Solar Filter

I ordered two new lenses for my camera with the hope of catching some great photos of the upcoming Solar Eclipse. But of course, you need more than just good lenses – you also need a Solar Filter. Unfortunately, such filters can be enormously expensive, costing even more than the lenses themselves. (At least, more than the lenses I bought.) And since I want to be able to take photos with TWO different sized lenses, I would have had to spend quite a bit of money to protect my camera (and eyes) with both. So instead of buying a solar filter or two, I made my own.

Equipment:

I haven’t actually used the wireless remote yet, other than to test it out (and ensure it will wake the camera up from sleep if I set a time-lapse timer). I’m hoping to do a test run before the eclipse, and figure out exactly how to position the camera so that I can capture the whole event (1:17-4:13pm) without having to move the camera or tripod. Problem is, it has to be sunny to test that, and it’s been raining nearly every day so far this month. So we’ll see.

Now, on to making a solar filter. Note that “High Density” filters and “UV Filters” are NOT sufficient for photographing the sun. You need an actual solar lens that allows only “1/1000th of 1%” of light to penetrate. Check out NASA’s list of reputable vendors, and scroll to the section titled “Solar Filters for Telescopes, Binoculars & Camera Lenses” if you want to use something other than what I used myself.

Supplies:

  • Solar Filter Sheet (this is on NASA’s list of reputable items) – get a size that comfortably covers the diameter of the largest lens you want to use. A 6×6-inch sheet easily covers a 95mm lens. (This is the diameter of the 650-1300mm focal length lens I bought.) Note that the price is skyrocketing as we approach the eclipse. I bought mine a week ago for $17. As of last night the price was $30, and it’s now up to almost $60. So this may no longer be a more economical solution that just buying an actual solar filter, if you can find a reputable one of appropriate size.
  • Cardboard from a “fridge pack” beverage case
  • Cardboard from a beverage six-pack
  • Clear packing tape
  • Scotch Tape
  • Scissors
  • Pencil
  • Ruler
  • Knife

Note that there are other methods to attach the solar filter sheet to your lens. You can wrap it on the end of your lens and hold it in place with a rubber band, but I didn’t want to do this for two reasons. One, it wrinkles the sheet, and may cause damage. Two, that’s more of a pain in the butt to put on and take off, if necessary. Other people put the sheet between squares of acrylic, and/or use a PVC pipe that fits over the end of the lens. The problem with both of these methods is the added weight. The lenses themselves are already quite heavy, especially the Opteka, so I wanted my solution to be as lightweight as possible. Using the thin cardboard that makes up soda cases & six packs helps keep the weight as low as possible.

Method:

  1. Cut a strip of the beverage fridge-pack case along the longest side. Make sure you use a strip that doesn’t have any perforations or tears. I used a width (circumference) of one soda can as the width of the strip, in order to ensure a secure fit over the lens body. This also makes it pretty easy to cut, because there’s usually an indentation of the bottom of the cans in the cardboard, so you can see where your center line would be.
  2. Wrap this cardboard strip around the widest part of the end of your lens. Make sure you’re still able to adjust the focusing ring, whether or not your cardboard will cover it. Also make sure that when you adjust your lens to be its greatest length, it won’t push your filter off the end of the lens. You want the ring of cardboard to be tight enough that it will stay snug on the end of the lens, but loose enough that you can easily put the ring on and take it off.
  3. Tape the ring closed with clear packing tape. Use tape on the outside, and then more tape on the inside, so that the inside flap doesn’t catch on anything.
  4. Cut out the two large faces from the six-pack. You will have to tear off the inner dividers that are glued to the inside walls. If you want the picture on the outside of your filter, I highly recommend using a very fine nail-file block to smooth out the spots where the dividers were attached. Rough spots may damage the solar paper. If you have the image/outside of the cardboard facing in towards the solar paper, this is less of an issue.
  5. Measure a square that is the same size as (or very slightly larger than) the solar paper that you’re using. I have 6×6-inch solar paper, so I measured out 6-6-inch squares on the cardboard. Carefully cut out this square on each of the two panels from the six-pack.
  6. Place the large-end of your lens on the center of one of the squares, and use a pencil to trace around the lens. This is the minimum size for the hole you’re going to cut, as you don’t want any of the cardboard poking in from the edges of the lens. The maximum size of the hole will be the circular-cuff you made to go over the end of the lens. The difference between the minimum and maximum size is a couple of millimeters, but anywhere in that range is fine.
  7. Use a knife to poke a hole in the center of the circle you just traced. Use scissors to cut a spiral pattern into the center of the cardboard, widening slowly each time you go around. You don’t want to just cut straight out from the center towards your pencil line, and try to turn the scissors at the last minute. A spiral cutting pattern ensures you get a smooth curve as you start cutting along your line.
  8. Line up this cardboard piece with the other piece from the six-pack. Make sure the sides are facing the way you’ll want them to face on your final project. Use a pencil to trace the circle from the first panel into the second panel, and then use the spiral-cutting method to cut the circle out of the second panel.
  9. Lay the two panels end to end along whatever edge you want to be the “spine” (or permanently closed edge), and use clear packing tape to tape them together. Make sure the packing tape is on what will be the “outside” of your filter.
  10. Add clear packing tape to all of the edges all the way around both sides of the filter, being careful not to let any tape cover any of the hole. Cut along the outside edge to remove excess if necessary. Adding this packing tape does two things: it makes your filter slightly more moisture resistant, and more importantly, it provides a semi-sticky/semi-slick surface for the scotch tape later.
  11. Put the cuff you made out of the fridge-pack case on top of the outside of one of the panels, lining it up with the hole. Using strips of clear packing tape (no wider than a half inch each), begin taping the cuff to the panel. I start with the four “cardinal directions”, and then add tape on the diagonals, and then go all the way around again to make sure there are no openings. Keeping the tape to a half inch or thinner helps prevent the sides from separating, due to the curve of the cuff.
  12. “Close” the two panels so that the insides of each panel are facing each other. Get a piece of Scotch Tape about 1-1.5 inches long. Fold one end over at about a quarter inch, to make a “flap”. Attach the other end to the “back” of the panel (the side with the cuff is the back), towards the edge, and fold the Scotch Tape forward so there’s a bit of tape on the front before the flap. I was able to fit 2-3 of these flaps comfortably on a 6×6 panel. (See images above and below if this isn’t clear.)
  13. Pull all of the Scotch Tape flaps back so you can open the front panel back up. Insert your solar sheet, SILVER SIDE OUT (silver towards sun). Close the front panel and secure the Scotch Tape over the front again.
  14. Slip the cuff over the end of your lens, and voila!

