One of the main findings that the Z Cam campaign brought is that collecting enough data in Central Europe takes a great deal of time due to the small number of usable nights. A second point is that it is still unclear to what extent data taken in places with light pollution are usable. The response to these facts is to place telescopes in a better location. What follows is information about the steps recently taken in this direction.
The beginning of the story of Slovak telescope hosting in Andalusia
After a long-term survey on the island of Madeira, which culminated in an expedition of potential stakeholders in autumn 2024, I decided to look for another way to provide Slovak astronomers with high-quality skies. The expedition to Madeira and, above all, the data we finally managed to obtain showed that Madeira is not entirely ideal for our purposes. The number of clear nights does not exceed 180 per year and is concentrated in the summer period even more than, for example, in Kolonica. Light pollution is increasing. Seeing data from recent years does not exist. Tourist pressure is rising. What remains are the advantages of geographic position, already established contacts, and, of course, the pleasant climate. The expedition itself did not leave a good impression on the participants due to the completely unsuitable weather. All this led me to step back and look for the objectively most advantageous location. Many factors come into play with such a choice, so it is difficult to set truly objective criteria. Moreover, much depends on the goals we set.
So I said to myself that the goal is to build a telescope-hosting site primarily intended for astrophotographers who will take part in “deep imaging” campaigns such as the one currently underway to search for super-remnants of novae (Nova Super-remnant, astrofoto.astrokolonica.sk). I set the criteria as follows:
| Criterion | Weight |
|---|---|
| Dark sky | 20 |
| Number of clear nights | 20 |
| Latitude below 40° | 10 |
| Seeing | 10 |
| On-site climate pleasant for operators | 5 |
| Transport accessibility | 5 |
| Internet availability | 10 |
| Availability of electricity and water | 5 |
| Local support | 10 |
| Options for accommodation and permanent living | 5 |
In the next phase came searching the map. Particularly useful was www.lightpollutionmap.com. Among other things, it can also display existing observatories. That is how I found Piconcillo—a village near the literature-famous Fuente Obejuna. In Piconcillo, there are two domes belonging to amateur astronomers. I wrote to the one with the French-sounding name, expecting a more responsive answer than from the local resident, who is also the chairman of the astronomy club. The reply was enthusiastic enough, and so we agreed on a first exploratory visit.
Report from the first trip to Piconcillo
It took place from 30 April to 7 May 2025. It began impressively at the celebrations of 50 years of the Asociación Malagueña de Astronomía. As I later learned, there are two associations in Málaga that compete with each other. In any case, the meeting was pleasant, with a dinner at which I was able to meet the organization’s leadership. Most useful, however, was getting to know Alberto Castro-Tirado, head of the BOOTES network of robotic telescopes. As a result, I was invited to the 9th workshop on the use of robotic telescopes, to be held in the autumn in Almería.
The next day, we moved with Hubert Delanuy to Piconcillo. Hubert is the owner of one of the observatories in the village. He welcomed me generously. We first spent the night at his house in Málaga, and then he hosted me at the observatory, which is one of the family houses in Piconcillo.
Getting to know the site involved the following:
– Tour of Hubert’s observatory (ScopeDome dome not working, GM3000 mount, 20″ Dall-Kirkham Planewave, QHY CMOS).
– Meeting the chairman of the Asociación Astronómica de Piconcillo, Francisco Manuel Santos. The association has ~30 members, 4 of them active. Francisco works at the municipal office in Fuente Obejuna, knows local conditions, and can find landowners, but he was ill, so we met only once at the end of the stay; a meeting with the mayor will be next time.
– Daytime tour of the village. Both domes are inside the village, so I assumed the light pollution from local lighting would be reasonable.
– Evening inspection showed that the public lighting is indeed a pleasant warm color, but it is too intense and also shines into the upper hemisphere.
– Daytime tour of the surroundings of the village, searching for potentially suitable places. Analysis of the Spanish cadastre—works excellently, but the owner is not shown. The surroundings are mostly large farms. Finding a plot is surprisingly difficult.
– Morning inspection of the selected site (after moonset and with low cloud). From the north, the village of Argallón, 1 km away, shines a little.
