Relative air mass formula in Excel

[**KJ17**]

I am preparing a spreadsheet for cooling load calculations, but I am running into a problem with one formula.

I try to add the following formula into excel.

m=[sin b + 0.50572*(6.07995 + b)^-1.6364

b = 57

The actual formula and result are displayed below

Beam normal irradiance Eb
Eb = Eo exp(–τbmab)
m = relative air mass
= 1/[sinβ +0.50572(6.07995 + β)–1.6364], β expressed in degrees
= 1.18905

I am completely lost.

Please help!

Regards,
KJ

[Glenn Kennedy]

Can you point me to a URL where I can see the equation clearly (I get 2.2897 in my first attempt...)

[**KJ17**]

Good afternoon Glenn,

Thanks for your prompt response.

Below the URL with a clear view on the equation.

http://en.wikipedia.org/wiki/Air_mass_%28astronomy%29

KJ

[Glenn Kennedy]

I still get the same answer... 2.2897... I've taken the equation from Note 3. What (if any) is the significance of the ° after the 6.07995, other than the unit of degrees? How confident are you that the answer SHOULD be 1.18905?

[**KJ17**]

Thanks for your answer.

I have made a change to your excel formula, by converting the actual numbers to radians instead for degrees.

I have attached the file with the changes.

The results look perfect!

Again thanks for your help and assistance.

Have a great day!

Regards,
KJ

[Glenn Kennedy]

Woo Hoo!! If that's all, can you mark the thread as solved and (preferably) click the Add Reputation button at the foot of this post.

[indrabapoek]

Sorry, if i brought up this old thread.

I want to calculate the air mass using the formula mentioned above. But, when i input a negative number (say -35 degree), it got the !NUM# error.

Any suggestion?

Thanks be4!

[JohnTopley]

Taking the previous posted examples, if A1=x degrees, converting to RADIANS give a result......??

=1/(SIN(RADIANS(A1))+0.50572*POWER((RADIANS(A1)+6.07995),-1.6364))

[indrabapoek]

Wow, it really worked!

Thanks so much!