How to SAFELY View the Sun to See a Solar Eclipse and Search for Sunspots.

Intro: How to SAFELY View the Sun to See a Solar Eclipse and Search for Sunspots.

I am going to show you how to view the sun using several indirect viewing methods, ranging from looking at shadows on the ground, to projecting through a telescope. I have recorded a video that explains how solar projection works, and provides several different examples of how to project the sun.

It is easy to think the best way to look at the sun is through glasses with special lenses, but it isn't, for several important reasons.

1. Some "eclipse glasses" are not actually safe for solar viewing - some of the ones I purchased online were just recalled by Amazon.
2. The filter discolors the sun, giving it an orange color - it actually looks white.
3. I think we assume the image is better because we are looking directly at the sun, but the image is really small. You can achieve bigger and clearer images through indirect viewing methods.

The materials you will need for this method are as follows:

• A thumbtack
• Cardstock
• Cardboard
• A tree
• A cheap refractor telescope. Here are a few that work:
  • Telescope I used - $30 telescope
  • a cheaper one: $11 telescope
  • another cheaper one: $27 telescope
  • a slightly more expensive one: $38 telescope

STEP 1: Pinhole Projection

All you need to view the sun is a small pinhole, that you can poke into an index card or a piece of card stock. Punch a hole in the card, and hold up in the air. Catch its shadow on another card. The light spot you see in the middle of the card is an image of the sun. You are seeing an actual projection of the sun. It is similar to how when you look at a projector bulb it appears very bright, but you can see an image when you see it land on a screen. The same thing is happening here. You may notice that the eclipse appears to be rotated 180 degrees. This is an effect that occurs when the light traveling from the sun passes through a pinhole.

STEP 2: Pinhole Projection (using a Box)

You can get a slightly clearer projection using a cardboard box. If there are holes in the corners or sides, cover them with tape. Then, punch a hole in the box, and point the side with the hole towards the sun. Look for the light that appears on the far side. This is the image of the sun on the back of the box.

STEP 3: Pinhole Projection (using a Tree)

You don't actually need anything to view the sun or look at an eclipse. Tiny gaps between leaves in trees act as pinholes, and so you can see the sun any time you look at the shadow of a tree on the ground. When an eclipse happens, the tiny dots turn into tiny crescents.

STEP 4: Telescope Projection

The best way to get a really clear image of the sun is to project it using a telescope. (Never look at the sun directly with a telescope). This only works with cheap telescopes, more expensive telescopes can be damaged if pointed directly at the sun. But with the right one, you can point the telescope straight at the sun, and catch its projection on a piece of cardboard or foam board. The key to aiming the telescope at the sun is to make its shadow on the ground as small as possible. The image is very clear, and you can get it to about 16" in diameter. It is big enough that you can actually see sunspots on the surface of the sun, and should be a pretty incredible way to view a solar eclipse.

Comments

[RavenN12]

If I were to tape one of the lenses over on a pair of binoculars, would that work the same as a telescope?

[More Than the Sum]

It works the same with binoculars, i don't even think you need to tape over them.

[cosmicknight782]

Another way is to smoke glass, so that they become cloudy and dark, then look through them

[More Than the Sum]

Be careful looking at the sun this way, just because it looks like it blocks enough sunlight doesn't mean it actually does!

[cosmicknight782]

It does, I've tried it a couple of years ago.

[rycki1138]

Will the refractor telescopes you have mentioned above get too hot in the sun and will it damage the lenses of the telescope? I ordered one through Amazon to try the projection method, but was just wondering if the sun would crack the lenses if it gets too hot.

[More Than the Sum]

Thats an interesting question. I'm not sure. The light is most concentrated just before the eyepiece, so that is the area where something could go wrong - there is a mirror there, so if anything were to be damaged, it would be that. If you are concerned, you could try giving the telescope periodic breaks to cool, or maybe even wrapping an icepack in that area. As a reference, this suggests that anything with a lens smaller than 4" should be fine to point at the sun: http://www.skyandtelescope.com/astronomy-news/how-...

