At 10:19 AM 2/6/98 -0500, Rob Roy wrote:
>>Last week a friend showed me his newly acquired 180mm/f2.8 Zuiko which he
>>had purchased for just over $300 CDN (~$200US). From the outside the lens
>>was like new. I was envious that I hadn't been in the camera store first.
>>
>>Last night he showed me some astrophotos he had taken before he took the
>>lens back to the store. I have never seen anything like them. The stars
>>were football-shaped (astigmatism) and the brighter ones had blue halos
>>around them (chromatic aberration). Any ideas as to what is going on? I
>>have never even heard of such a bad lens!?
Tomoko Yamamoto (another contributor to this list) suggested that your
exposure time may have been too long. Anything longer than about 20-30
seconds, at any reasonable magnification, will not show the stars as point
sources but as "doughnuts," and even longer exposure times will show a
distinct arc line. Unless your buddy was using a tracking rig, long
exposures will produce such problems. I'm at a loss about the chromatic
aberration, though, if it *was* that.
Garth Wood
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