Solar eclipses occur when the moon blocks any part of the sun. Total solar eclipses, however, are only possible on Earth because of a cosmic quirk of geometry: The sun’s diameter is 400 times wider than the moon’s, but it is also 400 times farther away. The result is that the sun and the moon appear to be the same size from our perspective. When they line up just right, the moon can obscure the sun’s entire surface, creating a total solar eclipse. 

 

The solar eclipse will last a few hours from start to finish, but totality of the eclipse only lasts about 2 minutes.   Yes, it is very brief, but truly unforgettable.   Everyone in the U.S. will see some portion of the eclipse (partial eclipse), but only the poeple under the narrow 60-mile wide path that crosses the country will get to witness totality.

 

A total solar eclipse will turn day into night, while a partial eclipse may go unnoticed as it won't look much different than a cloud passing in front of the sun.    With a total eclipse, the sun's corona will appear during totality, and watching it will take your breath away.

 

Capturing the sun as it is eclipsed by the moon is challenging and requires practice and special filters to prevent damage to your cameras.     If you want to ensure that the eclipse fills up the frame, you'll want to consider purchasing or renting a strong telephoto lens as well (400-1000mm equivalent).

 

With all the excitement, noise and cheering, you have less than 2 minutes to take a perfect photograph.  The key to success is planning, and this guide will hopefully get you started.

 

 

 

 

 

 

 

 

 

 

 

 

Solar Filters for your eyes, camera lenses, and binoculars / telescopes

The ONLY safe way to view a solar eclipse is using solar filters.   The filters are specially coated with metal to reduce the intensity of the sun.  The filters quickly attach to the front of your lens, binoculars, or eyes for safe viewing. 

10-Stop ND Filters only block 1/10,00th of the sun's brightness. While this may be acceptable at sunrise or sunset, it's not enough when the sun is higher in the sky.   Solar filters block 1/100,000th of the sun's brightness and are the only safe way of viewing and capturing a solar eclipse.

Solar filters for cameras are usually described as "Full-Aperture" or "Off-Axis" filters. Full-aperture solar filters are preferred because the filter completely covers the front of the lens so that the entire lens is used. No refocusing of the camera lens will be needed when you remove the filter at the beginning of totality or when it is replaced back on the telescope/camera lens at the end of the total phase.

 

Solar Filters:
 

• Black polymer screw-in solar filters

• Silver Mylar solar filters / sheets (less durable than polymer)

• Solarlite Slip on filters

• Glass threaded solar filters

• Rainbow Symphony Slip Over Black Polymer Solar Filter

• Celestron EclipSmart Solar Filter & Glasses Kit
   

Filter cost will depend on the size and quality of the filter. For the average telephoto lens expect to pay from $60 to $100 for the glass type filters, and $20-$60 for film style filters.  For very large lenses (4" diameter, etc.) that cost could reach up to $200 and more for glass filters.

 

As with all things, quality varies quite a bit. Many consider the Baader Astrosolar Film (PHOTO) and hand-made filters to be the best quality.  These filters pass enough light to keep the exposures fast at low ISOs and are considered optically superior to any other Mylar or Polymer material.

 

A solar filter must be used on the lens (and on your eyes) throughout all phases of the eclipse EXCEPT totality.  

 

Practice Ahead of Time:​
To determine exposure it is best to run a test on the un-eclipsed sun on a clear day prior to the actual eclipse (using a solar filter).  Photograph the mid-day sun at a fixed aperture using every shutter speed from 1/4000 to 1/30 second.  Looking at the exposures, select the best shutter speed & aperture combination and use them to photograph the partial eclipse.

 

If you plan to shoot a timelapse, practice ahead of time.  Using a solar filter, solar glasses to protect your eyes, and the lens you plan to shoot with - head outdoors and set up your shot as if you were capturing the start of the eclipse.  Time how long it takes for the sun to move across the field of view.  Try it again, but at a wider focal length.  Try to find that sweet spot the balances the amount of time it stays in the field of view and how large the sun will be in your frame.    

 

If you have a tracking telescope mount make sure you can set it up and get it working each and every time before using it during the actual eclipse.   If you have a motion control pan & tilt head try to set it up so that the head will track the sun as it moves during the eclipse.  

 

Tracking the sun with a video / timelapse MOCO head

The eclipse on August 21st in the Jackson area will last approx. 164 minutes. Since the earth rotates at 15-degrees per hour you'll want to set the motion control head to pan 41 degrees from start to finish and tilt 20 degrees during that same time frame.

The sun's brightness doesn't change throughout the partial phases of the eclipse, no exposure compensation will be needed.   During totality you need to remove the solar filter, and then put it back on once the sun starts to move out of totality.

 

TEST COMPARISON RESULT

Now that the Orion 07733 Glass Solar Filter arrived I finally had the chance to test all four filters.  The Astromania filter (right, white), which uses the Baader AstroSolar safety film, is the only one of the four filters tested that shows the sun in it's natural color, which is white.  The other two filters use Black polymer film which make the sun look "natural orange",  but sunlight is actually white.  

 

While all of the filters are very close when it comes to detail, I found the Thousand Oaks and  the Astromania filters to be the sharpest.  I used the sun spot to compare sharpness between the four filters, and despite thin clouds that had moved in before testing the Astromania filter for the second time, I still feel that it had better detail than the Rainbow Symphony and Orion filters. 

 

The test was completed using a Canon 5D Mark IV and the Sigma 100-600mm lens set to 600mm.  Focus was acheived and never changed between tests of the four filters.  Exposures did change, since each filter needed a little more or a little less light.  A 10-second self timer was used to reduce camera shake at the time the exposure was taken.

 

Click on the image below to open up the full resolution version of this test. You can then magnify the image full screen to see the sun spots captured.