Photographing the Solar Eclipse
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Wednesday, August 23, 2017
By Dave Margaretos

August 21, 2017 was a special treat for millions of American across fourteen states who were able to view a total eclipse of the sun. At my home on Cape Cod in Massachusetts we were only provided with a partial eclipse of about 65% but I was determined to make the most of it and photograph the event. Some of my motivation came from wanting to participate in this rare event but much of it was the photographic challenge. I'm glad I made the effort as it was a thrilling experience and I'm please with my photographic result.

I started about a month before the event with some internet research of the details of the eclipse itself: date, time, duration and how to go about making a successful photograph. Critical to the process is a solar filter which allows the photographer (and the camera) to safely view the sun. These filters are nearly opaque and block about 99.999% of the sun's light which in photographic terms is the equivalent of about 18 photographic stops of exposure reduction. Without this filter you would permanently damage both your retinas and the camera's digital sensor.

I soon discovered what I should have guessed. Most serious photographers had long ago ordered their solar filters and, for example, every one of the thirty or more solar filters listed by B&H Photo were sold out and back ordered. At that point I decided to make my own filter which turned out to be fairly easy and very economical. For $16.00 I was able to purchase a 6" x 6" sheet of  polymer solar filter material from Thousand Oaks Optical that is manufactured for astronomy uses. The lens I had chosen to use had a filter thread diameter of 77mm so I purchased a 77mm to 86mm step-up ring for $8.95 from B&H. To make the filter I traced the 86mm side of the step-up ring onto the polymer film with a Sharpie and cut out the circular piece. Finally, I carefully glued the circular disc into the 86mm side with the silver side facing out (towards the sun). Presto, a solar filter!

I selected a  Nikon 80-400mm lens to use in conjunction with a Tamron A300fNS 2x tele-converter which increased my effective focal length to 800mm. Tele-converters introduce a number of optical flaws and for most work I would not use one; however, the image of the sun has little detail so I opted to go for the greater magnification and not worry about image quality. The lens and tel-converter combination provided an image of the sun that filled about half of my viewfinder which was what I wanted. Although the tele-converter was auto-focus I chose to manually focus to minimize the need to find an edge for the auto-focus mechanism to work on.  

Using a Nikon D700 I set  the exposure mode to manual and determined my exposure a through a series of trial and error shots. I ended with an exposure of f/16 at 1/400 second using an ISO of 1600. I chose this relatively high ISO speed because I wanted my aperture to be in the middle range of my lens and a faster shutter speed to counter any camera or tripod shake when I released the shutter. This exposure gave me an image of the sun that had a nice golden-yellow color (with a histogram that was not clipped) and a black background which made for a nice sharp image. 

I mounted my camera and lens on a Giottos tripod with a Manfrotto ball head and 360⁰ panning platform. This made it easier to track the sun and moon as they moved across the sky during the 2-1/2 hour duration from the start to the end of the eclipse. This tracking turned out to be the hardest part of the process. Beginning with the start of the eclipse I made an exposure every 5 minutes and owing to the high magnification I needed to adjust the camera trajectory for every shot. It was important to never let the image of the sun "leave" the viewfinder as it can be hard to relocate because the solar filter is so dense that you can see nothing other than the sun. As this happened a couple of times I was glad that I was using a variable focal length lens which allowed me to zoom out to a wider field of vision so that I could locate the sun. 

The rest was fairly easy. In-between making an exposure every 5 minutes I was able to catch up on some reading and observe the changes in my yard as the eclipse came and went. Although it did not really get dark the light quality changed to "dingy", the birds stopped chirping, the temperature dropped and a little breeze picked-up. As the eclipse ended all of these reversed and soon enough life was back to the way it had been before the eclipse.

To make my final photo I selected five images. I started with the mid-point which showed the maximum eclipse and then added two that showed the very first and very last views of the moon. Finally, I added two from the midpoints between the start and mid-point and the mid-point and the end. I cropped  the five images to the same size and resolution and merged them onto one canvas in Photoshop. Finally, I annotated my photograph with the date, time and latitude/longitude and the result is above.

On April 8, 2024 New England will be treated to a total solar eclipse. Beginning in Southern Texas, the path of totality will pass through Dallas, heading northeast through Little Rock, Arkansas; Indianapolis, Indiana; Cleveland, Ohio; Buffalo, New York and Burlington, Vermont. Although Boston will only get a near total solar eclipse at 92% it will be a spectacular photographic event. There are 2,422 days to prepare so we should all be ready!

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1 Comment
Bob Gould - Dave,
Great job and great story. Thanks for sharing the images and the history behind them. Very clever,

Bob


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