When I was observing way back when I was just a dumb teenager, I was extremely lucky that I didn’t permanently blind myself by melting my eyeballs. Or by melting my telescope, either one. Because back then, I did a little solar observing – without a solar filter. How was that possible? You can do it by the projection method.
At this point, I have to insert the standard warning: don’t try this at home. The projection method is incredibly dangerous, both to your telescope and more importantly, to your eyeballs.
With the projection method, you simply point your unfiltered scope directly at the sun – more on how to do that in a bit – and the image of the sun will come out of the eyepiece to be projected on whatever you like – usually a piece of paper held about a foot or so away. In this way, you can observe the sun without the sun burning through your retina and into your brain.
I was, however, one of those kids who would try something – even something insanely dangerous – just once, to see what it would do. For example, I would light a firecracker and hold it in my hand until it exploded. Again, another thing not to try at home. It is a wonder I didn’t even take just a quick peek through the eyepiece to look at the sun directly myself. Perhaps the reason I didn’t ever do this was the fact that the sun would burn a hole right through the piece of paper if I held it within an inch of the eyepiece. Which I duly checked out, just for, y’know, the sake of a full understanding of the phenomena.
An eight-inch wide sun on a piece of looseleaf paper is pretty big. You can see all the sunspots and the granularity of the surface. But what about making that projection even larger? Well, sure! Back then, I observed the sun off of the back deck of my house, which had a little roof over it. This meant that even though the sun was shining brightly outside, it was still relatively dark inside. Especially with the blinds drawn. What about projecting the sun inside the house?
Well, it took a little doing, rotating the scope – an 8-inch Newtonian – in its cradle rings so that the focuser and eyepiece were pointing inside the house. But the result was that the telescope projected a 5-foot wide sun on our white kitchen wall! Sunspots as big as my head! Pretty neat stuff.
The real mystery of the whole operation was how I didn’t melt the scope, or crack the mirrors, or the eyepieces due to heat stress. Sunlight coming through a telescope will burn a hole through a piece of paper, or your eyeball, for that matter, because it is concentrating the full intensity of the sun onto a tiny spot – just like a magnifying glass will burn ants. Which I never, ever did. Feet are much more efficient at wiping out entire ant colonies. But the point is, the eyepieces at least, and probably the secondary mirror as well, were getting extremely hot. I have no idea what kind of glass the eyepieces were made of back then, but it is a wonder that they didn’t crack from the intense heat.
So, 35 years after my teenage misadventures with the sun, what better object to look at from light-polluted Manhattan than the ultimate light-pollution source itself? I hadn’t seen the sun in all that time, with the sole exception of the incredible Venus transit in 2012, when I was concentrating just a bit more on the inky black sphere crossing the face of the sun than the sun itself. I decided to pick up a solar filter from Amazon: the Levenhuk 127mm solar filter, with Baader solar film in it. I had read that just using black polymer film wasn’t quite up to snuff, but that Baader film was the way to go.
Well, the Levenhuk filter is terrific. It looks exactly like the dust cap that came with my scope, except the middle 100mm of the cap is punched out and covered with reflective film. It fits right onto the scope just great, just as snug as my dust cap. Spring has finally sprung, so I took the scope out the other day when it hit an astonishing 46 degrees. Of course, the problem is, how do you point your scope at something that you can’t even look at with your own eyes? Well, it’s fairly easy to point the scope generally in the right direction. After that you can move it around a little, up and down, left or right, to minimize the area of the scope’s shadow. But that wasn’t enough to get the scope on Ol’ Sol.
Fortunately, the mount for the ST-80 has iron sights – two little round holes that are lined up and pointing at what the scope is pointing at. Of course, even there, you still can only get it just so close before you’re looking right at the sun again. But that’s close enough so that when you look through the eyepiece, you can see the glare from the sun entering the scope and move it accordingly.
The solar filter worked perfectly. But the sun had a lot less activity on it than I remember. Of course, that didn’t stop me from snapping some pics:
Ignore the mottling in the upper left and right – that’s some artifact of the photographic process. In other words, my lack of ability to take a good picture. But four lousy sunspots? That’s it?
Apparently, for some bizarre reason, the sun is in some weird solar minimum lately. Normally, the sun’s surface activity, including sunspots, waxes and wanes over an 11 year cycle. 2008-09 was a solar minimum where sunspots eerily disappeared for awhile, and brought the quietest minimum in over a century. 2014 was supposed to be the latest maximum, but NASA dubbed it a “mini-max,” one of the weakest maximums in over two centuries. And since we’re even past the peak of the maximum, things aren’t looking good for stuff to look at on the sun – as evidenced by the fact that there’s only one sunspot group on this entire side of the sun.
Regardless, I do plan to take a look at the sun around once a week. That’s because the solar day is between 25 and 36 days long, so you can sorta take your sweet time in terms of not looking at the sun every single day as the sunspots rotate around. The sun is quite different from the moon in that regard; the moon changes dramatically in terms of what you can see each month due to the phases causing shadows to appear in different places, giving different lighting effects to the surface features. The ONLY thing that changes on the sun – at least through a standard solar filter – are the sunspots.
There is a different type of solar filter, called a hydrogen alpha filter, that shows you different types of details than just sunspots. Ha filters will show granulation on the surface, prominences, and flares. However, for some reason, Ha filters for solar use only come from ONE source – Coronado Personal Solar Telescopes. They have a monopoly in this area, and their prices are adjusted to ridiculously high levels accordingly. A simple 40mm telescope – which is only good for observing the sun – sells for anywhere from $700 to $1200. What a ripoff!
Why is a solar day 25 to 36 days, you wonder? Well, it’s 25 at the equator and 36 at the poles. Yes, you read that right, it doesn’t rotate uniformly – because it’s a giant ball of gas, the different parts are rotating at different rates. And that’s one of the main causes for why the sun’s surface is as active as it is, because the sun is an incredibly powerful electromagnetic force. As different parts of the sun rotate at different speeds, the magnetic lines of force start getting warped, and wrap around, until they get stretched past the breaking point. And that’s when the fun stuff happens – flares, prominences, coronal mass ejections, and, of course, sunspots.
Hopefully this minimum won’t last too long and I’ll get to see some stuff happening. Is it too much to hope to see two different sunspot groups at the same time?
Next time: the Baader Moon & SkyGlow Filter.