Stefan Kürti´s Astro Web

Operator of robotic telescope in South America

A rare celestial event raised his interest in the starry sky, though he did not even observe it. As a passionate stargazer he dit hesitate to travel hundreds of miles to observe it under the dark sky. He discovered the beauty of variable stars in Eastern Slovakia and began to observe them from the balcony of his apartment. He thanks his job to a bright comet, and nowadays he gets valuable data for physicists from the comfort of his home. Operator of robotic telescope, Martin Mašek.

Many different ways lead to astronomy: one follows a friend, somebody is attracted by a simple look through the telescope, while someone else is fascinated by falling stars. What got you into astronomy?

It was a total solar eclipse which was visible from Central Europe in 1999. I was 11 years old. Although the totality hadn´t reach Czech Republic, the Sun was covered over 90%. It was fairly mediated in newspapers and television, so I had liked to watch it. I bought special solar eclipse glasses from Prague Observatory. Due to the bad weather I could not seen anything from Liberec. But the interest in astronomy remained and afterwards I received the CD “Encyclopedia of the Universe” as Christmas present. Then I started to visit a library and borrowed astronomical books and my familiarization with the sky began. From the beginning I observed visually, I made drawings of planets, deep-sky objects, comets in observation diaries. I still keep them up. Later, I tried to capture the beauty of the universe by camera, first through analog, later digital.

You graduated from the nical University of Liberec with a major in Applied Geography, but you are employed at the Institute of Physics of the Czech Academy of Sciences. Comet C/2011 W3 (Lovejoy) and the FRAM robotic telescope was your admission ticket to this job. How did it happen?

Comet C/2011 W3 (Lovejoy) was practically visible only from the southern sky. My friend and active comet observer Jakub Cerny asked the then-colleagues from the Physical Institute whether they would capture the comet using their robotic telscope FRAM in Argentina. As the weather allowed, the comet was observed for several nights before its closest approach of Sun, following it even afterwards. Thanks to this, the unique data of this Kreutz family comet was acquired. I participated in processing the astrometry, which helped determine better orbital elements of the comet. The FRAM telescope also got its observatory code I47. It has turned out that the day-to-day supervision of FRAM is appropriate; unexpected alerts require rapid response and data processing. Thanks to Lovejoy comet, I became part of a team of people around FRAM.

I am concerned about running two robotic telescopes, their acronym FRAM stands for the Photometric Robotic Atmospheric Monitor. The first FRAM is located at Pierre Auger Astroparticle Observatory in Argentina, and its main task is to monitor the state of the Earth's atmosphere above the observatory. The telescope studies light scattering depending on the wavelength. It also analyzes the state of the atmosphere along the trajectory of remarkable or anomalous cosmic rays. The second FRAM was built in 2017 and is based in Chile under Paranal. It will serve the Cherenkov Telescope Array astro-particle research project, which is currently under construction.

As it is not necessary to monitor the state of the atmosphere through the whole night, the remaining time is used to observe interesting astronomical targets such as comets, near-Earth asteroids or variable stars. I prepare an observation plan in the evening; I specify objects to observe and produce an observing session which then runs automatically. In addition, I do regular monitoring of all systems – cameras, focusing, assembling, control software, etc. If something gets wrong for some reason, I need to intervene (e.g. restart). The next day, usually in the morning, I check whether the night has gone well, then I download the data and process them.

Do you work from home or do you travel daily to Prague?

Part of the job is at night, so I usually work from home. The time-zone shift between the Czech Republic and South America (Chile, Argentina) is about 5 hours, so I have a customized daily regime that is a little shifted. If the weather permits, FRAM usually observes 24/7, regardless of whether it's a weekend or a holiday.

How should we envision atmosphere monitoring through FRAM telescope?

Vertical sketches of the night sky are being executed, so images of star fields at different altitudes above the horizon are photographed in different photometric filters. These are then compared to the star catalog, which makes it possible to measure extinction. The knowledge of atmospheric extinction is essential for the astro-particle observatory, as cosmic rays pass through the Earth's atmosphere, and for the correct calibration it is necessary to know the current state of the atmosphere.

