0.0000011*Tu2)
-(0.0000122*sin(N))-(0.0000009*sin(L)))


> -The little square before the 3600 also in EL's formula is supposed to be a division symbol right?

Yes, I think so.

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