1.22 or 2.44 wavelength * F ratio?

Hi,

In determining the size of the airy disc in diameter, do you use:

1.22 * wavelength * f-ratio

or

2.44 * wavelength * f-ratio?

The latter is twice greater than the former so there is a significant
difference. What is the convensional formula used?

On Aug 22, 9:20*am, Ron Cuaz wrote:
Hi,

In determining the size of the airy disc in diameter, do you use:

1.22 * wavelength * f-ratio

or

2.44 * wavelength * f-ratio?

The latter is twice greater than the former so there is a significant
difference. What is the convensional formula used?

Some source like http://en.wikipedia.org/wiki/Airy_disk give it as:

1.22 * wavelength * f-ratio

other source like http://www.specialoptics.com/pdf/wp_...er_theory..pdf
give it as:

2.44 * wavelength * f-ratio

What is the consensus here? What do you think is the right one?

On Sun, 21 Aug 2011 21:48:06 -0700 (PDT), Ron Cuaz
wrote:

What is the consensus here? What do you think is the right one?

Both. You are not reading the formula descriptions carefully enough.
The 1.22 version is giving the angle from the optical axis to the
first minimum. That is the _radius_ of the Airy disc. The 2.44 version
is explicitly giving the _diameter_ of the Airy disc. The formulas are
saying the same thing.