Shooting the Sun

I've been playing with astrophotography this year; mostly shooting images of the moon through the telescope. Today, I tried my hand at the sun. I have been planning a solar observer for some time, so today I built a small prototype. It's not unlike a pinhole box we used in school, but this time, I decided to incorporate a scope. For the prototype, I used a consumer-grade set of binoculars from Bushnell. Here is the setup:

I used a 37" long cardboard box. The interior is the traditional brown (no black paint to minimize light reflection). I cut a hole in the side for the camera, which viewed from the top. The camera was my Nexus 5x smartphone. I ended up zooming in 4x to get the image as large as possible in the frame. For the reflective surface, I used a piece of Kodak matte finish photo paper mounted onto a piece of copier paper, in turn mounted on a piece of cardboard. Here's what I ended up with:

You can see four sunspots in the upper-left quadrant of the frame. Unfortunately, they looked better when looking directly at the image, but this is just the first attempt. There was some post-processing to get the image you see here:

• Removed dark spots caused by debris landing on the paper during the shoot.
• Increased contrast, and reduced brightness slightly.
• Added details about the shoot to the image.

The achromatic aberration was much more dramatic than I expected. While undesirable, it makes for a good discussion on how light bends through glass.