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How To Build a DIY Solar Filter

Building a solar filter for photography or viewing eclipses

Written By on in Projects

873 words, estimated reading time 4 minutes.

This is a simple construction method for a DIY solar filter to be fitted over the front of a camera lens. The filter, in this case, is a section of Baader film and is designed to fit the end of a telephoto lens. Auto focus still functions correctly on my Canon EOS 350d.

I cannot vouch for the safety or reliability of this construction of this Solar Filter, I am merely documenting the construction of a solar filter of my own design. This is the filter that I use on my camera and have experienced no ill effects from its use. Due to the immense danger of looking at the Sun, I cannot advise you that you try or use my method and design, I merely present this to you to show you how I observe the Sun. I will not be held accountable or liable for any injury as a result of following these methods.

  • Never, ever look at the Sun directly through any optical instrument - instant blindness could be the result. Even looking at the Sun with the eye can be harmful.
  • DO NOT look at the Sun with magnifying glasses, cameras, binoculars or telescopes, any optical instrument in fact, without the use of a properly designed, approved and tested filter or specialised instrument.
  • DO NOT use photographic film, smoked or tinted glass, plastic or metal film.
  • Use only materials and instruments designed for the specific purpose for viewing the Sun.
  • If in doubt, seek expert advice first!

That said, this is the design that I use when observing the sun and I can still see. If you have a digital camera that uses an LCD display, there should be no danger of injury as long as you mask out the sun with a screen, or similar. The Sun's light will not follow an optical path to your eye, but rather it will be visible on the LCD, which will only be as bright as the brightest pixel. This is only true for non-SLR cameras, or cameras without an optical viewfinder. If your camera has an optical viewfinder as well as an LCD display it would be a good idea to block off both ends of the viewfinder. You don't want to accidentally look at the sun. Before attempting this you should make sure that you never look directly at the sun at all. I recommend cutting a hole in a large piece of cardboard to poke the lens through. This will prevent you from accidentally looking at the sun and also the LCD will be clearer to see.

If you have a digital or film SLR camera DO NOT LOOK AT THE SUN THROUGH THE VIEWFINDER WITHOUT A PROPER FILTER.

Once more: DO NOT LOOK DIRECTLY AT THE SUN. Instant blindness will be the result.

These are guidelines only and should not be taken as gospel.

Solar Filter Construction
Solar Filter Construction

The construction starts with a piece of corrugated cardboard. You could use any thick cardboard though. It must be strong and non translucent.

Solar Filter Construction
Solar Filter Construction

Start off by drawing around the outside of the lens so we know what size the hole should be.

Solar Filter Construction
Solar Filter Construction

Next mark out lines in a cross shape that will form the face and the walls.

Solar Filter Construction
Solar Filter Construction

Cut out the arms, making each one slightly tapered towards the outside.

Solar Filter Construction
Solar Filter Construction

Next, Using a template the same size as the inner face, cut out a section of Baader film.

Solar Filter Construction
Solar Filter Construction

Using some glue (I used some multi-purpose adhesive) attach the film over the lens opening. Test a small amount of the glue on a spare piece of the solar film, as some will dissolve the protective coating, or the film itself. Others can make the film go cloudy.

Solar Filter Construction
Solar Filter Construction

That template we used earlier needs to have a hole cut into it the same size as the hole in the main face. It also needs to be cut to a smaller size than the face.

Solar Filter Construction
Solar Filter Construction

When suitably cut down, it should be stuck on top of the film, so that the film is sandwiched between the cardboard. Attach some foam strips to the outside edges of the sides. Wait for the glue to completely dry.

Solar Filter Construction
Solar Filter Construction

Fold the sides in on themselves and firmly attach with duck tape or gaffer tape. You should use several layers to ensure that no light can enter and that it is secure.

Solar Filter Construction
Solar Filter Construction

Finished. Here is a view inside the filter.

Remember, I cannot vouch for the safety or reliability of this construction, I am merely documenting the construction of a solar filter of my own design. If you do use it, you do so at your own risk. Please take notice of the warning at the top of the page. I will not be held accountable or liable for any injury as a result of following out this procedure.

  • Never, ever look at the Sun directly through any optical instrument - instant blindness could be the result. Even looking at the Sun with the eye can be harmful.
  • DO NOT look at the Sun with magnifying glasses, cameras, binoculars or telescopes, any optical instrument in fact, without the use of a properly designed, approved and tested filter or specialised instrument.
  • DO NOT use photographic film, smoked or tinted glass, plastic or metal film.
  • Use only materials and instruments designed for the specific purpose for viewing the Sun.
  • If in doubt, seek expert advice first!

Last updated on: Tuesday 20th June 2017

 

Comments
Linda

Linda

where can I purchase Baader film?

Reply to Linda
Tim Trott

Tim Trott

Most astronomy stores will supply Baader film, as does Amazon - http://www.amazon.co.uk/Baader-Astro-Solar-Film-Sheet/dp/B004SN02TO/ref=sr_1_1?ie=UTF8&qid=1339687344&sr=8-1

Reply to Tim Trott
james siama

james siama

will a used X-ray film okay to view annular solar exclipse?

james

Reply to james siama
Perfect Astronomy

Perfect Astronomy

No it is not!

Please only use materials and instruments designed for the specific purpose for viewing the Sun!!!

Solar viewing film is not expensive and is specifically designed for viewing the sun.

http://www.baader-planetarium.com/sofifolie/sofi_start_e.htm

Reply to Perfect Astronomy

 

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