Photographing the Sun

With the very rare 2024 total solar eclipse coming up, I have gotten interested in solar photography. This article describes my DYI "Sun finder". There are plenty of "sun finder" products on the market, but everybody was out of stock, presumably because of the upcoming eclipse. The article also provides some general information about solar photography. You can click on any image in this article to see it in higher resolution.

The gear I'm using is:

• Pentax K3 DSLR (1.6x crop sensor)
• 55-300mm zoom + 1.4x teleconverter
• 35mm equivalent telephoto: 300 * 1.4 * 1.6 = 672mm.
• Resulting diameter of sun image: about 945 pixels
• ABSOLUTELY REQUIRED FILTER: 16.5 stop neutral density, often referred to as "ND100000" because 2 to the power of 16.5 is about 100 thousand.
  DO NOT LOOK AT THE SUN THROUGH THAT FILTER -- CAMERA ONLY!!!
  

I used "live view" so I could avoid looking through the viewfinder. An alternative would be to get some certified mylar solar filter material and put that over the front of the lens lens instead of the ND100000 filter. Mylar solar filters (the stuff used in eclipse glasses) allow you to look directly at the sun. The filter must be between the camera and the sun, not between the camera and your eye.

To see how well the photos came out, I went to https://spaceweather.com/, where they have high-quality images of the sun showing the sunspots that are present. The images are updated every day. Here's what they showed on the day I did these test shots:

With my particular filter I found that a 1/320 shutter speed and ISO 100 with apertures between about f/8 and f/13 worked well. The first shot above was at f/13 and the one below was at f/8. Focusing can be a bit tricky, and you're not going to get a tack-sharp image unless the atmospheric conditions are super-clear (a cold day in a desert, maybe). Notice that the image below is a bit softer than the first one in this article.

You also have to aim the camera at the sun, obviously, and the longer your lens the more difficult that is. You want the sun fairly well centered in the frame, as shown below. Bear in mind that the angular diameter of the sun is about 0.53 degrees, so you really don't have to be out my much in your aim for the sun to be completely outside the frame. That's where the "sun finder" comes in.

The astute among you might notice that I had anti-shake turned on. I should turn that off, and also make sure the clock is set correctly.

I did some shots just by looking at the shadows on the lens barrel. When the circular shadow of the lens hood on the camera body is centered with the base of the lens, you're probably pretty close. For a less-than-once-in-a-lifetime event (the next solar eclipse here will be annular, not total, in 2093), I want to do better than "probably pretty close".

Here's an example of a commercially-available "sun finder" for telescopes (and hey, it's back in stock!):

I wanted something that can mount to the hot shoe on my camera, not on a telescope. I wanted it to be nice and solid, so it won't shift around. You can get a telescope "dovetail" mount and adapt it to the hot shoe, and use a sun finder similar to the one above. Or you can channel your inner Rube Goldberg, using whatever you have handy.

What I have handy are a lot of Smallrig camera-rig parts (smallrig.com). The ludicrously-complicated contraption you see below consists of:

• two 15mm rails, 20cm long
• three "railblock rod clamps", which clamp to the rails and have lots of threaded holes
• a hot shoe adapter with a 1/4"-20 screw
• two "cheese plates", littered with threaded holes
• one lense support, which clamps to the rails and rests against the lens, the idea being to stabilize the rig against the lens, with the support mounted upside-down

It's not crazy if it works. So does it work?...

By the way you can just make out at the bottom of that photo that I have two tripod heads. The big ball head on the (also big) tripod is tilted about 47 degrees off-vertical, because my latitude is about 43 degrees. With the tripod aligned with true north, that makes the plate on the ball joint "equatorial", meaning that it is parallel to the plane formed by the earth's equator.

On top of that is a geared tripod head. A pan head would also work, but the gear head gives me really fine control. The gear head is what I mostly use for studio photography.

Screwed to the front cheese plate is a heavy card with a pinhole in it. That's how the sunlight gets in. You're not really trying to make a clear image of the sun with this thing. You're just trying to make a dot on the card at the back.

A business card is taped to the back cheese plate. Using live view on the camera, I aimed the camera so the sun was in the middle, and so that it was just about touching each edge of the frame, and made marks on the card with a narrow-point Sharpie. Now I can very quickly aim at the sun by looking at the card and getting the bright spot onto the center mark. Easy.

Here's a view that maybe gives a better idea of how the parts go together. You can't see the shoe adapter but it's pretty obvious where that goes, and all the other parts are visible.

The contraption I built is far more elaborate than it needed to be, but it went together very easily using parts I happened to have lying around. I suspect you could make the entire thing out of cardboard (except maybe the hot shoe adapter) and get acceptable results. Happy shooting!