Re: Photographing the lunar eclipse

Ian Stewart

Thanks Kent, good info … cheers Ian

On May 14, 2022, at 10:53 AM, Kent Blackwell <kent@...> wrote:

Let's hope we have at least ~some~ clearing Sunday night.
I posted this on BBAA Facebook page but in case you're not on Facebook here it is. It's always worked for me. Remember use the "300" rule if you have a 1.5x or 1.6x crop factor camera. For even smaller sensor cameras the formula becomes even more critical.

Photographing the May 15 2022 Lunar Eclipse
If you plan to photograph the total lunar eclipse with a telephoto lens or a telescope remember the “500-rule”. To avoid trailing from the earth’s rotation simply divide the number 500 by the focal length of your lens.
Using the formula you could shoot the moon for 10 seconds with a 50mm lens, but only 5 seconds with a 100mm lens and only 1 second with a 500mm before trailing. My telescope has a focal length of 800mm so it would not be possible to get a descent exposure without a motor driven mount to compensate for the earth’s rotation.
If you have an APS crop frame camera as many of us do, use the “300-rule”. Basically, if you’re going to photograph the moon with a telescope you’ll need a motor drive telescope.
There is no rule for the length of exposure since sometimes the eclipsed moon is bright red and other times it’s so dark as to be nearly invisible. It all depends on how clean the earth’s atmosphere is at the time.
The last eclipse my best exposures with the 100mm f/8 telescope were anywhere from 2 seconds to 15 seconds at ISO 200 or 400, using a crop frame Canon 20Da camera.
Here is a picture I took during the 2019 eclipse viewed from the Chesapeake Planetarium. Using the above equipment, the exposure was 5 seconds at ISO 200.
Weather permitting; we’ll once again be at the planetarium from 9:00 pm.
Kent Blackwell

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