Avert Your Eyes (and Lenses)

Reflecting on the year: This year is drawing to a close and as part of a retrospective look on the year I am finishing and publishing several blog posts that at one point I started and never completed. Here is a follow up post to on seeing the total solar eclipse in August.

 

I’ve shared my photos of my experience viewing the total solar eclipse, but there is still another story to tell that starts weeks before the eclipse. How to prepare to be able to point a camera with a magnifying lens directly at the sun for a couple of hours without anything catching on fire.

The sun is an extremely powerful light source. Without proper protection it can melt many little parts of the camera. The camera might survive one or two quick photos but I was planning on leaving this on a tripod pointed directly at the sun for the entirety of the event. For that I needed a special solar filter. This is a much more potent filter than what is in the eclipse glasses usually 3 to 4 ND stops higher. This is needed because these filters are going in front of cameras and telescopes that are focusing a large amount of light into a small point, like burning ants with a magnifying glass.

Some solar filters come with a cardboard cutout the slips over the camera lens easily. The ones that I was able to get we’re just squares of aluminized plastic with no easy way to mount them. This is not uncommon for filters or gels; a professional photographer would have the mount needed to affix this, but I didn’t. These mounts are expensive and the eclipse is only a few days away, it would be hard to get. Maybe I can just make one?

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Test printing lens attachment

Some quick measurements and some computer aided design work later and I had a working prototype that could mount the filter to a lens with some rubber bands. Testing reviled that some light was getting in behind the filter and reflecting into the picture leading to some interesting photos, but adjustments we’re needed.

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Solar filter attached to printed lens hood with rubber bands

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Front plate added to keep filter aligned

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Testing the set-up

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Early test exposure through the mounted filter

Version 2 worked much better be I wanted a faster and more reliable way to attach and detach the filter, as the solar filter would need to be removed for the two minutes of totality. Third and final iteration added magnetic latching so the filter can just snap on and off from the base. Still not perfect but good enough, it was time to head to Oregon for the eclipse.

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The final more robust version with magnetic release

As seen in the previous posts the system worked well, and I’m very happy with the pictures I got. Building this system has spurred an interest in astro-photography, and there is so much that can be done with homemade equipment. This is something that I might continue.

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Testing the final setup the day before the eclipse

Who Turned Out the Lights?

As mentioned in my previous post I had the opportunity to go down to Oregon to see the total solar eclipse. It was well worth the trip down and the traffic up as seeing the entirety of the eclipse was very different than the 93% in Seattle or the 99% in Portland. Though stock was scarce I managed to get a solar filter for my camera and setup with a tripod and a telephoto lens to capture this astronomical oddity.

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Just after C1 first photo I was able to capture as I was formatting my camera card as first contact was made to make room for all the eclipse photos.

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About half an hour latter the moon is nearing the half way point. Around this time it starts getting noticeably cooler.

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Through the camera or eclipse glasses the sun is now a sliver behind the moon. Without the glasses the only noticeable change is that sun light seems dimmer. This is about as much of the eclipse would have been seen in Seattle.

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The sun gets smaller and smaller. This is about the extent of the eclipse that would have been seen from Portland.

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An interesting phenomenon know as Bailey’s Beads. The last rays of sunlight are sneaking through the mountains and valleys of the moon, making the appearance of a string of beads. 

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Totality. Now the glasses and solar filters can come off as the sun is completely eclipsed by the moon for 1 minute and 44 seconds. In the sky there is a black circle surrounded by white rays which is the sun corona, only visible to the human eye during a total eclipse. Stars are visible and the entire horizon looks like a sunrise. 

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As C3 passes the total eclipse ends I sneak a picture of the ‘Diamond Ring’ before putting the solar filter back on the camera. 

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The sun is back to being a sliver, and the entire process reverses its self. Around this point we did notice some light Shadow bands snaking across the ground.