Fun with the sun
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| Sunspots of February 3, 2026 |
Okay, hold on a sec. Let me be perfectly clear: The sun is the most dangerous celestial orb in the sky, and I DO NOT want you to think that my title "Fun with the sun" means that you can treat the sun, er, lightly. NEVER look directly at the sun with your eyes, not even for an instant!
You know that guy, Andrew Huberman, who says you should go outside immediately after waking up in the morning and look in the general direction of the sun to reset your sleep cycle?
DO NOT FOLLOW THAT ADVICE!
Make no mistake. The sun is no toy! And, sure, we have all accidently looked directly at the sun from time to time, giving us black spots in our vision for the next several minutes. Experiencing that once should be enough of a warning for you to NEVER DO THAT AGAIN!
Sunglasses don't protect you, either. Do not be misled. Sunglasses were not designed to let you gaze upward at the sun. Not even during partial solar eclipses. Too much harmful radiation can still reach your eyes unless you're looking through #14 welder's glass or Baader safety film (the stuff used in those cardboard solar eclipse viewing glasses).
Galileo frequently looked at the sun through smoked glass, and that didn't protect his eyes well enough, either. He went blind in his old age, most likely from his solar studies.
But I'm not talking about subtle eye damage. I'm not talking about the kind of eye damage that comes back to haunt you later in life.
I'm talking about the right now and instant eye damage that comes from looking at the sun through optical equipment, like binoculars and telescopes, without proper solar filters.
You may recall some time in your life experimenting with magnifying glasses and sunlight. You can light paper on fire using a magnifying glass and sunlight. Yes! And that's just a tiny little magnifier. If you can start a fire with a magnifying glass, maybe now you can imagine the kind of fire that you can start with a powerful telescope!
No kidding! The cone of sunlight that's brought into focus on your eye by an unfiltered telescope is like a blow torch. It will literally burn your eyeball out of its socket!
Some amateur astronomers like to demonstrate the hazardous nature of the sun at public sun-gazing parties. It's very effective! They will aim an unfiltered telescope at the sun and hold a grape just above the eyepiece. When you see that grape cook instantly, it will teach you a lesson you'll not soon forget!
Unfortunately, in the light of day, you can't see the dangerous cone of light coming up out of the eyepiece. It's something that you must maintain awareness of at all times when setting your telescope up during the daytime hours to view the moon or distant terrain, or even birdwatching. Do not leave young children unattended with a telescope out in the back yard when the sun is up.
Lastly, while it is fun to share solar viewing with friends and family, you must be over-cautious about everything! You do not want to be responsible for ruining someone else's eyesight (or your own)! Warn everyone in attendance against even casually looking up at the sun while they're standing around waiting for their turn at the eyepiece. Have parents keep an eye on their children to make sure they are not sneaking peeks at the sun. Also, you must make sure that you are using a proper and safe solar filter (do a Google search of "are full-aperture solar filters safe"). But that comes with the additional requirement that you must take care to inspect your solar filter for signs of damage or pinholes prior to use. And by all means, when you go out there to get the telescope set up, do it alone! Don't risk getting distracted with searching for a component or plugging in cables or something, while others might be tempted to do something unsafe before you can stop them. Have everything set up and safe BEFORE you invite others to join you.
So having spoken of the dangers, let's get back to the fun part!
There are a couple of completely safe methods of using a telescope for solar viewing. Well, "completely safe" if you use extreme caution!
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| Solar projection using an unfiltered 8-inch Newtonian Reflector |
The first method is called projection. You aim the telescope at the sun and put a white card a couple of feet from the eyepiece. The sun's image, with all its sunspots, will be projected onto the card. Note that this leaves the dangerous blow torch exposed to the public. Give clear instructions to your fellow observers as to where it is safe to stand, look, and touch, and where it is unsafe to stand, look, and touch. Be watchful of the group at all times and keep people and body parts away from the eyepiece during solar projection. Also bear in mind that the sunlight passing through an unfiltered telescope can cause extreme heating within the instrument. Parts can melt, come unglued, or crack and be destroyed. For this reason, only simple Newtonian reflectors and refractors should be used for projection of the sun's image. Do not use the projection method with catadioptric telescopes such as SCTs or Maksutovs.
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| Astrozap Baader full-aperture solar filter on my 11-inch SCT |
Another safe way to view the sun through a telescope is by using a full-aperture solar filter. Buy your solar filter material (or a commercially-made filter cell that fits specific telescope apertures) from a reputable telescope dealer. Remarkably, a thin sheet of Baader solar film that completely covers the front end of the telescope, is all you need.
Baader solar film blocks more than 99% of the sun's radiation, making the eyepiece view perfectly safe, and keeping the interior of your telescope cool. However, you must be careful with the Baader film. Inspect it before each use to make sure there are no pinholes in it. And you must attach the Baader film securely onto your telescope, so that it can't fall off or get blown off by a gust of wind.
