500 Rule -long exposures - Amateur Astro Photography
Stills by Larry Waite
Larry Waite
Stills by Larry Waite
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500 Rule -long exposures
Tips
The classic "500 Rule" referrs to the cameras setting to get a good exposure of the stars.
This rule will assist in avoiding star trailing.
It is quite simple:
Divide your focal length of your lens into 500.
Ie: 10mm lens would be 500 divided by 10 which equals 50 seconds.
That is, I can have my shutter speed at a maximum of 50 seconds to avoid star blur (trailing).
An 18mm lens would be 500 divided by 18 = 27Seconds.
But wait!
That is if you have a full frame camera. I dont, I have Nikon crop sensors.... so..first I have to first mulitply my lens's focal length by 1.5.
before applying the 500 rule. My 10mm lens, multiplied by 1.5 = 15.
The 500 rule for me now is 500 divided by 15= 33 seconds ( I find 30 is perfect)
Some people use a 400 rule instead of 500. Try both and see how you go. (400 almost guarantees no star trail affect)
Here is a useful chart from Astrobackyard to work out your exposure time.