– Meeting with an architect. She acquainted us with the provincial and municipal regulations that govern what can be built outside the built-up area on agricultural land. She promised to prepare a quotation for a building design for pavilions similar to the astrophotography pavilion at Kolonica Saddle.
– Visit to the LAINEZ real-estate office in the town of Peñarroya. The selected plot is for sale, but is unnecessarily large (7 ha) and costs €60,000. A smaller plot 1 km south of the village of Posadillas is also for sale for €38,000.
– Morning inspection of the plot near Posadillas. The village shines unexpectedly strongly and white. It would be better to be a bit farther from it. A request was sent to the real estate agency to find something farther south.
– Final meeting with Francisco. He is very keen for the telescope-hosting project to be in Piconcillo. He promised to find a suitable plot near the village but on the other side of the hill, in order to eliminate the influence of the village’s public lighting.
– Evaluation of seeing based on Hubert’s images. It is under 3″ even at low altitudes around 30°. (He observes main-belt asteroids, so he doesn’t aim much at the zenith.)
Based on the findings obtained, I prepared a SWOT analysis of the telescope-hosting project in Piconcillo
| Strengths | Weaknesses |
| – Language, comfortable communication in Spanish – The concept of telescope hosting is not unknown here – Accommodating approach of all local contacts (Alberto, Hubert, Francisco, the architect, the real-estate agency, Blanca, Rosa, Juanma from AMA) – Transport accessibility is good (Málaga – plane, Córdoba – high-speed train, Fuente Obejuna – bus) – Peñarroya is a nice town to live in – In the villages there are casas rurales for housing astro-tourists – Urban-planning rules will not allow building just anything – The population mostly moved away after the mines closed – Astro-climate is fine | – Hard to find a plot – Lighting is strong even in the villages – A car will be needed during construction – Seeing does not reach island-class values – High summer temperatures – Wells must be dug to 60 m depth – Everything is fenced; a sense of freedom is lacking |
| Opportunities | Threats |
| – E-Eye hosting has a brighter sky – Hosting with the darkest sky in Spain — we can promote the project that way – Reconstruction of public lighting, or switching off every other lamp – 80% of the land must be used in a non-building way, e.g., for agriculture | – Climate change (at the time of the stay, an unprecedented two-month period of rain had just ended) – Re-opening of the mines – The hosting site will need to be guarded against vandalism – Foreigners are buying many properties in Spain – The radioactive-waste repository in Cabril glows when unloading material |
The quantified evaluation is in the following table:
| Criterion | Weight | Rating | Points |
|---|---|---|---|
| Dark sky (Bortle 2) | 20 | 0.8 | 16 |
| Number of clear nights (250) | 20 | 0.7 | 14 |
| Latitude between 28° and 50° (38°) | 10 | 0.6 | 6 |
| Seeing (2″) | 10 | 0.8 | 8 |
| On-site climate pleasant for operators | 5 | 0.8 | 4 |
| Transport accessibility | 5 | 0.6 | 3 |
| Internet availability | 10 | 0.8 ? | 8 |
| Availability of electricity and water | 5 | 0.6 ? | 3 |
| Local support | 10 | 0.9 | 9 |
| Options for accommodation and permanent living | 5 | 0.8 | 4 |
| 75 |
Ratings with a question mark are indeterminate; they depend on the choice of the plot.
For comparison, the evaluation of AO Kolonické sedlo according to the same criteria
| Criterion | Weight | Rating | Points |
|---|---|---|---|
| Dark sky (Bortle 3) | 20 | 0.6 | 12 |
| Number of clear nights (100) | 20 | 0.3 | 6 |
| Latitude between 28° and 50° (49°) | 10 | 0.1 | 1 |
| Seeing (3.5″) | 10 | 0.5 | 5 |
| On-site climate pleasant for operators | 5 | 0.4 | 2 |
| Transport accessibility | 5 | 0.6 | 3 |
| Internet availability | 10 | 0.9 | 9 |
| Availability of electricity and water | 5 | 0.8 | 4 |
| Local support | 10 | 0.9 ? | 9 |
| Options for accommodation and permanent living | 5 | 0.8 | 4 |
| 56 |
Ratings with a question mark are indeterminate; they depend on the staffing of the Vihorlatská Observatory.
Pavol A. Dubovský