Photographing the total solar eclipse August 2017

[BKruse]

This summer, I am planning to share my photographs of the total solar eclipse with a cool project.  The Eclipse Megamovie wants photographs of the upcoming August 21st total solar eclipse to build a movie of images from coast to coast. They need skilled photographers to help create the movie as well as support solar science.  Their goal is to recruit over 1,000 photographers and astronomers who will be on the path of totality on August 21, 2017. Their list of basic equipment necessary for participating in the Eclipse Megamovie Project includes a DSLR, a lens with a focal length of at least 300mm, and a tripod.  Lots of information and a link to apply to join the photo team is on their website:  https://eclipsemega.movie

[kvbarkley]

300 mm is too tiny, I would say at least 500.

[ebiggs1]

The Sun is about the same size as the Moon viewed from Earth.  I also think 300mm is too short.  Check it out by looking at the Moon through a 300mm and than a 600mm.  But it does depend on what you want.

[RobertTheFat]

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@ebiggs1 wrote:

The Sun is about the same size as the Moon viewed from Earth.  I also think 300mm is too short.  Check it out by looking at the Moon through a 300mm and than a 600mm.  But it does depend on what you want.

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Anyone who hasn't attended a total eclipse may not realize how DARK it gets at totality. It's not like photographing the moon on an average night; there's nothing there to see except the sun. So you might as well fill the frame with it if you can.

[kvbarkley]

Or just do the math.

The moon/sun has an angular diameter of about 0.5 degree.

For APS (1.6X) the field of view and the percentage that the moon is of the FOV for various focal lengths is given:

FL    FOV   %moon

300      5.1     10%

500      3.1     16%

600      2.6     19%

1000    1.5     33%

For full frame it is worse, of course

FL    FOV   %moon

300      8.3     6%

500      5.0     10%

600      4.1     12%

1000    2.5     20%

[TCampbell]

I'm also participating in the Eclipse Megamovie.  I'll have several camera under control of Solar Eclipse Maestro software (well 2 cameras..... 3 if we can get Canon to update the EOS SDK so that it supports the 5D IV (hint hint, Canon)).

A Canon APS-C sensor camera would ideally have a lens in the 400-800mm focal length range with about 525mm being nominal.  The Sun should hopefully be at least 1/4 of the height of the sensor in the narrow direction, but not larger than 1/2 the height of the sensor.  1/3rd heigh is nominal.

While normally we think "fill the frame", once totality occurs, the solar corona becomes visible and this will stretch out many times larger than the disk of the sun.  This is why you'll want a lot of extra space around the Sun.

Also the solar corona needs a lot of dynamic range to capture the extent.  The bits of the corona nearest the sun are bright and it gets much dimmer as it gets farther from the sun.  It takes about 12 stops worth of exposure to capture everything.  

This creates a problem for the photographer trying to use manual techniques to capture it all.  Totality only lasts just a bit over 2 mins (maybe 2 mins 40 secs in the longest areas.). That's not much time and time spent with your head in the camera means you are missing the event yourself.

I'll be using a computer to control all the exposures.  Solar Eclipse Maestro (Mac only) and Eclipse Orchestrator (Windows only) are very similar.  Both use the eclipse prediction data (for this eclipse that's the data provided by NASA's (now retired) Fred Espenak - a.k.a. "Mr. Eclipse") with a GPS to determine when the fist, second, third, and fourth contact events (C1 through C4)  will occur for the position where you are located.   Based on that data, it uses relative time offsets to determine when the eclipse phenomena will occur such as the diamond ring effect, the baily's beads effect, and others.  The software will generate a capture script to control your cameras (but you can tweak it) so that it captures the entire event with very little help from the photographer (it does need to yell at the photographer to remove the solar filters as totality is about to happen... and again after totality ends when the photographer should place the filters back on the lens.)