Related papers: Uffenbach's "Zeitweiser" published 1598
Much of our knowledge about the solar dynamo is based on sunspot observations. It is thus desirable to extend the set of positional and morphological data of sunspots into the past. Gustav Sp\"orer observed in Germany from Anklam…
The Hirsch conjecture was posed in 1957 in a letter from Warren M. Hirsch to George Dantzig. It states that the graph of a d-dimensional polytope with n facets cannot have diameter greater than n - d. Despite being one of the most…
Pope Clement XI (1700-1721) ordered Francesco Bianchini (1662-1729) to build a Meridian Line. Bianchini was the Secretary of the Commission for the Calendar. He chose the Basilica of Santa Maria degli Angeli because of the stability of its…
Digitized images of the drawings by J.C. Staudacher were used to determine sunspot positions for the period of 1749-1796. From the entire set of drawings, 6285 sunspot positions were obtained for a total of 999 days. Various methods have…
This article presents the results of a study of signs on a Bronze Age slab discovered in the vicinity of a heavily plowed mound near the settlement of Pyatikhatki. The slab belongs to the Dolmen archaeological culture. In the course of this…
Astrometry, the most ancient branch of astronomy, was facing extinction during much of the 20th century in the competition with astrophysics. The revival of astrometry came with the European astrometry satellite Hipparcos, approved by ESA…
The focal field properties of radially/azimuthally polarized Zernike polynomials are studied. A method to design the pupil field in order to shape the focal field of radially or azimuthally polarized phase vortex is introduced. With this…
In this paper we analyze, discuss and present the design of the Antikythera Mechanism s central front parts. Based on the aligned and of same scale visual images of Fragment C front/back face and the X-ray CT scacs, we designed and…
"El Cielo de Salamanca" ("The Sky of Salamanca") is a quarter-sphere-shaped vault 8.70 metres in diameter. It was painted sometime between 1480 and 1493 and shows five zodiacal constellations, three boreal and six austral. The Sun and…
A long time-series of sunspot observations is preserved from Samuel Heinrich Schwabe who made notes and drawings of sunspots from 1825-1867. Schwabe's observing records are preserved in the manuscript archives of the Royal Astronomical…
This paper presents an analysis of the star atlas included in the medieval Chinese manuscript (Or.8210/S.3326), discovered in 1907 by the archaeologist Aurel Stein at the Silk Road town of Dunhuang and now held in the British Library.…
We have been doing a photometric and astrometric sample survey programme on Schmidt plates in a few selected directions in the Galaxy with an aim to study galactic stellar populations. In order to calibrate Schmidt plates photometrically,…
The use of the observed positions of celestial bodies to determine the location of a navigator and to direct vessels, was an aspiration of ancient seafarers. Various peoples, in the Mediterranean as much as in the Indian Ocean, in China as…
The images of sunspots in sixteen active regions taken at the UCCI Observatory in Grand Cayman during June - November 2015, were used to determine their fractal dimensions using the perimeter-area method for the umbral and the penumbral…
A good candidate for a polar-ring galaxy has been detected in the Hubble Ultra Deep Field (HUDF). The galaxy HUDF 1619 (V~25 mag, z~1) is the most distant object of this type known to date. A large-scale structure crosses the highly warped…
Catalogs of the Zurich Observatory contain positional information on sunspots, prominences and faculae in late 19th and early 20th centuries. This database is given in handwritten tabular form and was not systematically analysed earlier. It…
It has long been conjectured that the Euclidean Schwarzschild and Euclidean Kerr instantons are the only non-trivial asymptotically flat (AF) gravitational instantons. In this letter, we show that this conjecture is false by explicitly…
Photon surfaces are timelike, totally umbilic hypersurfaces of Lorentzian spacetimes. In the first part of this paper, we locally characterize all possible photon surfaces in a class of static, spherically symmetric spacetimes that includes…
This article proposes a mathematical model of an inverted analemmatic sundial, provides formulas for calculating the coordinates of their hour markers. On the example of the Belogorsk sundial, a method is described for determining the…
We made optical observations of the Gegenschein using a liquid-nitrogen-cooled wide-field camera, Wide-field Imager of Zodiacal light with ARray Detector (WIZARD), between March 2003 and November 2006. We found a narrow brightness…