I purchased an Astrozap Baader full-aperture solar filter for my 11-inch SCT. It cost around $150 US. The filter is comprised of a sheet of Baader solar film glued onto a metal cell that slides onto the front of the telescope tube. Three nylon screws secure the filter to the telescope.
This kind of solar filter produces what is called "white-light" solar viewing. The sun's visible wavelengths are seen through the eyepiece, producing a neutral white disk with dark sunspots, as seen in the photo at the top of this page.
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| Lunt 50 mm Hydrogen-alpha Solar Telescope on a Celestron 4SE mount and tripod. |
Solar prominences on the sun's limb cannot be seen with white-light filters. Those features require a different type of filter called a Hydrogen-alpha solar filter (not to be confused with the H-alpha filters that astrophotographers use to photograph nebulae at night). Hydrogen-alpha solar filters are very expensive! Even a small 50 mm aperture Hydrogen-alpha telescope costs more than $1000 US. I have a Lunt 50 mm Hydrogen-alpha telescope (shown above), and I enjoy the views through the eyepiece, but I haven't figured out how to get decent pictures with it yet.
Whether you're using projection, a full-aperture white light filter, or the Hydrogen-alpha method of observing/imaging, the sun presents a unique challenge for aiming your telescope. For all other celestial targets, like the moon, planets, and deep-sky objects, you can rough-aim your scope by sighting along the tube and then narrowing your search by using red-dot finder or an 8X optical finder scope with crosshairs. But, as mentioned previously, you DO NOT want to aim your telescope at the sun by sighting along the tube or by looking through your finder scope! And certainly, DO NOT use your finder to look at the sun, unless it's protected with a full-aperture filter, too!
So, how do you safely aim your telescope at the sun?
Tele Vue's "Sol Searcher" is the most elegant solution. Normally, when you're aiming a telescope at a celestial object, you start by sighting along the telescope tube. When it looks like the telescope is aimed at the object, you next look into the finder scope and center the target with your crosshairs or illuminated reticle. But the Sol Searcher allows you to find the sun by literally turning your back on it! The picture below illustrates how to properly use the Sol Searcher, by looking at it from the front end (sunward facing end).
The Sol Searcher consists of two opaque disks of about 1-3/8-inch diameter, spaced about 2 inches apart. Very simple. You could probably build one yourself, if you have the skills and the right tools and materials. But the Sol Searcher costs only $50 US. Why reinvent the wheel?
The alternative way to aim your telescope at the sun without looking at it, is a safe method that I've used for years. This method is based on the assumption that when your telescope is perfectly pointed at the sun, its shadow on the ground will be its smallest possible footprint. The shadow of the telescope's optical tube, for instance, will have the smallest diameter. Thus, aiming your telescope can be done with your back to the sun, while you observe your telescope's shadow on the ground. Start by using a very low-powered eyepiece, because you'll increase your chances of finding the sun quickly by using an eyepiece that gives you the largest field of view. (VERY IMPORTANT: Remember to install your telescope's full-aperture solar filter BEFORE looking into the eyepiece!)
In practice, this method of aiming your telescope at the sun relies heavily on good luck! Some days, I have used this method and landed the sun in the eyepiece on the first try. But then on other days, I'd try my best to make my telescope's shadow the tiniest footprint, and when I looked in the eyepiece, the sun was nowhere to be found. I'd sometimes spend as much as 10 minutes, moving the scope back and forth, up and down, searching for the sun before achieving success. It can be very frustrating. The Sol Searcher, by comparison, is straightforward.
When you install the Sol Searcher the first time, you will need to use the alternative method in order to align the Sol Searcher. After getting the sun centered in the eyepiece, adjust the screws on the Sol Searcher so that the tiny solar image projected on the rear screen is perfectly centered. You can rest assured that this will be the last time you need to use the alternative solar aiming method! Thereafter, once you get the sun's disk inside that translucent screen on your Sol Searcher, the sun is guaranteed to be in your telescope's eyepiece field of view. And you'll get it done quickly, easily, and safely! I think the Sol Searcher is worth every penny of its $50 price tag.
Oh, and one more thing: When setting up your Go-To telescope mount during the day, you'll need to use the sun and the "Solar system object" method of alignment. MAKE SURE to install your telescope's full-aperture solar filter FIRST! Some mounts require that you perform an additional step, and that is by going into "Utilities" and enabling "Allow using the sun for alignment." Once again, I must reinforce my warnings by saying DO NOT enable the sun setting unless you fully understand the dangers, and you know how to safely aim your telescope at the sun without looking at it. Telescope manufacturers have that setting disabled by default because they don't want to be responsible for allowing unwary telescope users to align on the sun without a proper solar filter. So, if you don't see the sun your list of solar system alignment objects, and if you are fully aware of the dangers, look for an "Allow using the sun" setting in one of the menus under Utilities. If you don't have a Sol Searcher (or similar product), using the alternative method of aiming your scope at the sun (that I described above) is, unfortunately the only way to safely complete the alignment step of your Go-To mount. Some people might be tempted to choose Venus instead, but again, that's going to increase your chances of eye damage. Even at times of greatest elongation, the sun will be in full view while you're trying to aim the scope at Venus.
