Re: (meteorobs) Shooting the skies

Terry Richardson wrote:

> Actually the effects of diffraction are quite dependant on the focal length
> used and are not always evident in real tests.

I wasn't aware of the focal length dependency.

I certainly agree with you that the only way to determine the correct
aperture for maximum resolutiion is by test!  There are just too many
variables in workmanship and design details to truly generalize.

I would like to take this opportunity to assure people that you can get
good images and sensitivity with inexpensive equipment.  The camera and
lens I use cost $99 Cdn ($66 US) in 1989.  The lens is a 58 mm f/2.

BTW a big convenience of 58 mm is that is approximates the number of
degrees in a radian.  At this focal length 1 mm on the negative equals 1
degree of arc.


John Ohrt *** Toronto, ON, Canada *** mailto:johrt@ultidot net