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Camera Obscura

Perhaps it's a little weird for me to begin an article with a glimpse of 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 at 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 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 first 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 pinhole 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 a couple of mirrors. Check below in references for the tutorial made by PetaPixel*, an online publication covering the wonderful world of photography, or many other DIY videos from YouTube. There was also a camera obscura exhibit made by Robyn Stacey**, an Australian photographer and visual artist, that turned the 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 was made with the camera obscura principle for observing the Sun, its sunspots, planetary transits, and eclipses. Despite its size, it was surprisingly quick and easy to put together, or more likely, I am becoming much more experienced with paper gluing. :-) Surely, compared to the previously assembled Galilean telescope replica, it was easier to paste more non-round parts than before with the telescope's multiple tubes. Nevertheless, the Sun projector surprised me with its rather large size.

However, the kit is not an ordinary pinhole camera. Instead of a simple aperture of the 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. Best of all, it has a cardboard-made Dobsonian base and can be adjusted to any height between 0° and 90°. Furthermore, on both sides, there are quarter circles with degree scales, which determine the angle between the position of the sun and the horizon, which helps in 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 were glued perfectly and aligned for the light to be beaming 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 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 is 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 as 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 stayed for a while in the field of view along with small Mercury and a couple of sunspots.


Details from the Sun Projector's "First Light"

Amazingly, Camera Obscura could be dating even back to the past, all the 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 have inspired them to start with cave paintings. It was not away from logic that they would intentionally make 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. Nature is definitely full of wonders, even with something so simple to test, build, and understand, like it is with monitoring light behavior within a camera obscura. By using the same principle, it is possible to make a small projector that uses a light from a 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)
https://www.mpj.one/2023/07/galilean-telescope.html

What Do Jupiter and Mercury Have in Common?
https://www.mpj.one/2019/11/what-jupiter-and-mercury-have-in-common.html

Transit of Mercury
https://www.youtube.com/watch?v=e2yuXbUdj6o

Shoebox Projector
https://www.youtube.com/watch?v=WAsvUbysEk8

Ref:
 

Galilean Telescope

The knowledge and manufacture of lenses were known since the time of the old Greeks (the word "optics" came from the Greek word ὀπτικά, which means "appearance") and later in the old ages with Egyptian scholar Alhazen, who made important contributions to the study of optics in general. In Europe, the lenses arrived around the 13th century and immediately triggered the invention of the first eyeglasses. However, one important discovery had to wait three centuries later in order to set off a wave of new discoveries in the field of astronomy. The invention was made by Hans Lippershey, the spectacle maker from the Dutch city of Middelburg in the Netherlands, who in October 1608 tried to apply for a patent for a tool he described as an aid capable of "seeing faraway things as though nearby". It consisted of convex and concave lenses in a tube capable of magnifying objects three or four times. For strange reasons, the patent was rejected, but the new instrument immediately attracted attention. Now known as a spyglass, the invention ushered in a new era in astronomy and was the foundation of today's refracting telescopes.


Cardboard replica of the original telescope made by Galileo

Only half a year later, in the early summer, Galileo Galilei at the University of Padua near Venice started to build his first telescope based on the one Hans' made. He managed to design and build telescopes with increasingly higher magnifying power for his own use as well as for presents to his patrons. Galileo was a skilled instrument maker, and his telescopes were known for their high quality. Just like the initial spyglass from the Netherlands, his first telescope was basically a tube containing two lenses, but he managed to enhance the power that magnified objects approximately nine times with his first designs.

Even though Galileo perfected the manufacturing of lenses and telescopes—in later years he managed to produce over a hundred telescopes, some of them with magnifications as high as 33—only two have survived and can be seen in the Museum Galileo (Museo di Storia della Scienza) in Florence. One of the two, especially designed for Cosimo II de' Medici, Grand Duke of Tuscany, with gold-embossed leather, probably had (with initial lenses from the end of 1609) magnification power of around 20. The limiting factor of these early refractors, especially those with higher magnification, was their small field of view, but still, it allowed Galileo to see that the Milky Way is just a multitude of millions of stars and that the Moon's surface was not smooth and perfect but rough, with mountains and craters whose shadows changed with the position of the Sun. He saw the phases of Venus throughout the year and the most interesting fact that planet Jupiter was accompanied by four tiny satellites that moved around it with distinctive proof that not everything in the heavens revolves around the Earth.


Phases in assembling Galileo's historical telescope

This particular gold-embossed leather telescope from the Florence museum was the model for the AstroMedia cardboard replica kit I got my hands on last weekend. It was advertised as "With this historically accurate cardboard replica, you can experience firsthand the great research achievements of Galileo, which he achieved despite the optical performance of this telescope, which is modest by today's standards". All I could say after two days of carefully pasting pieces of paper one after the other was that I couldn't agree more, especially at the last moment when I pointed it to the one-kilometer-away sign of the neighboring shopping center and clearly read what it said. I can only imagine where Galileo pointed his first telescope and what his initial reaction was.

While Galileo did not invent the telescope in the first place, his contribution toward their use in astronomy and science earned him two phrase coins: Galilean telescopes, which now represent a popular name for a refraction telescope type, and Galilean moons, now referring to the first four of Jupiter's natural satellites.


Jupiter's moons as seen through modest reflecting telescope compared to the view
from a small refracting spyglass similar in size to Galileo's original telescope

Unfortunately, I cannot make any astronomy photos with this replica; after all, it is made of cardboard, and fixing it on the moving sky is a mission impossible, not to mention its extremely small field of view, which is perhaps less than a centimeter in apparent terms, which would provide only troubles for focusing the camera through it. For these reasons, I decided to embed a photo of Jupiter's moons as seen with a modest reflecting telescope (the one you can see in the background of the first image above). Below you can find a link to the YouTube video of the entire event we created a couple of years ago when Jupiter was close to Earth. In the upper right corner of the photo, I also included a small view of how Galileo might have seen Jupiter and its four large moons. It is what can be seen with a decent refracting spyglass or powerful binoculars, which, in terms of magnification power, stand at the level of Galileo's scopes.

Camera Obscura (AstroMedia cardboard kit #2)
https://www.mpj.one/2023/07/camera-obscura.html

Jupiter Moons (zviktor22):
https://youtu.be/VTEsXEx-tnE

Ref:
https://astromedia.de/Das-Historische-Galileo-Teleskop
https://catalogue.museogalileo.it/index.html