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500 rule for astrophotography and m43?

Started Sep 23, 2015 | Discussions thread
Eric Nepean
Eric Nepean Veteran Member • Posts: 6,209
Re: 500 rule for astrophotography and m43?
2

bobbip wrote:

Hello,

Off to the Red Centre and hoping to work on my astrophotography. Previous attempts had streaked stars at 50s exposure for 12mm.

I've been told the divide 500 by your focal length rule is for full-frame equivalent to keep stars from trailing.

Can the experts amongst us tell me what the "500 rule" is for m43? I hope to take many photos and stack them (as well as experiment with live composite for star trails). e.g. at 12 mm what's the maximum exposure before trailing occurs without a rotating/astro tripod?

Thanks,

Bobbi

I think the formula 209/FocalLength is correct for M43, but 250/FocalLength is close enough, especially if you are using JPEGs.

I made a spreadsheet calculation where I set the constraint that the star image should move the diameter of the CoC (circle of Confusion). For M43 I used a .015mm CoC, which works out to be just under 4 pixels for a 16MP sensor. I used the the maximum angular velocity, which occurs at the celestial equator, or approximately the suns path.

I get the result that the shutter speed should be faster than 209/FocalLength for an M43 camera.

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Eric
When the light is gone, the picture is gone ....

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