My personal opinion is that the poster was wrong. The length of the
star trail on film or sensor is only influenced by focal length. But,
like CoC, the final effect is controlled by total magnification.
Chuck Norcutt
Carlos J. Santisteban wrote:
> Hi, Chuck and all,
>
> Hi Chuck and all,
>
>
> From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
>
>> 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.
>
>
> Yeah, but I'm a bit more tolerant, I use 1000/focal length -- a slight trail
> at every star is OK. See this pic, 12 sec with Canon FD 85/1.2 Aspherical,
> Fujichrome 400 @ 1600:
>
>
> <http://cjss.sytes.net/atachaos/sagitario.jpg>
>
>
>> But I guess that
>
>> probably for the celestial equator so maybe Ursa Major can stretch the
> rule.
>
>
> Sure. And a low-resolution web pic is going to be more tolerant, too.
>
>
>> Confusing to me was a statement that the "rule of 600" was independent
>
>> of format and dependent only on focal length.
>
>
> I have to admit I "never" do Astrophotography other than 35mm format... but
> maybe this rule is, like depth of field, related to a certain CoC, thus
> larger on bigger formats.
> Cheers,
--
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