Solar Filter Tutorial

So, with the pending eclipse, I have my glasses ready and some pairs for the kids, but thought I might as well make the most of it and try and view it through the telescope. I might even manage to take a couple of basic images to commemorate. So I spent the weekend making a solar filter to use on Friday…which, judging by the forecast, will end up being used a week later when the sun can actually be seen, but I am still hoping for clear skies.

It is a very basic model, but I thought I would share my efforts here in case anyone else was thinking of having a go.

Materials were simple.

1 – Baader Solar Filter sheet – A4
2 – Corrugated Cardboard
3 – Gaffer Tape
4 – Sticky back black felt
5 – Double sided sticky-tape.
6 – Compass
7 – Stanley Knife
8 – Ruler
9 – Scissors

I also bought a 10inch Embroidery Ring to clamp it down onto the scope (I built it for a 200p Dob), but may not need it other than for extra safety as the whole thing is pretty tight when it goes on.

So here goes:

Firstly I took two, roughly 12inch square stiff carboard squares that came from two paintings I hung at the weekend and cut two circles from them, a little larger than the aperture of the scope.

Card Blanks 1

I couldn’t go “full-size” for the filter as the A4 sheet wouldn’t cover it, so I also cut a 170mm aperture from the centre of each circle – ending up with two rings that would eventually sandwich the filter material between them

Card Blanks 3

I then wrapped a 6 inch-wide piece of corrugated cardboard around the end of the scope and secured with gaffer tape to get started on the main body of the filter. I did this with 3 pieces of card to add rigidity and so that the width of the cylinder matched the diameter of the discs prepared above. I can’t give you the exact measurements as I kind of went on a wing and a prayer when doing that!

Body 1

Body 2

I then simply taped up the edges to hold everything in place. (Overseen by the chaps from Toy Story 3)

Shaping 1

When the edges were done, I then “flocked” the inside of the cylinder with two A4 pieces of felt cut in half.


flocking 2

Then on to the Solar Film. I basically laid this flat on tissue paper as per the instructions that came with the filter paper and took one of the pre-cut discs, covered it in double-sided tape…

adding film 1

…and then lowered it on to the film so that it stuck. Be careful to make sure you don’t stick it to the side with the clear protective film (or that you have carefully removed it) because, otherwise, the disc will lift away from the solar film when you lift it as it will be stuck to the protective film. I also covered the inner edge of one of the rings in gaffer tape as this would be the top ring, exposed to the elements and it would be impossible to cover once the solar film was in place.

Anyway, I forgot to take a photo at this stage, so you will have to use your imaginations I’m afraid.

Having stuck the film to one ring, I took the other ring (already covered in double-sided tape) and connected the two to sandwich the solar film in between. I then trimmed the excess.

Then it was just a matter of joining everything together. So I took the filter rings and placed them over the cylinder

top on 1

And secured everything in place

Top on 2

And then just covered the whole thing in gaffer tape to “seal” it all up

finished 1

finished 2

And there it is. It fits very snugly on the scope and seems to be doing it’s job. I still have to test it with the sun, but it blocks out the light from various halogen bulbs around the house with, seemingly, no leakage around the edge where the cylinder joins the discs. Will hopefully get a chance to test it out before Friday.

I don’t know if the filter sitting 2-3 inches away from the natural scope aperture will be a problem but I can easily adjust it after testing if it doesn’t work – I am sure it will be fine though.

It’s not pretty, but it seems to work and, if I look after it, I should be able to get some use out of it!

And I have just enough solar film to repeat (on a smaller scale) for the finder scope.

Hope that is helpful to anyone thinking about doing the same!

Just remember to check the film before using it to look directly at the sun and, if it is damaged in any way, don’t use it!


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