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Cheap and effective filters (solar)

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Picture of Cheap and effective filters (solar)
You can buy solar film (thin plastic sheets) at a very reasonable prices online. However, the sheet format isn't great for photography, telescopes or binoculars. You can by them as screw-on filters, but the cost gets a bit ridiculous and the size selection is limited.

This instructable is trivial, but that's where the beauty lies. Using cheap and readily available filter step-up adaptors and UV filters you can fit solar filters to your equipment.

  • Protects film from accidental scratches.
  • Wind protection to stop creases.
  • Holds filter flat and close to lens to stop internal light reflections that can create image artifacts.
  • Looks clean and professional.
  • Made using cheap and readily available parts.
  • Securely holds filters to reduce risk of them slipping and exposing your eyes to magnified UV.
    Important safety feature when using with telescopes or binoculars!
It is important to never scratch or crease the solar film since it might allow dangerous UV light to reach your eyes. If you mistakenly do so while following this instructable, don't try to salvage that section of film, just use a different piece.

This technique can also be used for colored gels!
 
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Step 1: Materials

You'll need a few things you can get pretty cheaply.

  • A cheap, thin "step up ring adaptor".
    Used to attach larger filters to cameras. ($1.20 on ebay)
  • A cheap, thin UV filter. ($3 each on ebay).
    You don't really need the UV protection, you just want physical glass to protect the film.
  • High quality solar film.
    Do NOT go cheap here!!!! 8x8 on Amazon is $18, but it's enough to do a lot of filters. Also, you won't have to worry if you mess up the first attempt.


Tools
  • Clean, smooth surface that you can cut on.
    You will be sliding the filter film around on it and you don't want to scratch it. Non-corrugated cardboard, felt, or paper with cardboard under it.
  • Needle
  • Razor
  • Lens cleaning cloth

Again, do not buy solar film from unknown vendors. If you get sold something that isn't really cutting out the UV, then you will damage your eyes and not even realize it until it's too late. It's not as important with digital cameras that use LED screens, but anything involving your eyes and the quality becomes critically important.


Step 2: Step-up ring adaptor

What to buy a step-up ring adaptor that is meant to fit slightly larger filters onto your camera.

My camera is 72mm, it says right on the lens.

The step-up ring adaptor is so that I can put 77mm filters onto the camera.

The solar film fits in this buffer between 72mm and 77mm. The UV filter will fit the larger size (77mm) and will hold and protect the solar film in place.

Again, solar film protection is an important feature. If you're using the filter with a telescope or binoculars. You don't want any scratches or folds in the film and the glass UV filter is there to protect the solar film.

Step 3: Trace solar film

I experimented with a bunch of ways to cut the solar film and settled on one that works for me. Please suggest alternate ways to cut in the comment.

  1. Place solar film onto a large, thick piece of smooth cardboard or paper or felt cloth.
  2. Place the ring adaptor onto the solar film
  3. Use a needle to trace the outside (77mm) of the filter onto the film.
    Yes, this will be slightly too big

You can see in my second photo that I messed up a little, but that's ok because this circle is bigger than we need.

Step 4: Cut solar film

Now that you have a circle traced on the solar film, it's time to cut it.

You'll want to cut slightly inside the circle, but don't worry. There's room for error and if it will probably be too big the first iteration.

4. Place the edge of a sharp razor just inside the etched circle. It should dig into the cardboard under the film and say there.

5. Now move the film and leave the razor in place.
This is a similar action to using a bandsaw.

6. Slide the film around to cut out the circle.

Be careful to not scratch or crease the film.

7. Once you have the circle of film, see if it fit inside the adaptor ring (It probably won't).

8. Repeat the bandsaw technique to shave off a little around the outside until it does fit.

Step 5: Clean and assemble

Final step is to place the solar film into the ring adaptor and screw on the UV filter.

Naturally, you should gently clean everything of dust first. Just be careful and DON'T use a strong blower on the filter, it will crease it.

