# MaxIm DL5 FITS header PTAREA

Forums Spectroscopy MaxIm DL5 FITS header PTAREA

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• #573670
Mr Jack Martin
Participant

I have a C14, does anyone know how to calculate the aperture area in mm^2 ?

Regards,

Jack

Huggins Spectroscopic Observatory UK

#577815
Andy Wilson
Keymaster

Hi Jack,

First, just to note that PTAREA is not one of the FITS header requirements for BeSS, in case this is why you are asking.

To calculate the area you use the formula for the area of a circle.

Area = pi x radius squared

The Celestron website gives the diameter of your C14 as 355.6mm, so the radius is 177.8mm. Thus the area would be:

3.14159 x 177.82 = 99315mm2

This does not take into account is the central obstruction in your C14. Again the Celestron website gives this as 114mm, so a radius of 57mm. Thus the area of the central obstruction would be:

3.14159 x 572 = 10207mm2

So the actual light collecting area of your C14 will be:

99315 – 10207 = 89108mm2

Cheers,

Andy

#577817
Mr Jack Martin
Participant

Andy,

Thank you for you step by step reply.

This information does not appear to be available from Celestron when looking at the C14 specs or anywhere else.

Regards,

Jack

Huggins Spectroscopic Observatory UK

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