Funny story about my Sol Searcher purchase.....
As I mentioned earlier, I have a Lunt 50 mm H-alpha telescope, which I use with a Celestron 4SE mount and tripod. Finding the sun with that setup without a solar finder was getting more and more difficult and frustrating. When I found out that Lunt sold the Sol Searcher finder, I immediately placed an order. Lunt is just across town from me in Tucson, AZ, so I chose "in-store pickup" as my delivery method.
For as long as I can remember, the word "Sol" as a name for the sun has been pronounced "SAUL" (rhymes with "PAUL"). You'll recall that a day on Mars is referred to as a "sol." NASA videos talk about how many "sols" (which they pronounced "SAULS") a certain rover has spent on the surface of Mars. So, when I saw that Lunt was selling a "Sol Searcher," I thought it was pronounced "SAUL Searcher." As a finder scope that's designed only for the sun, it was quite natural for me to think of the pronunciation as "SAUL Searcher." And Goodness knows, I've spent many an hour searching for Ol' Sol in plain sight with my telescope, without success!
Imagine my surprise when I got a call one day from Lunt, informing me that my Sol Searcher was ready for pickup. I wasn't available when they called, so I got a voice mail. When I listened to the message, it went, "Hi, John. This is [so-and-so] at Lunt Solar Systems. I'm just calling to let you know that your 'Soul Searcher' is ready for pickup."
Soul Searcher??!!!
Never once did I ever think of "soul searching" when I saw the name "Sol Searcher"! I laughed out loud at the obviousness of the pronunciation. I kicked myself for never having recognized the pun!
Wow! Okay. Back to the original topic of this post: Fun with the sun! What is there for you to see?
I am sorry to report that the best solar viewing is, unfortunately, by using the far more expensive Hydrogen-alpha solar telescopes. There's always something to see in Hydrogen-alpha light. Those beautiful hoops of plasma on the solar limb known as solar prominences are always available for you to study, as are solar flares, filaments, and sunspots on the sun's so-called surface (remember, it's a ball of plasma that has no hard surface). Without a Hydrogen-alpha telescope, the only way to see prominences is during total solar eclipses. But Hydrogen-alpha telescopes are not only expensive; they require a little more tweaking than other types of solar filters. The learning curve is a wee bit steeper.
When using a white light solar filter, fun with the sun is limited to three activities: observing sunspots, solar eclipses, and transits. Let's discuss these for a minute.
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| Partial solar eclipse of October 23, 2014 |
Solar eclipses over your back yard are extremely rare! You might witness a couple of partial solar eclipses in your lifetime, if you're lucky. You can increase your chances of seeing a partial solar eclipse if you pay attention to the news and travel to a location where the eclipse can be seen. But if you're waiting on a local one that you don't have to leave home to see, then you're in for a long wait. Possibly decades.
Transits are even more rare! There are two types of transits: Venus transits and Mercury transits. They occur because Venus and Mercury are the only two inner planets. On rare occasions, Venus and Mercury can pass exactly between earth and sun, so that we see their silhouettes against the solar disk. Mercury is quite small, so you need a telescope to see it. Venus, during a transit of the sun, is large enough to see with your naked eye (and solar filter, of course), but it's a more pleasing view with a telescope. Not that it matters. We won't see another one in our lifetimes!
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| Mercury transit on November 11, 2019 |
Of the two types, Mercury transits occur more frequently because of Mercury's great speed. It orbits the sun much faster than Venus, creating more opportunities for a transit than Venus does. We could see as many as 13 Mercury transits in a century. But Venus transits happen less than once in a hundred years! They come in pairs, four years apart, and then take more than a hundred years to occur again. The last Venus transits came in 2008 and 2012. The next ones won't be until 2117.
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| Venus transit on June 5, 2012 |
Since eclipses and transits are so rare, fun with the sun using white light filters is usually restricted to viewing sunspots. Sunspots are interesting because they change slightly from day to day. The sun rotates counterclockwise on its axis, causing sunspots to appear on the left (east) side and drift westward a little bit each day. It takes 25 days for one solar rotation. Additionally, sunspots are known to follow an 11-year pattern of sunspot minimum (very few if any sunspots) to sunspot maximum (when sunspots are visible nearly every day). We're just past maximum, so we'll see fewer and fewer sunspots during the next several years until we reach minimum. The next maximum will be around 2034.
I guess what I'm trying to tell you is that the time to have fun with the sun is NOW!
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