How to Make Solar Filters (and Why You Might Not Want To)

This Expert Voices mainstay is from Bob Baer, who leads a open astronomy observations and ubiquitous production overdo events in a production dialect during Southern Illinois University (SIU) Carbondale He has been heading SIU’s eclipse-outreach efforts for 3 years, in expectation of the 2017 sum solar eclipse that will cranky a U.S. from seashore to seashore on Aug. 21. 

With reduction than dual weeks to go until a Aug. 21 sum solar eclipse, we should possibly have a devise in place for where we will perspective this astronomical event, or fast be creation a plan.  

You should also comprehend that there is not a lot of time left to learn new solar observation and imaging techniques. It’s not compulsory to have a telescope or binoculars to observe and conclude a sum solar eclipse, and photographing eclipses is tricky. But if you’re fervent to use your possess apparatus to observe a object on obscure day, my best recommendation during this indicate is to get a few filters for your many vicious solar-viewing apparatus and leave a rest during home. Below, I’ll explain that apparatus we should cruise vicious and how to make your possess solar filters when necessary. [The Best ISO-Certified Gear to See a 2017 Solar Eclipse]

Skywatchers observe a object with solar-viewing eyeglasses and label viewers.
Credit: Ulet Ifansasti/Getty Images

Your No. 1 many vicious square of apparatus is your eyes. Everyone who skeleton to perspective a obscure (total or partial) should have an obscure spectator label or solar observation glasses to strengthen a eyes. These viewers cost about $1 each. For me, a label is some-more accessible than eyeglasses as we customarily wish to reason it in front of my eyes usually quickly to check on a moon’s swell opposite a face of a sun. (Once a moon totally covers a object during totality, it is protected to demeanour during a obscure with a exposed eye.) 

If we can’t find a card, get a span of glasses; we suggest slicing a ear pieces off. we do this since we don’t ever need them. If we are disposed to losing things, punch out a hole in a dilemma of a label spectator or your span of eyeglasses and place it on a lanyard for obscure day. You now have a means to strengthen a best and many vicious obscure spectator we have. [How to Film or Photograph a 2017 Solar Eclipse Like a Pro]

The prejudiced obscure proviso of a Mar 9, 2016, sum solar eclipse, seen from Tanjung Pandan, Indonesia, with clouds manifest in front of a sun.
Credit: Bob Baer/Sarah Kovac/Citizen CATE Experiment

If we will be holding additional apparatus — such as telescopes, binoculars or cameras — to a eclipse, take register of what we wish to use and confirm what we wish a solar filter for. You’ll need a filter for any device we wish to use to observe, sketch or film a prejudiced phases of a eclipse. 

You do NOT wish to take vast scopes to an eclipse-viewing eventuality as a first-time obscure viewer. Think compact, personal and easy to use when selecting a telescope. The images here were taken with a compact, 80mm scope, that provides copiousness of orifice to get decent views of a obscure and constraint decent images.

The solid ring proviso of a Mar 9, 2016, sum solar eclipse, seen from Tanjung Pandan, Indonesia.
Credit: Bob Baer/Sarah Kovac/Citizen CATE Experiment

If we need solar filters for your equipment, a many careful and maybe simplest thing to do is to buy a square or dual of a common solar reserve film. Be certain to get a form of film that is rated for visible use. Two manufacturers of good peculiarity visible solar film are Baader Planetarium and Thousand Oaks Optical. A color-neutral film like a Baader AstroSolar reserve film will yield images of a object with no tone correction. Filters like this always go on a front of a range before any optics (lenses or mirrors). If a telescope we intend to observe with has a finder scope, we suggest stealing it before to solar viewing; this will keep we from incidentally looking by an unfiltered finder scope.  

Sheets of solar reserve film typically come with instructions we should follow. If you’re not certain what you’re doing or if this is a initial filter you’ve made, find assistance from someone with experience. Get additional film, make a filter and exam it out. Once your filter is finished, we might exam it by holding it in front of your eyes and observation a object or an heated light. The picture of a object we see should demeanour identical in liughtness to what we see yet obscure glasses. If we see an picture of a object that is uncomfortably bright, or see a splendid indicate of light anywhere in a filter, it can be an denote that we have a pinhole or other repairs to a film. Do not use a controversial filter. 

It's probable to buy appendage solar filters for some telescopes. The Celestron EclipSmart solar filter can fit on some Celestron PowerSeeker telescopes. Explore Scientific's Sun Catcher non-static large-aperture solar filters are accessible in many sizes.

It is comparatively easy to make your possess filter with some poster-board material, filter sheets, and a small glue and tape. In a pinch, we can even cut out a square of filter element and bond it to a lens with a rubber band. One good thing about a filter film is we can simply transport with all a materials compulsory to make filters on site once we get to your obscure location. That way, we won’t repairs a filters in transit. 

When operative with a film, it is best to wear gloves so that we don’t get fingerprints on a film or differently repairs it. If we do repairs a film, toss it and use a new piece. The film is unequivocally inexpensive compared to a cost of deleterious your apparatus or eyes. With filter in hand, we are prepared to make your possess images and see a object in white light.   

The sun, seen by an in H-alpha filter on a Lunt SUNlab.
Credit: Steven Pizzo

Now, behind to that devise we should be creation about where to see a eclipse. First-time obscure viewers should severely cruise going to an obscure event. At an event, such as a one is holding place during my university, SIU Carbondale, we will be means to accommodate others with identical interests, take prejudiced in a accumulation of peculiarity events and of march see a eclipse. At many obscure events, we will also expected find solar telescopes set adult by gifted observers, so we can get a minute demeanour during a object during a prejudiced phase. 

One of a singular things that will be in place during SIU Carbondale is a Lunt SUNlab, a mobile solar-observation lab that captures high-resolution images of a object in mixed wavelengths. The images will be seen via events on campus as good as streamed by a NASA EDGE Eclipse 2017 MegaCast live from SIU Carbondale. 

The picture above is a SUNlab exam image; to see some-more images, check out Steven Pizzo’s Instagram feed

Once we see a imagery that this lab can produce, you’ll expected know because we should leave a complicated apparatus during home and only suffer a obscure and imagery being constructed for you. 

Bob Baer is a member of a Astronomical Association of Southern Illinois and is a co-investigator for a Citizen CATE (Continental America Telescopic Eclipse) Experiment. He is co-chair of a Southern Illinois Eclipse 2017-2024 steering cabinet and is coordinating scholarship and overdo partnerships for a SIU Carbondale obscure events.

Editor’s note: has teamed adult with Simulation Curriculum to offer this overwhelming Eclipse Safari app to assistance we suffer your obscure experience. The giveaway app is available for Apple and Android, and we can perspective it on a web. If we take an extraordinary print of a Aug. 21 solar eclipse, let us know! Send photos and comments to:


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