How much time does it take during one night?

Because of thin purpose of FRAM, there is more free time for other observations around the full moon, when the astro-particle observatory does not observe cosmic rays with fluorescence detectors. Then, roughly two-thirds of the night can be used to observe various astronomical targets. Around new Moon, the situation is the opposite; there is less observational time for astronomical objects. Additionally, it observes the trajectories of random cosmic rays. This has a high priority and if such a particle arrives from the universe, the telescope starts scanning its trajectory. If a comet or a variable star is observed at that time, the observation is interrupted and starts again once the scan is completed.

The FRAM telescope got its observatory code in December 2011. Afterwards you started to use it for astrometric observations of asteroids and comets. Just few months had passed and in May you recovered comet P/2005 K3 (McNaught) at its second return. The comet is now registered as 260P/McNaught. You searched for it purposefully. How did this idea arise?

The well-known Japanese astronomer Seiichi Yoshida has a web site aerith.net dedicated to comets which are waiting for recovery. I chose Comet P/2005 K3 from his list in the spring of 2012. It had good conditions for recovery on its second return to the Sun in the southern hemisphere. I made a couple of attempts, and after a month from the start I cauit on May 15, 2012. The comet was only a few arc minutes away from the predicted position.

Later you recovered other two periodic comets 296P/Garradd and 300P/Catalina in 2014. Do you search for such comets regularly?

Not regularly. There is not enough observation time for this, yet it is not the main observation task for FRAM. Anyway, I tried it a few times and succeded. In some other cases, I have failed; the big robotic surveys can look deeper and have a larger field of view than a small FRAM with a lens of 30-cm diameter.

You gained the skills of astrometry during your search for new asteroids in the SkyMorph/NEAT archive. Don´t you have a temptation to find a new asteroid through FRAM from the southern sky?

The vast majority of new asteroids is found presently by big robotic surveys. There is no room for systematic hunt with FRAM due to its main observation program. Anyway, I always check the images and try to get as much data from them as possible. A new asteroid has not been found yet, but some of the nice rewards are newly discovered variable stars, which are astrophysically interesting.

Thanks to working with the FRAM telescope, you traveled to Argentina. Do you remember your first view of the sky from the southern hemisphere?

I had the opportunity to travel to Argentina twice as part of regular telescope maintenance. A big problem there is the dust that is ubiqus in Pampas. Not only optics, but also other components of telescope suffer. The optics requires cleaning and collimation once in a while. And also assembly gears must be cleaned and lubricated regularly.

I remember well my first glance at the southern sky. It was cloudy upon arrival in Malargüe, the city where Pierre Auger Observatory has it’s headquarters. In the evening we went shopping and for the first time I saw the Southern Cross between the clouds in front of the department store. The following days the weather was better; moreover it was in Pampa, outside the city. Magellanic Clouds were visible at dusk, but the best came during astronomical night. The Milky Way in the Sagittarius was directly overhead, the Milky Way's structure looked like in black & white photographs. Really indescribable! Many people do not even know how amazing the starry sky could be in places without light pollution. It could not be compared with the light polluted sky in the Czech Republic.

The threat of light pollution grows. Besides astronomers also the politicians in the Czech Republic are aware of it. Is it possible to slow its progress or even reduce?

I have been dealing with light pollution for many years, I measure the brightness of the night sky in different places regurarly. I also try to popularize this issue on websites and social networks. I think light pollution will continue to rise; the public lighting is expanding and shines more & more strongly. Modern LED lights are more economical, so the outcome of it is other illuminated areas, which were not previously illuminated for economic reasons. The major drawback of most LEDs as well as sodium light lamps is that they light up in a wide band of visible spectrum and cannot be filtered. But there are, for example, PC Amber LEDs that light up in the narrowest part of the spectrum, without the blue light component. In this respect, the PC Amber LEDs for astronomy and the night environment are more suitable than white LEDs.

