Despite the amount of time I spent with telescope (and sometimes scope
and camera) in the late 60s and early 70s I never until today learned
the "rule of 600" which states that, in order to keep stars from forming
a trail, the exposure in seconds can't be longer than 600/focal length.
So, with my new bit of knowledge I can guess that the exposure below
was probably not longer than about 50 seconds. But I guess that
probably for the celestial equator so maybe Ursa Major can stretch the rule.
Confusing to me was a statement that the "rule of 600" was independent
of format and dependent only on focal length. That didn't make any
sense to me since small formats typically get enlarged more than large
formats and any apparent motion would be magnified accordingly. Was
that bum information? If not can someone explain?
Chuck Norcutt
Carlos J. Santisteban wrote:
> Hi Ken, Dawid, Chuck, Jez and all,
>
> From: Ken Norton <ken@xxxxxxxxxxx>
>> A similar shot, taken last year at the Badlands National Park with the E-1
>> is here:
>>
>>
> http://zone-10.com/cmsm/index.php?option=com_content&task=view&id=191&Itemid=1
>
> Beautiful picture! Does Ursa Major qualify as the bear you were looking for?
> ;^) BTW, your (geographic) latitude seems much higher than mine...
--
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