ATM Aperture, focal length and airy's disk

["Ashish, Balaya (IE10)" <ABalaya@meghadoot.hiso.honeywell.com>]

Clive Milne writes :
>Ok guys, educate me...
>
>There are two issues here, Aperture and Focal Length.

.....Actually, in the original post the focal length of the two scopes was
the same.

>Larger Aperture collects more light and maybe other things.

..... Yes....people waiting to look through the eyepiece.

>The shorter focal length also changes the size of the Airy (sp) disks.

..... No, the airy disk is purely a function of focal ratio....
...... Resolution is a function of aperture.
...... Focal length merely determines magnification....(as a function of
primary & eyepiece focal lengths)

>The shorter the focal length the smaller the disk.

..... For a given aperture, yes.
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I thought the Airy disk was a function of aperture - the larger the
aperture, the smaller the Airy disk. This correlates with "The larger the
aperture, the better the resolution" because the resolution would depend
upon the Airy disk.
clear skies,
Balaya