DIY Solar Filters for Binoculars

Did you know that you can do star-gazing during the day? Our own star, sun, in-fact provides the most spectacular star-gazing experience you can ever do with its full glory, color and true spherical appearance.  You need the right equipment though to do it safely, especially during a solar eclipse, when many people mistakenly think that sun is not as bright during the eclipse. In fact, solar rays can be as damaging during eclipse as staring at at the sun unobstructed.


solar disk

Your options are to get a telescope with a special solar filter or just use regular binoculars fitted with DIY solar filters. The more powerful the binoculars, the better. This article will demonstrate how to build a Do It Yourself solar filter that perfectly fits your binoculars. For this project I will use Bushnell 10×50 binoculars and will provide cut-out templates for its size, but any pair of binoculars should work – just make your own template and print it out. (You can use something like youidraw.com to create vector drawings free without software download).

Materials & tools required:


Bushnell 10×50 binoculars (or any binoculars you already have)
Black Polymer Solar filter sheet
Thin cardboard sheet
Scissors or Utility/Razor knife
Clear, gift wrapping tape
Printer (to print out template)
Filter cut out template (pdf)
PVC coupling or pipe 2.5 inch diameter (or diameter that is larger than your binoculars large input lenses)

Step 1.
Print out the Filter cut out template at 100% size (un-check any options to scale, fit-to-page, etc. in your printer dialog window).

template preview

Step 2.
Cut out the templates and use template A to draw two circles on the polymer sheet with pencil. Use template B to draw doughnut shapes on thin cardboard sheet.
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Step 3.
Carefully cut-out the drawings you have made with sharp scissors (Tip: keep protective cards on polymer sheet while cutting).

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Polymer sheet cut-out
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Cardboard cut-out

Step 4.
Prepare the cylinders. I happened to have a couple of wide media core ends available that were a just a perfect (loose) fit to my binoculars, but you can also use a 2.5in or size that fits your binocular lens PVC pipe or coupling (your local hardware store should have many different ones you can choose from) .

I sawed the core ends to form two pipes with tapered ends.

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Step 5.
Drop he polymer circle sheets into the pipes. Then slide the cardboard “doughnuts” on top for them to hold the polymer filters circles. If your pipes do not narrow on the inside, simply glue or tape the cardboard “doughnuts” that we cut out earlier to one side of the pipe. Then cut out two more cardboard “doughnuts”. Slide the polymer filters and finally slide the cardboard “doughnuts” on top  to hold the polymer filters. Tape the cardboard “doughnuts” from the inside as shown below.


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Step 6.
Add some friction grips. For this I used foam packing peanuts. Cut three thin pieces of packing peanuts for each lens (6 total), to the thickness that can pack the gap between the binocular and the solar filter just tightly enough to hold them securely. Tape the foam pieces in 120 degree interval as shown below.

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Step 7.
Now carefully slide both lenses onto the binoculars and make sure they are snug and won’t fall off. If the lenses are too loose, replace the foams with thicker ones. Be sure that the lenses are securely sitting and won’t fall out during use – you don’t want to look at the sun with unprotected binoculars!!!! It will most certainly blind you instantly.

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Step 8.
You are done. Please use extreme caution when looking at the sun with filters.  The way I do is I put binoculars with solar filters on closely to my eyes first, fully lowered and away from the sun. Then raise the binoculars toward the sun. When I am done observing, I keep the binoculars close to my eyes, lower the binoculars pointing well-away or opposite from the sun and only then take the binoculars off. This way I avoid accidentally looking at the sun without the eye protection.

solar image

DISCLAIMER: You assume all risks for any solar filter build. Extreme caution is required when observing the sun. Do not allow children to use binoculars as they may not be aware of safety issues. Read all instructions and safety information by the polymer sheet manufacturer and fully educate yourself on solar observation safety before proceeding with making your own solar filter or performing a solar observation. The above instructions are for my own record only and I disclaim any responsibility of any harm, permanent blindness or any type of injury any solar observation may cause you.

4 thoughts on “DIY Solar Filters for Binoculars”

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  3. Hello, thanks for this post, really helpful!
    one question however:
    How many solar filters were required for this? One 4×4?
    Thank you.

    1. Hi Alan,

      I had an 8″x8″ sheet that I bought for other purposes and then used leftovers for this project. I would say it depends on your binoculars. Mine has lenses approximately 2.5″ diameter so the 6″x6″ would suffice to make 2 sets of binoculars if need be. Here is the link to that one: http://amzn.to/2f3cLep

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