Yuri Gagarin public astronomical observatory – the first in Bulgaria: 60 years later

The report presents an analysis of the history of the Public Astronomical Observatory (NAO) "Yuri Gagarin", the city of Stara Zagora, which was officially opened on February 26, 1961. The initiative to open it belongs to a group of enthusiasts, among which the figure of Boncho Bonev is of particular importance. With financial and material assistance from the municipality of Stara Zagora, the first premises were equipped and the first astronomical instruments and equipment were purchased. The observatory bears the name of the world's first pilot - cosmonaut Yuri Gagarin. The natural evolution of the development of the Observatory is presented, as well as the need of creation an observational base outside the city, in the area of the Ayazmo Park (opened in 1968). The supply with amateur telescopes is shown, as well as of a large optical instrument for professional astronomical work – a refractor (200/3000 mm), the Kude system, the production of the Carl Zeiss, Jena (former East Germany). The acquired ZKP-2 planetarium at the Carl Zeiss factory in Jena expands the NAO's capabilities in the education and promotion of astronomy and space science.The evolution of extracurricular astronomy training and the mass popularization of the achievements of astronomy, aeronautics, physics and human technology in PAOP are analyzed, as well as scientific observations of artificial Earth satellites. In this connection, in 1979 a specialized out-of-town observation base was built in the area of the Stara Zagora Mineral Baths, equipped with one of the most modern devices of its time – the AFU-75 satellite camera. An attempt was made to periodize the history of PAOP «Yu. Gagarin», the main stages being arranged in time according to significant historical, technological, organizational or other events.

Towards testing the theory of gravity with DESI: summary statistics, model predictions and future simulation requirements

Shortly after its discovery, General Relativity (GR) was applied to predict the behavior of our Universe on the largest scales, and later became the foundation of modern cosmology. Its validity has been verified on a range of scales and environments from the Solar system to merging black holes. However, experimental confirmations of GR on cosmological scales have so far lacked the accuracy one would hope for — its applications on those scales being largely based on extrapolation and its validity there sometimes questioned in the shadow of the discovery of the unexpected cosmic acceleration. Future astronomical instruments surveying the distribution and evolution of galaxies over substantial portions of the observable Universe, such as the Dark Energy Spectroscopic Instrument (DESI), will be able to measure the fingerprints of gravity and their statistical power will allow strong constraints on alternatives to GR. In this paper, based on a set of N-body simulations and mock galaxy catalogs, we study the predictions of a number of traditional and novel summary statistics beyond linear redshift distortions in two well-studied modified gravity models — chameleon f(R) gravity and a braneworld model — and the potential of testing these deviations from GR using DESI. These summary statistics employ a wide array of statistical properties of the galaxy and the underlying dark matter field, including two-point and higher-order statistics, environmental dependence, redshift space distortions and weak lensing. We find that they hold promising power for testing GR to unprecedented precision. The major future challenge is to make realistic, simulation-based mock galaxy catalogs for both GR and alternative models to fully exploit the statistic power of the DESI survey (by matching the volumes and galaxy number densities of the mocks to those in the real survey) and to better understand the impact of key systematic effects. Using these, we identify future simulation and analysis needs for gravity tests using DESI.

Taqī al-Dīn al-Rasid and His Treatise on Algebra Mathematical Evaluation, Translation, and Editio Princeps

Taqī al-Dīn al-Rāṣid is one of the most important representatives of the Ottoman tradition on mathematical sciences. His research focus being on astronomy, astronomical instruments, mathematics, optics, mechanics, and physics is understood from his surviving works. Taqī al-Dīn’s establishment and management of the Istanbul Observatory, which was the first observatory in the Ottoman Empire, made him an important figure in many ways. However, despite the aforementioned importance, the mathematics he learned, taught, produced and used has been a subject for very few studies. The primary way of determining the quality and the level of a work is to look at the kind of tools used for its creation. Therefore, this article will present the edition princeps, the translation and the evaluation of Taqī al-Dīn al-Rāṣid’s treatise on algebra, al-Nisab al-mutashākila fī ʻilm al-jabr wa-l-muqābala. It will be presented in the context of the idea that revealing a scientific character and the career of scholars who stand out in mathematical sciences can be possible by analyzing their mathematical works. The nature of the science of algebra, which can be applied to any problem encountered on any subject regardless of geometry or arithmetic, makes this idea more meaningful. For the correct examination of classical mathematical works, first the original text is verified and transformed into a format that provides an easy reading, then it is to be translated into the desired language. Finally a mathematical analysis and historical evaluation are needed to explain the main structure and justification of the content of the article.

