2017 UPDATE: At the time I wrote this post, the Transit of Venus 2012 was just around the corner, and I had no resources to safely observe it, so I found this method and it worked just as fine. I and my friends had no adverse effects on our eyesights because we did take several precautions (covering almost entire aperture of the telescope, repeatedly checking the filter and tape). Also, it was very hazy that day so the sunlight didn’t enter the telescope with full intensity. It is advised to never use makeshift arrangements for solar observation.
You want to observe the Sun, Sunspots, Venus and Mercury Transits, Solar Eclipses, but don’t have a Solar Filter? Here is how you can make use of adversity and make a Great to Go Solar Filter within a few minutes.
Items needed
Black glass used by Electric Welders.
Eyepiece of your telescope or binocular.
Tape.
Nothing else.
First thing you need is a black glass that Electric Welder (The guy which joins the pieces of metals together with help from excited electrons) uses.
It looks something like this:
Black Welding Glass
Make sure its surface is perfectly and evenly coated. If there is any imperfection, or coating is missing from some point (even if its size is of a pinhole) RETURN IT ! and ask for a new piece. Mine was Made in Germany and it was of Number # 10. Try it out at an incandescent light. The light must appear too dim so that you can comfortably see it. Next, try it out at the Sun.
If its too dim, then you have the right thing. Under the sunlight, carefully examine the surface of glass before proceeding for any imperfections.
Next thing I did was to get the glass cut in circular discs. The size of disc was the same of the eyepiece barrel.
Eyepiece without filter
Place the disc above the eyepiece barrel from the end that goes inside the telescope. It will look like this.
Eyepiece with filter
Tape the disc with eyepiece firmly so that it does not move even by 1 mm. Your hanky panky Solar Filter is now ready.
You can also cover your binoculars eyepiece or objective lens with same procedure. I tried it out on binocular objective lens and it did work comfortably, but I don’t know what are the results if you use it at eyepiece. You can always experiment and try to get a safe picture at paper first to check if no harmful light is coming out of it.
Note: It is advisable, that you do not make use of full aperture of your telescope, so as to be on a safe side always. Even a pinhole can give you a great image of the Sun since it is too bright. Also, keeping your telescope’s aperture covered totally will help your eyepiece, secondary, and primary mirror in remaining cool.
For this, you can cover the entire aperture of your telescope with a black chart, and then make a small off-centre pinhole in the chart. (Off-centre hole is necessary. If hole is made in centre, the light would be blocked by the secondary mirror). Now slide in the eyepiece and point the telescope to the Sun.
Pointing will be done by using shadow method rather than looking inside the Eyepiece. When shadow of your telescope becomes round as the aperture of your telescope, its looking at the Sun.
Now try to get a picture of Sun on paper to ensure that no intense Sun rays are coming out of the eyepiece.
Next, stand far away from the telescope and see if the eyepiece is dark and not Sunlight is appearing inside it.
Watch the Sun from the eyepiece and focus it.
Yayy so now you can observe all Solar Phenomena 🙂
P.S: I have made such a filter and am very consistent with it. Considering that I found correct glass and used all the safety precautions that are needed to test the telescope before going Solar.
Make sure you examine the glass, the eyepiece, and the image thoroughly before directly looking in the telescope. The risk of permanent blindness.
Mario, you are right. It is indeed not recommended and dangerous. But I used it with precautions by covering the aperture of telescope with thick black paper to keep the light entering the telescope at minimum level.
It still looks risky 🙁
Not recomended, any telescope filter must be adapted to the telescope light entrance, never to the eyepieces, its too dangerous
Mario, you are right. It is indeed not recommended and dangerous. But I used it with precautions by covering the aperture of telescope with thick black paper to keep the light entering the telescope at minimum level.
Sir. BILAL Will it be safe to observe sun by using the filter u have suggested with the black pape on the front lens of my refractive telescope?