Make a Solar Filter for Your Camera or Binoculars

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Introduction: Make a Solar Filter for Your Camera or Binoculars

About: There are some things you should just NEVER do.....

Make a Solar Filter for Your Camera or Binoculars

The next Total Solar Eclipse over the Continental United States will be April 8, 2024. At that time a partial eclipse will be visible over most of North America. If you want to take some photos of the partial eclipse you will need a special filter for your camera. I made this filter for my camera and similar ones for my binoculars for the August 21st 2017 Solar Eclipse which was amazing and especially spectacular when viewed in the path of totality. Google '2024 Eclipse' for websites to learn more!

To safely view and photograph a partial eclipse you need special eclipse glasses or filters. This Instructable shows how to make a nifty filter for your point-and-shoot camera or for binoculars.

This filter is not only good for viewing partial eclipses, but also for viewing the sun's disk along with sunspots.

I took some photos of the sun and noticed sun spots. I looked at NASA's Solar Dynamics Observatory website and saw the same sun spots!

Supplies

Solar Eclipse Glasses

3D printed filter holder

3D printed filter cutting template

3D printer and software

Box cutter or razor knife

Calipers (to measure camera lens barrel)

General Purpose Adhesive (glue)

Toothpick to apply glue

Camera or Binoculars wanting the filter :-)

Block of wood to cut on

Step 1: Start With Certified Eclipse Glasses

The filters used in this project are from inexpensive Solar Eclipse glasses that have been certified as safe for direct solar viewing. Do not use any type of glasses or filters that do not bear a certification for use to directly view the sun. These filters are black on both sides. Not silver. There has been some concern over filters that are silver on one or both sides. Look for certification information on the glasses.

Also note that the filter MUST be installed on the lens closest to the sun. It is is NOT SAFE to have the filter located next to an eyepiece or just in front of your eye. The filter must be installed so that it filters the sunlight as it enters the camera or binocular.

Some cameras have a separate viewfinder for composing your image. This filter arrangement will not provide safe viewing through a viewfinder. Do not look through the viewfinder eyepiece when using this filter.


Step 2: Measure Your Camera or Binocular

Measure your camera or binocular to determine the size the filter needs to fit onto. You will use this information to design a 3D printed filter holder that will fit snugly onto your camera or binoculars.

Step 3: Design a Filter Holder

Use Fusion 360 or a similar program to design a filter holder that will fit onto your camera or binoculars.

You need to take into account the diameter of the lens tube that you measured in the previous step and allow a slight gap between the finished part and the camera.

I designed in some tabs with gaps on each side into the perimeter of the filter holder to provide friction fit under tension when the filter holder was slipped over the camera or binocular lens.

On the inside of the filter holder is a rectangular recess that is designed to hold a piece of filter material cut from the eclipse sunglasses.

You will need to 3D print the filter holder. In addition to the filter holder it is helpful to design and 3D print a filter template that matches the recess for the filter in the filter holder. This template will be used when cutting out the filter material from the eclipse glasses.

I have attached example files of the filter holder and filter cutting template.

Step 4: Cut Out the Filter

Cut out the filter from the eclipse glasses. The filter material that is cut out should fit into the recess in the filter holder.

You can use the template to cut out the filter material if you chose to 3D print one.

Step 5: Install the Filter Into the Filter Holder

Check fit the filter material into the filter holder. Trim if needed. Note that the filter must fit edge to edge into the filter holder. There cannot be any gaps or blinding sunlight will slip past the filter.

Using a toothpick apply glue to the recess in the filter holder and place the filter material onto the glue to fasten it securely into the filter holder

Step 6: Install the Filter Onto Your Camera

Install the filter holder, with the filter securely mounted, onto your camera or binoculars.

(Remember to make two filter assemblies for binoculars ;-)

Make sure to only look into your binoculars if the filters are installed.

Enjoy!

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    7 Comments

    0
    Khovet1
    Khovet1

    1 year ago

    Do you have a source for the glasses?

    0
    wannabemadsci
    wannabemadsci

    Reply 1 year ago

    Just Google "eclipse glasses" or go to Amazon.com and search for "eclipse glasses" and you will find plenty of inexpensive cardboard and filter eclipse glasses. As I mentioned, only use ones that are certified for direct view of the sun.

    0
    arpruss
    arpruss

    1 year ago

    I wouldn't do this with binoculars! The eclipse filters are rated for naked eye sun viewing. But the binoculars will gather several orders of magnitude more light than the naked eye, so one is apt to be far beyond the safety ratings.
    There are proper solar telescope filters one can buy and cut to size.

    0
    ElectroFrank
    ElectroFrank

    Reply 1 year ago

    Binoculars are gathering light from a narrower angle, therefore smaller binoculars provide a dimmer image than the naked eye would see. But what you say might apply to larger binoculars.

    0
    arpruss
    arpruss

    Reply 1 year ago

    I'm afraid not, at least not for binoculars whose field of view is big enough to contain the whole solar disk. Typical small binoculars have a field of view more than sufficient to contain the sun: the sun takes up 0.5 degrees of sky, and the true field of view of typical small binoculars is at least 7 degrees.

    The eye pupil gathers light from at most an 8mm diameter disc, and only a 2mm disc in bright light. Pretty much the smallest diameter of commercial binoculars is 20mm, and 30mm is much more common. Since the light-gathering area is proportional to the square of the diameter, the 20mm binoculars will gather between 6 and 100 times as much light as the naked eye will, as long as we're dealing with an object that fits completely into the field of view--which the sun does.

    You can safely test how much brighter the images from binoculars are--even really small binoculars--by looking at the night sky. You will see a lot more stars that are too dim to see with the naked eye. This has nothing to do with the magnification (stars other than the sun are so far away that they are basically a point for any amateur equipment), and everything to do with the fact that the lenses are gathering light from a much larger area.

    Proper telescope-rated solar filter material is not expensive: https://agenaastro.com/baader-astrosolar-visual-filter-film-nd-5-eco-sheet-2459286.html
    And binoculars are just a pair of telescopes.

    I am sorry for going on and on about this, but this is a very important safety point. DO NOT USE SOLAR FILTERS NOT RATED FOR A TELESCOPE OR BINOCULARS WITH A TELESCOPE OR BINOCULARS.

    Of course, even with telescope-rated solar filter material, the material needs to go in front of the objective like in this Instructable (rather than behind the eyepiece, where it will be burned away).

    0
    msameer39
    msameer39

    1 year ago

    Very nice idea.
    I have used the solar filter which was made up of some dark glass material (3mm thick) on my telescope and it got cracked by the Sunlight. I will strongly suggest everyone to be cautious with converged sun rays.

    0
    ElectroFrank
    ElectroFrank

    Reply 1 year ago

    That's why (as the author stated) the dark glass must go in front of the objective lens, not over the eyepiece. It is designed to absorb light, so if bright light is focused on it, that part will overheat, expand and crack. In front of the objective lens, it is warmed evenly by the light, so does not crack.