The Ministry of the Environment of the Czech Republic is aware of the problem of light pollution and has established an inter-departmental group dealing with this issue. They managed to issue a guide for municipalities, where it is described how to lighten, so that the streets are not only safe but also respectful to the night-time environment. Unfortunately,  is only on a voluntary basis at the good-will of municipalities and businesses, and certainly not everyone will follow it. Many businesses, towns and municipalities have poorly designed outdoor lighting simply because they do not know about the issue, or they want to save on expenses as much as possible. So the illumination looks like this, also often the lamps illuminate places that should not be illluminated. You need a designer who will adjust public lighting according to experts‘ advices. It should be used properly – only the places in needed and only as strongly as necessary – and should definitely not be stronger, should not use white LEDs but only LEDs with lower chromaticity temperature (e.g. the PC Amber mentioned above). To achieve this, it will require a law that will be enforceable. There is no other way to improve this situation.

There are three dark sky areas in the Czech Republic and four in Slovakia. Will there be another in the near future?

In the near future, the area of dark sky in the Podyjí National Park could be created. There is a fairly solid darkness in the Czech Republic. But unfortunately, there is no longer a natural dark sky in the densely populated Central Europe. It is a problem to find a place with a sky that still retains its natural darkness. The darkest places in the territory of the Czech Republic are at Bortle 3 level in the scale of light pollution. Even though these are relatively remote sites that are tens of kilometers away from the big cities, the influence of light from these distant large cities is still noticeable in the night sky. In other parts of the country, the situation is worse, depending on population density and distances from cities. This is what many people do not realize, and they mistakenly think that in order to see the dark night sky it is enough to go up the hill behind the city.

You are keen variable star observer since 2008. What was the reason you got involved with them?

Previously, I was mostly a visual observer of deep-sky objects, comets and planets. To observe dimmer objects you need a real dark sky. Unfortunately there is no longer such a place in the Czech Republic. My friend Laco Bálint recommended to visit Kolonica observatory, located in the east of Slovakia, where the sky is darker than in Czech Republic. There are various observation events held there during the course of the year, predominantly for secondary school students. The main observing program of this observatory is variable stars. During my visit, besides vi observation of meteors and deep-sky objects, I was led by Pavol Amigo Dubovský from this observatory to also observe variable stars. Amigo taught me the basics of observing using CCD. Previously I considered variable stars to be a relatively unimportant field, but in Kolonica I found out that this is a very interesting field, and that amateur astronomers can do useful work. The experience gained here was later useful for my work with FRAM.

When did you discover your first variable star?

I discovered my first variable star in the spring of 2011. I observed from the balcony of our apartment in Liberec. I had a small simple CCD camera borrowed from Laco Balint (mentioned above), which I connected to a small 70/700 mm refractor. It was a random discovery within the observation of known eclipsing binary star. In the small field of view, besides a target star, there was another variable star, which was unknown yet. I was the first to discover its variability. Now it is listed in the CzeV catalog (Catalog of Variable Stars discovered by Czech astronomers) under number 245. Later I started to use a better set up, and so far I have found more than 200 new variable stars.

We can observe and hunt for new variable stars besides CCD camera also with more affordable digital single lens reflex camera (DSLR). Which type of device do you prefer for observations?

Now I prefer a camera which has undisputed advantages – a higher dynamic range, the possibility of active chip cooling, lower noise, higher sensitivity, etc. Disadvantage is, of course, a higher purchase price than a DSLR camera. Anyway, photometry of variable stars can be done very well with DSLRs. If you follow a few simple rules, the brightness measurements can also achieve the accuracy that is common for CCD cameras. I can recommend a DSLR for amateur astronomers or students who want to start collecting scientific data to help professional astronomers. During my study years, as I did not have enough money to buy my own CCD camera, I used DSLR camera for observations.

