Solar Pinhole Observations - Philipp Salzgeber photography

Most people don’ t realize that the bright spots below a tree in the grass are actually images of the sun formed by small holes created through overlapping leaves in the tree’s branches. Because the sun is a sphere, the images are also circular (depending of the angle of the surface).

A similar situation occurs when the sun shines through the small holes in blinds – round images of the sun are projected against the foor or wall. The images become interesting when the sun’s disk is obscured by something, e.g. the moon during a solar eclipse or trees when the sun is rising or setting on a wooded horizon.

Here are some images I took in 1999 when we were living in an apartment that would have optimal conditions for observing such sunrises:

The floor plan allowed the sun’s images to be projected onto the kitchen furniture

A tree is silhouetted against the sun’s disc

When the sun was higher up I thought I was seeing some dark spots in the sun’s image.

Only when I increased the contrast of the image strongly three dark spots appeared.

I took this improvised image of the sun with a solar filter and a binocular and was able to prove that the sunspots in the pinhole image were not imagined

Here is a link to the sunspot drawing from the Kanzelhöhe observatory from this day: sunspot drawing 22.12.1999

During the 2015 solar eclipse I used two pieces of cardboard to project the sun through two holes, one 5mm in diameter, one 2mm. The bigger hole makes a brighter image, but the image from the smaller hole is much sharper:

Using pinhole projection, the eclipsed sun was easily visible

This is actually a safe way to observe a solar eclipse!