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Tog
2010-Jan-25, 06:36 PM
I may have found an error in the book Starlist 2000. It's a catalog of stars that includes the basic formulas used in astronomy. Since I had sucha hard time at Algebra, I try to run through the examples of how to used the formula to make sure I'm doing it right. In this case it seems pretty straight forward, but I get a different answer.

The sample is comparing the magnitudes of Deneb and Arcturus, 1.25 and -0.04 respectively. The method is given as:

2.512(m2-m1)
which comes out to be
2.512(1.25+0.04) or 2.5121.29

WhenI put that in, it comers out 3.28. The book gets 3.05. which would be 2.512(1.25-0.04).

Did they mess up the sign in the formula, or did they drop it from the calculation in the example?

Thanks.

hhEb09'1
2010-Jan-25, 06:55 PM
Did they mess up the sign in the formula, or did they drop it from the calculation in the example?
I think the formula is right, but another possibility is that the magnitude of Arcturus should be a positive 0.04 :)

The resource I use lists it as 0.16

grant hutchison
2010-Jan-25, 08:50 PM
The formula is definitely correct.
Each difference of one magnitude represents a multiplication factor of ~2.512. So we need to find the difference in magnitudes and raise 2.512 to that power, just as the formula does.
My first couple of paper references off the shelf give the visual magnitude of Arcturus as -0.04, so at present I'm leaning towards someone messing up the double negative when doing the calculation for the book.

Grant Hutchison

Tog
2010-Jan-25, 09:26 PM
So... what you gus are saying... if I'm reading it right... is

This math error wasn't mine! YES!

Ahem.

Sorry.

And thanks :)