Solar activity on January 19, 2023 ‐ Using the pinhole camera principle for a very simple and safe observation technique

The cycle 25 is now offering big sunspots, visible through a pinhole!

Solar observation and photography are requiring a safe equipment, as the sun power can induce irreversible eye damages in the case of an unapproriate setup. A very low-cost and extremely simple method is presented here: The pinhole camera. The magnification of the object, i.e. the sun, is given by the focal length of the setup, corresponding to the distance between the pinhole and the projection screen, e.g. the wall. The pinhole photographs have nearly infinite depth of field, everything appears in focus. However, the resolution remains very limited and only allow the observation of relatively big sunspots.

Source of the illustration: The Free Encyclopedia Wikipedia

 · Solar images taken with this simple setup

Setup: No need of optics, no need of any high-end camera. The blinds of the office in Marin (Switzerland) are acting as multiple pinholes. At a distance of about 6 meters, each pinhole is generating an image of the solar disc of the order of 6 centimeters. Some disc images display the shadow of a tree's branches in front of the window. As a reminder, this technique is offering a nearly infinite depth of field. Images have been taken of January 19, 2023 by a standard smartphone Samsung Galaxy S10. On the last image offering higher contrast, but also taken with the same smartphone, the limb darkening is detectable. Using a white and matte surface is recommended for getting a nice image of the sun. A white board is too glossy and the wall directly has too much rough structure. This is really a minimal and safe solar observation method… but with limited resolution of course!

© Michel Willemin

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