Store your final filter in the UV filter case.
JTomM1295 months ago
I would aim for the true color filter solar material myself. And you can always sandwich two UV filters together to give the solar filter material more protection.
arikii5 months ago

Of course, a micrometer and cnc laser cutter might be the most precise way to go about this, but this works great for those of us who don't have expensive laser equipment available to us...

pavel37596 months ago

Why don't you pay attention to the huge spots on the sun?

chadn16 months ago

Will this type of solar film work for viewing an eclipse?

trophygeek (author)  chadn16 months ago
It's the same film and it works great for photography and this hack.

I plan to do it for my binoculars for the upcoming US solar eclipse in 2017.
http://en.wikipedia.org/wiki/Solar_eclipse_of_August_21,_2017

It's a good idea to plan solar eclipse trips a couple of years in advance.
chadn1 trophygeek6 months ago

https://www.facebook.com/pages/Solar-Eclipse-Viewing-Grand-Island-NE-8-21-2017/205981596088588

Thanks, I am already making plans. Come to Grand Island, Nebraska to see the eclipse. likely to have clear weather that time of year and time of day. That is why I was asking.

trophygeek (author)  chadn16 months ago

Oh, and some other comments below list sights that have high-quality solar filter sheets. You might want to check them out.

maewert6 months ago

When I was a kid, in accordance with the astronomy books at the time, I 'smoked' a glass plate by placing the glass plate over a candle's flame and moving it around until the soot was dark and uniform.... my goodness, I'm lucky I still have any eyesight left.

Nice instructable and much more safe!

trophygeek (author)  maewert6 months ago
Yikes! Yeah, I had a "wood burning kit" as a kit that was nothing more than a soldering iron. Your story makes that sound downright safe.

I was in China for the 2009 solar eclipse and the "solar viewing glasses" that street vendors were selling would damage people's eye. Their culture (at the time) was very much buyer-beware. Good thing is was clouded over for most of the country.
gingertux6 months ago

You can use a good set of scissors to cut the solar film out. If you are using corrugated cardboard, the change in density between corrugations can cause the razor blade to slip and give an irregular edge. Also not as safe.

trophygeek (author)  gingertux6 months ago
Yeah. I suggested felt fabric and when I said cardboard, I was thinking non-corrugated. I'll update the instructable to be more clear.

High quality scissors can be used, but I always struggled to not crinkle the solar film while handling it. Placing it on flat surface seemed to work better for me. But I don't have a lot of scissor cutting experience.
alzie6 months ago
Great idea.

Also, consider the Baader solar film.
http://www.baader-planetarium.com/sofifolie/sofi_start_e.htm

Ive used this stuff telescopically, and
it works very well.
trophygeek (author)  alzie6 months ago
That site has a scary instructable for using cardboard and tape to "secure" filters onto a pair of binoculars.

http://www.baader-planetarium.com/sofifolie/bauanleitung-bino-en.pdf (PDF)

Would be nice if they updated it to use the technique I described here.

BTW, I put this instructable under a public domain license. Sites can either link to it or just create their own white paper based on it.
alzie trophygeek6 months ago
Actually, the card board n tape method works pretty well.
You make a card board cup that
mates to your instrument with a friction fit.
Also, since youre looking Up at the sun,
gravity helps keep the filter on your instrument.
Ive made 2 of these,
one for my 3" refractor and
one for my 8" reflector.
The baader film works very well.
trophygeek (author)  alzie6 months ago
Thanks! It's good to have choices since many sellers are perpetually out of stock.

My filter usage is with OLED viewfinder cameras, but I plan to do one for my telescope and am looking for a better source than Amazon.
King of Clubs6 months ago
This is one of the best solar films.
trophygeek (author)  King of Clubs6 months ago
Good to know! Thanks.
Much better than the Thousand Oaks filter.
AngryRedhead6 months ago
Clever, fellar!
trophygeek (author)  AngryRedhead6 months ago
Thanks!
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