There is certainly no need to have professional equipment if you want to achieve valuable scientific results. Very modest amateur equipment is enough. Even a DSLR with a telephoto lens with a focal length of about 100 to 200 mm can be very useful. Data from amateur astronomers helps professional astrophysicists to reveal some secrets of variable stars, such as the overflow of matter from one star to another, another body in the system, etc. A number of amateur astronomers do not even know how valuable scientific data can be acquired by a conventional DSLR camera bought in second hand shop! Amateurs can this way observe brighter stars, which are too bright for bigger professional telescopes. A pleasant bonus is then the random discovery of new variable stars!

You have written detailed instructions for observing variable stars using DSLR together with Luboš Brat. Did this guide inspire others?

Yes, thanks to our article a couple of interested people were found and became active observers. They are consulting their observation procedures with me, I am always ready to answer their questions.

How many people do variable stars observations these days in Czech Republic and Slovakia?
There are several dozen people, many of whom I know personally. We hold various meetings – seminars, summer workshops and conferences. Meetings are important and in seminars and summer workshops, more experienced observers teach those who are less advanced. Professional astronomers also appear at these conferences, showing that the cooperation of amateurs and professionals is very important in the field of variable stars. Many amateurs are able to practically acquire professional data, amateurs are important co-authors of many scientific studies.

Where can newcomers meet you this year?

I'm taking part in most of thents organized by the Variable Star and Exoplanet Section of Czech Astronomical Society. To beginners interested in observing variable stars, I can recommend them to attend the summer workshop which we are currently organizing at the Observatory in Valasske Mezirici. We also organize weekend seminars during spring that focus on more advanced observers. In the fall, there is anual conference of the Variable Star and Exoplanet Section.

Alongwith the events organized by the Section of Variable Stars and Exoplanets, I also attend seminars under the auspices of the Society for Interplanetary Matter (SMPH). In addition, newcomers can meet me in various amateur astronomer sessions – during the beginning of the year it is an astro-meeting at Hodkovice nad Mohelkou, and in the spring at the Astroparty at Litice nad Orlicí. Furthermore, in the regular workshops organized by the Štefánik Observatory in Prague, and occasionally at the Summer Eition in Úpice, which is kind of a summer school of astronomy.

Those who are interested in variable star observation have a number of opportunities during the year where they can meet me. Of course there is also the possibility of individual personal meetings.

You were awarded the "Variable Star Observer 2016” by the Czech Astronomical Society for your activities in the field of variable stars. In 2015 you received another acknownledgement for your activities in astronomy – a minor planet was named after you. Which one is more important to you?

I very much appreciate both awards, but the named asteroid is more unique.

Do you remember the moment when you learned about the naming?

Yes I remember. My colleague, Michal Kusiak from Poland, wrote to me over chat to look at the latest list of named asteroids. I read the naming quotes of the asteroids one by one. After a while, I reached the planet number 6822 and saw the name of my friend and excellent astronomer Petr Horálek. I wrote congratulations to Peter. Only after that I noticed my name at minor planet 9841. I did not want to believe it at first. I very much appreciate this honor.

You became interested in astronomy as an 11-year boy in 1999, thanks to a total solar ecliphich you did not watch in the end. But you viewed the one in 2006 in Turkey. Last year you traveled to USA to see another one. After 11 years, you had the opportunity to experience this spectacular event again in the USA. Was it the same experience?

It is a very nice natural phenomenon that can shock you. I encourage everyone to go and see it at least once in a lifetime. During this second eclipse, I already knew what to expect, so the initial shock was not so big and I could push the camera shutter with a quiet hand and take a couple of nice pictures. Of course, I observed it both naked eyes and through binoculars. It was a gorgeous view of the solar corona and its structures. During the totality it is interesting to observe the landscape and colors of the Earth's atmosphere, especially on the horizon. I hope I will be able to see another total solar eclipse.

What else did you visit during your stay in the USA?

With my friends, we traveled through six states (California, Nevada, Arizona, Utah, Idaho, Wyoming) and visited 10 US national parks. During one month we drove over 10,000 km. I can recommend the western part of the USA, its countryside is beautiful.
Visit of Antelope Canyon, Arizona. Photo: Eliška Kabelková