Re: [APML] Pentax 67 165mm f/2.8 lens

[KGKIRKLEY@aol.com]

In a message dated 3/28/02 10:52:10 AM, bobm@koyote.com writes:

>I've necer shot this lens wide open and was just curious as how good/bad
>it
>
>was. Anybody have some experience?
>
>Bobby Middleton

Bobby:
The Pentax 165mm f2.8 lens is an excellent lens for widefield 
astrophotography.
Tony Hallas used it to do some of his Hale-Bopp images.
I would suggest stopping it down to f4 or 5.6 for sharper edge stars.
The infinity focus mark is not always the best for stars.
I would suggest placing a piece of tape on the focus barrel with closely 
spaced lines on it and shooting a focus test. This is explained in Robert 
Reeves' book on widefield astrophotography. You bascially shoot a star trail 
image, letting a star field trail for a few minutes at each focus setting. 
When looking at the processed frame, you'll see the star trails will be 
varying widths, the thinnest being the best focus position.

Kent Kirkley

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