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A comment on A method for improving Milky Way exposures in light pollution.

Re:A method for improving Milky Way exposures in light pollu... by johndoe90 on Tuesday September 12, 2017 @04:39AM (#15225747)
I wonder where are the star trails. Wouldn't 30s exposure make earth movement noticeable?
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Re:A method for improving Milky Way exposures in light pollu... by hug on Tuesday September 12, 2017 @05:50AM (#15226001)
The answer is the 500 rule. To avoid star trails, exposures should be less than 500/focal-length-in-135-equivalent.

In other words, if he shot this on his 'favourite' Rokinon 24mm, an exposure time of 20 seconds is reasonable to avoid all star trails.

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Re:A method for improving Milky Way exposures in light pollu... by johndoe90 on Tuesday September 12, 2017 @06:09AM (#15226072)
Didn't know that one. Thanks a lot!
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