Observational Instruments in the Arab Scientific Heritage Perspective Ismail ibn Heba Allah al-Hamawi | Al Alät Al Rosydiyyah fi At Thurost Al ‘Ilm Al ‘Aroby ‘Indä Ismäil ibn Hebä Allah al-Hämäwi

The article is an edited and critical study of an unpublished astronomical text entitled "The Astronomical Instrument Known as The Two-Pronged Machine" of a Damascene astronomer from the thirteenth century AD, Ismail ibn Heba Allah al-Hamawi. ancient scientific texts on this instrument are written by al-Kindi then Ibn Abbad and al-Nayrizi. Al-Kindi's text is the only text published from ancient texts, and today we present to researchers in the development of astronomical instruments a new text to contribute to enriching our knowledge of the scientific tradition of astronomical instruments in Islamic civilization.

Astrophotonics: Processing starlight

The field of astrophotonics has been fostering photonic innovations critical and unique to astronomical applications for several years. As we are about to embark on the new era of extremely large telescopes, astrophotonics is poised to become an integral part of the next generation astronomical instruments.

Why Couldn’t Muslim Astronomers Discover the Heliocentric System?

It comes to question the reasons why Muslim astronomers could not recognize the centrality of the Sun in the planetary system. While Europeans have spent centuries in their dark ages, Muslims spent the same centuries trying to verify the Ptolemaic planetary theory which has adopted the assumption of geocentricism, both theoretically and observationally. Many generations of Muslim astronomers from the 8th century to the 15th century lived circling in boring games of epicycles and deferments. Undoubtedly, Muslim astronomers devoted great efforts for developing the astronomical observations. For this purpose, they invented and developed many precise astronomical instruments and on the side of scientific literature, they wrote thousands of manuscripts in astronomy and observational techniques. This article questions the reasons why Muslim astronomers could not recognize the heliocentric system, despite their serious critique of the Ptolemaic geocentric model. For this purpose, we try to interrogate the astronomical manuscripts written by Muslim astronomers during the centuries before the Copernican breakthrough, since it is now believed that the efforts of Muslim astronomers have contributed great deal to the Copernican discovery of the heliocentric system. Some new studies in this area have already pointed to the fact that prominent Muslim astronomers have criticized the Ptolemaic geocentric system starting with the article of Ibn al-Haytham entitled “The Doubts about Ptolemy”, then al-Beruni’s assertion of the possibility of the spinning Erath while rotating around the Sun which comes in his assessment of the Indian astronomers' claim of the heliocentric model. The work of the astronomers of Muragha school and the Muragha observatory which was erected in 1259 and their models proposing to explain the observed planetary motions using the intelligent model of the “Tusi Couple”, in addition to the comments and suggestions of Ibn al-Shatir of Damascus about the lunar motion have contributed a great deal to the advancement of astronomy. These and many other flash points in the history of Islamic astronomy marked a strong zeal for a change that never took place. The question is: why could not Muslims adopt a new paradigm? This article emphasizes the fact that a transformation from the assumption of a geocentric system to a heliocentric system required a fundamental paradigm shift from the Aristotelian belief in the geocentric planetary system and the more developed Ptolemaic models. Such a paradigm was prevailing in the thoughts of Muslim philosophers as well as the religious clerics. We point to the fact that in addition to the observed reality of the celestial objects rotating around the Earth with different periods, the Aristotelian picture of the universe was in agreement with the interpretations of some verses of the Qur'an related to the celestial motion. We point here to the description of the heavenly spheres given by Ikhwan as-Safa who were a group of religious philosophers with some influence in the scientific circle. While being in doubt about the Ptolemaic models, Muslim astronomers were unable to continue their revolution to adopt a profoundly different model. The traditional understanding of some religious texts may have influenced the realization of some scientific facts. This may explain why Nasir al-Din al-Tusi, who belongs to the same sect of Ikwan as-Safa, resorted to device his couple to explain the apparently non-circular orbits of the planets by circular motion of his couple. However, we allude to the possibility that Muslim Mutakallimun could have achieved such a paradigm should they have the chance to continue their project on the Islamic worldview of nature. The endeavour of Mutakallimun to establish a rational and liberal attitude towards science and religion was negatively affected by their muddling with the theological question more than the questions related to natural philosophy. Internal fight between different factions of the Mutakallimun dispersed their efforts. Furthermore, the prohibition of kalam and the debates related to kalam aborted any progress in the rational approach to establish a scientific trend in religious studies. Keywords: Geocentric model, Heliocentric model, Ptolemy, Tusi couple, Islamic astronomy.

Starlight coupling through atmospheric turbulence into few-mode fibres and photonic lanterns in the presence of partial adaptive optics correction

ABSTRACT Starlight corrupted by atmospheric turbulence cannot couple efficiently into astronomical instruments based on integrated optics as they require light of high spatial coherence to couple into their single-mode waveguides. Low-order adaptive optics in combination with photonic lanterns offer a practical approach to achieve efficient coupling into multiplexed astrophotonic devices. We investigate, aided by simulations and an experimental testbed, the trade-off between the degrees of freedom of the adaptive optics system and those of the input waveguide of an integrated optic component leading to a cost-effective hybrid system that achieves a signal-to-noise ratio higher than a standalone device fed by a single-mode fibre.