January 11, 2024

Binocular Solar Filters

Katie and Gene Hamilton

Bring Binocular News

Take a step further observing the sun by adding solar
filters to your binoculars

Observing the sun is an “afternoon delight” an ideal pastime for those of us who have difficulty staying awake late into the evening. Since the sun is earth’s nearest star, it’s just waiting to be explored. Stroll outside on any sunny day and look for the sun using binoculars with solar filters. That’s a key phrase “binoculars with solar filters” to protect your eyes from damaging sunrays. Looking at unfiltered sunlight is dangerous and can burn your eyes’ retinas. Without taking precautions that could lead to serious eye injury or permanent blindness. Don’t think sunglasses are enough protection, they are not.  Use an approved solar filter set designed for binoculars.

Don’t get a UV filter which is designed to prevent UV-induced ‘haze’, a  photography filter.  An ISO certified Solar filter is designed to block all but 1/100,000th of the Sun’s light. Most glass solar filters produce a yellow or orange tinted image while polymer solar filters produce a white-blue image. We were going to get a set of solar filters for out binoculars to observe an eclipse so we asked for some advice from High Point Scientific, (highpointscientific.com) to learn what size of solar filters we needed for our 20×80 Zhumell astronomy binoculars.

Nicole Smith, a telescope and astronomy expert asked me to measure the outer diameter of the binoculars, along with an image attached for reference, which I did. After receiving my response of 4-inches, she suggested “Baader ASBF 100 AstroSolar filters.

This filter has adjustable rubber coated fingers that fit several sizes of binoculars or telescopes. Once adjusted the fingers grip the side of the binoculars’ barrels.  There are safety straps that fasten to the side of the barrels to hold the filter snugly in place. These straps attach to Velcro tabs that stick to the sides of the binoculars. This allows the safety strap to be easily removed with the filter.

The more magnification binoculars have creates a narrower field of view.  We used a red dot finder on these binoculars to make it easier to spot what we were looking for, especially at night with a sky full of stars. But we found the RDF did not help finding the sun since we had to look directly at the sun to place the red dot on it.   

Another type of finder especially designed for aligning the binocs with the sun is a Sol-Searcher by Tele Vue. This device has a small hole at the front that lets a beam of sunlight shine on an opaque opening at the rear.  When the Sol-Searcher is pointing directly at the sun, sunlight coming through the front hole shines directly on the rear opening. Once the finder is aligned, pointing the binoculars at the sun is easy. Just point the binoculars in the general direction of the sun and then do some final movement of the binocs until the sunlight shines on the rear opening on the Sol-Searcher. Remember don’t look directly at the sun.

The bracket that the RDF is sitting on is a Baader Planetarium Binocular ABS Adapter. Removing the Red Dot provides a stable platform to mount the Sol-Searcher. A piece of duct tape holds it in place and alignment is quick and easy.  

Resources

Baader ASBF 100 AstroSolar filters

https://www.highpointscientific.com/baader-astrosolar-100mm-binoculars-solar-filter-asbf100

Baader Planetarium Binocular ABS Adapter

https://www.adorama.com/aassiiibin.html?gclid=EAIaIQobChMIxInvsPq5gQMVyPXICh1DJgCoEAQYBCABEgLhdPD_BwE&gclsrc=aw.ds&utm_source=inc-google-shop-p

Sol-Searcher by Tele Vue

https://www.highpointscientific.com/tele-vue-sol-searcher-solar-finder-ssf-1006

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Gene and Katie Hamilton are long-time writers about using binoculars for boating, bird watching, stargazing and traveling. They are members of the Outdoor Writers Association of America.


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