Enthusiasm preserves thousands of historical images of sunspots

Nearly 40 years ago, the University of Oslo (UiO) closed its research activities at the Solar Observatory in Harristoa. Over the course of just over 30 years, from 1954 to 1986, several thousand images of sunspots were taken at the Sol Observatory. The images were invaluable because they were able to study variation in solar activity. 15 years ago, the site was separated from UiO. Today it is a visitor and information center for school classes.

Modern in the fifties

When Seoul Observatory opened 70 years ago, it was considered very modern. It has attracted solar researchers from all over the world.

The observatory was full of modern equipment. The main attraction was the largest solar telescope of the time in a 20 meter high tower. It was used to photograph sunspots. The observatory also obtained a spectrometer to measure the speed of solar storms and a radio telescope that was used to study the dynamics of sunspots.

Combining observations from these three instruments has enabled astrophysicists to document solar storms that no one else has been able to document, says today's head of the solar observatory, Vegard Lundby Ricca.

Old style 80's

By the 1980s, their equipment was outdated.

-If the telescope was still usable, major improvements had to be made. The university was not prepared to make this investment. Instead, the university joined a joint venture to operate the Swedish Solar Telescope in La Palma, northwest of the Canary Islands.

It was actually a good idea. Solar researchers naturally rely on good weather. Norwegian weather isn't exactly anything to brag about. Observation conditions are much better on the Spanish island than on Harristoa.

– During the operation of the solar observatory, sunspots were systematically observed. Whenever possible, preferably several times a week, astrophysicists take the same type of images of the Sun's surface, Ricca says.

In total, several thousand photos were taken.

Forgotten in boxes

When the observatory was closed, the images were forgotten. Some of the images ended up in the basement of the Institute of Astrophysics at UiO. Others remained forgotten in dusty boxes in the eventually very dilapidated buildings of Solobservatoriet, located deep in the forest at Gunnarshøgda, 580 meters above sea level, a half-mile drive up a bumpy forest road from Harestua station in Löner municipality.

Thanks to a couple of fanatics and a good dose of luck, the historic original glass plate negatives have now been preserved from the elements. Now the photos must be preserved for future generations. Where has not been decided yet. A possible solution may lie in the climate-controlled archives of the National Library inside the mountain at Mo i Rana.

Consolidated registrations

All photos are taken with good old fashioned photography techniques. Here we are talking about negative glass plates of 10 x 13 and 12 x 16 cm.

It wasn't enough to take pictures of sunspots. All photos were to be taken in the same way. Astrophysicists were then able to figure out where different spots on the Sun were located at any given time.

– In other words, we have a unique historical archive from the 1950s to the 1980s that researchers can use to study sunspots over a 30-year period.

magnetic field

Astrophysicists at the Solar Observatory also took a number of pictures of the magnetic fields on the sun.

Sunspots always come in pairs. While one sunspot has a positive magnetic pole, the other has a negative magnetic pole.

Thus there is a relationship between magnetism and sunspots.

One of their tasks was to find out where sunspots appeared on the solar disk, where they migrated from and where they disappeared, says Ricca.

These images were important in proving that the sun's magnetic field changes between the north and south poles every eleven years. Astrophysicists were also able to prove that the number of sunspots is often larger at a pole shift.

International Desire

A few years ago, the International Astronomical Union (IAU) urged astrophysicists to take steps to preserve the archive in older analog formats.

-One day questions will arise as researchers want to look at historical data.

Although Ricca has not yet reached the International Astronomical Union, he still hopes that their archive will have meaning at the international level.

-Are there similar archives elsewhere?

-We don't know that. The important point is that weather varies from place to place. It is not always possible to take pictures of the sun. Moreover, this cannot be done without human and technical errors. Maybe we find photos in our collection that are not good enough. We can then supplement them with images from other archives.

Cleaning in the basement

Many of the images ended up in cardboard boxes in the basement of the Institute of Astrophysics. When the institute was scheduled to be renovated a few years ago, the basement had to be emptied. The boxes were transported to the Seoul Observatory.

When Rika compared the contents to what was scattered in the boxes at the Sol Observatory, he understood the scope.

By sorting through the contents of all the boxes, he found weekly images of the sun's surface from 1954 to 1986.

Photo saver

Three years ago, Ricca brought with him Spanish photographer Pablo Castilla, who happened to be his neighbor in Harristoa. Castilla is an artist, portfolio artist, and expert in wet plate photography.

– Castilla says: – I wanted to make an effort to preserve the photos for future generations.

Apply for support to save the Norwegian scientific contribution to heliophysics. He received 190 thousand Norwegian kroner. The cost of the work is NOK 300,000. He took the rest on his own mantle.

Now he cleaned all the glass panels. He also gave each of them an identification number.

– He points out that without organized collection, information is not worth anything.

In all, he saved 3,193 objects. Of this, 2,473 are glass negative plates.

Castilla hopes that he will soon be able to begin the painstaking work of digitizing the collection and ensuring that it is sent to a suitable repository for future generations.

– What would have happened if you had not addressed this matter?

“If we don’t store these things properly, the objects will be destroyed,” says Castilla, who described in his final exam at the Autonomous University of Barcelona in Spain how the collection at the Solo Observatory could be preserved.

Historical value

One of the many people who have photographed sunspots is Torben Levsen from the Institute of Astrophysics. He worked as a research assistant at Solobservatory for the last few years before it closed.

– Sunspot images were important as supporting material for other observations of the Sun. In modern solar research, images are of no value, but the material is important for those who want to study what the Sun looked like in the past. The material is therefore of historical importance. Moreover, we don't know what will be important in the future. It is therefore important not to waste the material, Levson points out.

He is happy to take care of the photo plates from the Seoul Observatory.

– It is now archived in a way suitable for future generations. it is good.

Professor Mats Karlsson, the university's leading solar researcher and head of the Roseland Center for Heliophysics, a center for research excellence, believes that preserving the collection could be valuable to science.

– It is not usual to use the same tool for a long time. The observations were made using almost the same equipment, and over a period much longer than 11 years, the length of the solar cycle. This set will always have value, but I don't know anyone who plans to use it. He points out that there are likely some people in the world who conduct long-term studies of solar activity and know nothing about this substance.

The article was first published in Apollo