I realise these don’t look as finished and professional as an actual solar filter, but it saved me from spending $200-300 each for the “real thing”. There are inexpensive alternatives (DayStar Universal Filters), but they’re back-ordered until who knows when. I may consider purchasing the two appropriate sizes sometime down the road, but the solution I came up with will work for now!

The above photo was taken with my 75-300mm lens and the home-made solar filter. It may not be super impressive now, but the small size of the sun in the image is actually an advantage over the larger lens. If I use the 650-1300mm lens, the sun would take up much more of the frame. This means it would move across the whole field of view before the end of the eclipse, which would mean I’d have to keep moving the camera and tracking the sun. Using the 75-300mm lens (which I’m calling my “medium” lens”) means there’s a much wider field of view. I am hoping this is wide enough to track the sun for the entire duration of the eclipse (3 hours at my latitude), without having to move the camera. I’m not SURE that it will all fit, which is why I need to test it out. If the sun stays out long enough today, and it doesn’t rain or get cloudy, I will try to do this today. This will also help me figure out the track that the sun is going to take, so I can position my camera in a way that the sun’s path is on the long axis of the image.

I haven’t been able to get a photo of the sun with the 650-1300mm lens yet. It’s really difficult to find something that appears so small in the sky with such a narrow field of view, especially because I can’t look through the optical viewfinder (or directly at the sun) to find it. I have some solar glasses on the way, and once they arrive I’m hoping they’ll make it easier to get the sun centered in the lens. I did take some practice photos of the moon though, and I’m super happy with how they came out. They won’t make the cover of National Geographic, but they’re far better than any moon photos I’ve taken before. Interestingly, 1300mm is TOO MUCH for moon photos, as the moon is so large in the frame that it doesn’t even fit in one image. So the below was taken at 650mm.

Another problem with the 650-1300mm lens is the weight. Even using a heavy-duty tripod, it’s impossible to point the lens in the direction I want and lock it down tight enough that it doesn’t move. The only solution I could come up with was to use a second tripod (larger tripod under the lens, smaller tripod under the camera), and even this wasn’t a perfect solution. It looks like if I want to get a really steady shot, I’ll need to set up a table and some kind of ramp to elevate the lens to the needed height. But even still, I think the photo above is really nifty! Especially considering I’m using a ~$400 camera and lenses in the $100-200 range, which are totally on the bargain-end of the spectrum. You can easily spend thousands of dollars on cameras and lenses that would definitely get better photos, but as an amateur photographer I can’t justify that kind of cost. I’ll save the bigger-ticket purchases for when I win the lotto. ;]

I’m looking forward to learning more about how to use my camera and the new lenses, and I hope to get some really awesome photos (including some of the sun with the solar filter)! So exciting!

For tips on how to actually film the eclipse, and what to look for, I’ll leave that to SmarterEveryDay!

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