Please let me know how it goes, and also share some pictures! https://twitter.com/aaron_stafford

[rycki1138]

Thanks for the suggestions and for the link. The telescope is supposed to arrive on the 17th of August. I'm going to test it to see if how it works projecting the sun onto a card before the day of the eclipse to see how it works. It's not an expensive one, I got the $11.40 one from Amazon, but I'd still like to use it for looking at the moon and stars even after the eclipse. So I don't want to ruin it right off the bat. Thanks again.

[More Than the Sum]

To protect the mirror, you could also try removing the 90 degree elbow and stick the eyepiece in so it is pointing straight back, then your projection would be on the ground below the telescope.

[vbuncha1]

As for me this one is the best!

[1GearyMOM]

What is it and how do you use it?

[rycki1138]

Now that I think about it, 3.5 Floppies do have a small square hole in one corner that could possibly project the sunlight onto the ground or on a sheet of white paper or white board to view like the pinhole box mentioned above.

[rycki1138]

I can tell you what it is, but not what it's used for to look at a solar
eclipse. It's an obsolete 3.5 inch floppy disk for a computer. They
don't use them anymore because they only hold 1.44 mb of information.
Back in the 90s these could hold entire programs (including early
Windows installation), but have since been made obsolete by bigger hard
drives and larger capacity storage drives.

[jeandan]

You said that viewing the sun with an expensive telescope will ruin it. Will it not also ruin cheap telescopes. If the answer is No- why are just expensive ones ruined and not cheap ones?

[More Than the Sum]

There are a couple of factors. One is that you are concentrating sunlight at a focal point inside the telescope near the eyepiece. If it has a powerful magnification, the telescope can get to hot, and sustain damage. If it is a reflector telescope, the mirrors inside can be damaged from the magnified sunlight as well.

[TheOldGrouch]

If you happen do do welding, you (should) have a pair of welders goggles or a helmet. They should certainly do the trick as they are able to protect you from the blinding effects of the welding arc, which is most likely at least as bright as the sun. Also, I've done the pinhole viewer during the eclipse that crossed Virginia Beach, Va. back in 1970

[ericlawrence]

NASA recommends only #14 or higher welder's glasses.

[wfidrock]

Actually NASA recommends #12 or higher, saying #13 is best (but harder to find) and #14 is a little too dark, but usable.

I purchased replacement lenses (should arrive tomorrow's mail) from an online welding supply company, Shade #13 lenses, 2" by 4.25" and will use them to make a cardboard viewer (think bottom of a cereal box, cut to fit snugly around eyes and nose, lens at the end sealed with duct tape).

The replacement lenses only cost about $3 each (I bought 5) including shipping and handling and after this years eclipse I will dismantle my viewers and store the glass lenses for the eclipse on April 8th, 2024 (which will be a total eclipse for me in Austin, TX)!

[ericlawrence]

I haven't done any welding since college, so I can't speak from my own experience, but this NASA page specifically calls for #14: https://eclipse.gsfc.nasa.gov/SEhelp/safety.html

[wfidrock]

And this (later, more up-to-date 2017) NASA page (the one you reference is adapted from a late 1990's page) is what I was referring to:

https://eclipse2017.nasa.gov/safety

scroll down to section "Additional Safety Information, Viewing with Protection":

Viewing with Protection -- Experts suggests that one
widely available filter for safe solar viewing is welders glass of
sufficiently high number. The only ones that are safe for direct viewing
of the Sun with your eyes are those of Shade 12 or higher. These are
much darker than the filters used for most kinds of welding. If you have
an old welder's helmet around the house and are thinking of using it to
view the Sun, make sure you know the filter's shade number. If it's
less than 12 (and it probably is), don't even think about using
it to look at the Sun. Many people find the Sun too bright even in a
Shade 12 filter, and some find the Sun too dim in a Shade 14 filter —
but Shade 13 filters are uncommon and can be hard to find. The AAS Reputable Vendors of Solar Filters & Viewers page (link is external)
doesn't list any suppliers of welder's filters, only suppliers of
special-purpose filters made for viewing the Sun.To find out more about
eyewear and handheld viewers go to https://eclipse.aas.org/eye-safety/eyewear-viewers (link is external).