Skip to main content

Camera Obscura

Perhaps, it's a little weird for me to begin an article with a glimpse to a romantic movie, but I can't think of a cooler way to start today's topic. When I came up with the idea to write about "Camera Obscura", the first thought that came to my mind was a movie from 1997, called "Addicted to Love". Of all the movies in this genre only a few are on the top of my mind and this one, directed by Griffin Dunne with Matthew Broderick and Meg Ryan in lead roles is definitely the best one I remember. In short, Sam, an astronomer who, in an attempt to win back his girlfriend, turns his astronomical tools into specific spy equipment and by using his dark-chambered pinhole camera manages to observe what is happening in the building across the street in the real time. What he used to achieve this is a principle behind Camera Obscura - a method to project the light through a small hole and create an image on the opposite wall inside a dark room, tent, or box. Something firstly observed and described by Mozi, a Chinese philosopher, around 400 years before Christ.

AstroMedia 'The Sun projector' cardboard kit

To better understand what Camera Obscura really is, think of an eye – a small, almost spherical chamber where light enters via the cornea and through a small pupil with the iris controlling how much light enters the eye. Light then passes through a lens which can change its shape to focus the image. The image is projected through a transparent, gel-like substance to the back of the eye (retina and macula), which contains light-sensitive cells. The light travels in straight lines from its source and because of this the image is formed flipped and upside down. However, the brain receives the image via the optic nerve and interprets the scene correctly.

Just like in the movie and inside the eye, we could also create our own Camera Obscura, which in Latin means "Dark Chamber". Imagine a large room completely darkened by for example placing cardboard sheets over the windows with a small shaped pin hole in the middle of the cardboard. The light from the outside will enter and paint a great image on the opposite wall of the objects from the exterior. Upside down and flipped but that could be fixed by utilizing couple of mirrors. Check below in refs the tutorial made by PetaPixel*, an online publication covering the wonderful world of photography or many other DIY videos from the YouTube. There was also a camera obscura exhibit made by Robyn Stacey**, an Australian photographer and visual artist, that turned Australian city of Brisbane on its head in stunning photographs.

Convert your room into a giant Camera Obscura by PetaPixel*

Today, as a continuation of the small astronomy thread on MPJ, I had my hands on a second AstroMedia kit (of three) and this one made with Camera Obscura principle for observing the Sun, its sunspots, planetary transits and eclipses. Despite its size, it was surprisingly quick and easy to put it together, or more likely I am becoming much more experienced with paper gluing. :-) Surely, compared to previously assembled Galilean telescope replica, it was easier to paste more non-round parts than before with telescope's multiple tubes. Nevertheless, the Sun projector surprised me with its rather large size.

However, the kit is not ordinary pinhole camera. Instead of a simple aperture of Camera Obscura, the solar projector has a lens and two convex mirrors to choose from that work together like a Galilean telescope from the previous post. It is designed to provide higher magnification, and a plane mirror redirects the image to a comfortable viewing position. The best of all it has a carboard made Dobsonian base and can be adjusted to any height between 0° and 90°. Furthermore, on both sides, there are quarter circles with a degree scales which determines the angle between the position of the Sun and the horizon, which helps calculating the height of the Sun. With additional apertures it is possible to reduce the opening and amount of light that enters the box. Smaller apertures can make sharper images. It's a surprisingly comprehensive astronomical tool.

Phases in assembling the Sun projector

To be honest, I was a bit skeptical that all the parts was glued perfectly and aligned for the light to be beamed exactly from the objective lens through the convex mirror to the plane mirror and toward the white screen but the "First Light", as the astronomers like to call the time of the first observation with a brand new equipment, showed the Sun disc amazingly clear and focused. Now I have to wait for the next eclipse to test it with, which will be in March, 2025. Or for the next Mercury transit nine years from now. Unfortunately, the transit of Venus will not happen again in this century. In the meantime I will definitely play a little more with it and test all its features, including observation of landscapes as in the summer there are plenty of light so stay tuned for more information about all it can do.

Unrelated to this project, it reminded me that observing the Sun could be very interesting and enjoyable. Once, when I was watching the Sun through the reflecting telescope with a solar filter, a plane transited the Sun disk at the same moment of my observation of one of the previous Mercury transits and it was so intense, to say the least. Imagine watching Mercury slowly pass through the sun's disk when suddenly the black shadow of an airplane passes the disk in less than a second. I was stunned for a moment trying to comprehend what exactly happened. I would probably still be puzzled by the event if the airplane hadn't left a contrail behind it which staid for a while in the field of view along with small Mercury and couple of sunspots.

Details from the Sun Projector's "First Light"

Amazingly, but Camera Obscura, could be dating even back to the past, way to the prehistoric settlements. There are theories that prehistoric tribe people witnessed the effect through tiny holes in their tents or in screens of animal hide which might inspired them to start with cave paintings. It was not away from logic that they would intentionally made the pinholes in order to monitor the exterior for potential dangers from within their shelters.

Anyhow, it was fun building the kit as well as writing about it. The nature is definitely full of wonders even with something so simple to test, build and understand like it is with monitoring light behavior within Camera Obscura. By using the same principle it is possible to made a small projector that uses a light from smartphone to project it on the wall and even the additional mirror is not required if the smartphone is positioned upside down in the first place. We played once with that as well and the result is in the refs below.

Galilean Telescope (AstroMedia cardboard kit #1)

What Jupiter and Mercury Have in Common?

Transit of Mercury

Shoebox Projector


© 2023 Milan's Public Journal