arXiv subjects

Andreas Schrimpf

Publications and source records attributed to Andreas Schrimpf.

18 recordsLinked to original sources

arXiv2026

Computing Natural Magnitudes in the Photometric Systems of Astronomical Plates using Gaia DR3 SEDs

Context. Accurate photometric calibration of astronomical photographic plates remains a fundamental challenge in astronomy, especially when bridging historical photographic data with modern observations due to the mismatch of spectral sensitivities of photographic plates and passbands of modern calibration catalogs. Aims. We intend to derive consistent natural magnitudes for celestial sources within the intrinsic photometric systems of astronomical photographic plates by using Gaia Data Release 3 (DR3) blue photometer (BP) and red photometer (RP) low-resolution spectral data and to show its superiority to former methods. Methods. We compiled spectral characteristic data for emulsions and filters applied in photometric observations using glass plates. The collected color sensitivities, modified by atmospheric reddening depending on the air mass, are then used to compute accurate natural magnitudes and fluxes of objects in the photographic plates through synthetic photometry, utilizing a catalog of Gaia spectral energy distributions (SEDs) over the wavelength range 330 nm to 1050 nm (XP spectra). This process uses GaiaXPy, a Python library designed to handle Gaia DR3 spectral data. These natural magnitudes are then compared with results from the color term method used to compile the data in existing photoplate archives. Results. Comparing the synthetic magnitudes with those existing in the Archives of Photographic PLates for Astronomical USE (APPLAUSE), we were able to reveal systematic errors of the existing data in the range of +/-0.3 mag and higher. In addition, the presented method allows for an accommodation of stars with similar color index but of different luminosity classes as well as an effective correction of atmospheric reddening at higher air masses, approximately 0.2 mag.

astro-ph.IM↗

arXiv2025

Commissioning an Inexpensive Off-the-shelf Spectrograph for Radial-Velocity Studies

We present a way to set up an inexpensive out of the shelf spectrograph at a local observatory. Stability and resolution of the spectrograph are high enough for radial velocity determination of binary stars or determination of stellar characteristics. Even some exoplanets might be detectable via the radial velocity method.

astro-ph.IM↗

arXiv2024

History of the Observation of Stars

There are about 6000 stars, that can be seen with the naked eye and have been observed for centuries for various purposes. More modern investigations using advanced telescopes show that our Milky Way, a quite common galaxy, consists of about 100 -- 400 billion stars. And, it is estimated that there are between 200 billion to 2 trillion galaxies in the observable universe -- all of them consist mostly of stars, and sending observable signals which also represents nothing more than a superposition of the light of individual stars. So we can conclude that the most common observable objects in the Universe are $\textit{stars}$. In this chapter, we focus on the long history of the observation of stars (compared to studies in other fields of science) to find out more about the nature of these objects.

astro-ph.SR↗

arXiv2023

Prospect of Plate Archive Photometric Calibration by GAIA SED Fluxes

This study aims to improve the photometric calibration of astronomical photo plates. The Sonneberg Observatory's sky patrol was selected, comprising about 300,000 plates, and the digitization workflow is implemented using PyPlate. The challenge is to remove zero point offsets resulting from differences in color sensitivity in the photo plates' emulsion response. By utilizing the Gaia DR3 dataset and the GaiaXPy tool, we are able to obtain a consistent astrometric and photometric calibration of the Sonneberg plates and those of other archives such as APPLAUSE.

astro-ph.IM↗

arXiv2022

Persuasion by Dimension Reduction

How should an agent (the sender) observing multi-dimensional data (the state vector) persuade another agent to take the desired action? We show that it is always optimal for the sender to perform a (non-linear) dimension reduction by projecting the state vector onto a lower-dimensional object that we call the "optimal information manifold." We characterize geometric properties of this manifold and link them to the sender's preferences. Optimal policy splits information into "good" and "bad" components. When the sender's marginal utility is linear, revealing the full magnitude of good information is always optimal. In contrast, with concave marginal utility, optimal information design conceals the extreme realizations of good information and only reveals its direction (sign). We illustrate these effects by explicitly solving several multi-dimensional Bayesian persuasion problems.

stat.ML↗

arXiv2021

The star catalogue of Wilhelm IV, Landgraf von Hessen-Kassel

Near the end of the 16th century Wilhelm IV, Landgraf von Hessen-Kassel, set up an observatory with the main goal to increase the accuracy of stellar positions primarily for use in astrology and for calendar purposes. A new star catalogue was compiled from measurements of altitudes and angles between stars and a print ready version was prepared listing measurements as well as equatorial and ecliptic coordinates of stellar positions. Unfortunately, this catalogue appeared in print not before 1666, long after the dissemination of Brahe's catalogue. With the data given in the manuscript we are able to analyze the accuracy of measurements and computations. The measurements and the computations are very accurate, thanks to the instrument maker and mathematician Jost Bürgi. The star catalogue is more accurate by a factor two than the later catalogue of Tycho Brahe.

astro-ph.IM↗

arXiv2021

Optimal Transport of Information

We study the general problem of Bayesian persuasion (optimal information design) with continuous actions and continuous state space in arbitrary dimensions. First, we show that with a finite signal space, the optimal information design is always given by a partition. Second, we take the limit of an infinite signal space and characterize the solution in terms of a Monge-Kantorovich optimal transport problem with an endogenous information transport cost. We use our novel approach to: 1. Derive necessary and sufficient conditions for optimality based on Bregman divergences for non-convex functions. 2. Compute exact bounds for the Hausdorff dimension of the support of an optimal policy. 3. Derive a non-linear, second-order partial differential equation whose solutions correspond to regular optimal policies. We illustrate the power of our approach by providing explicit solutions to several non-linear, multidimensional Bayesian persuasion problems.

econ.GN↗

arXiv2021

The star catalogue of Wilhelm IV, Landgraf von Hessen-Kassel: Accuracy of the catalogue and of the measurements

We analyse a manuscript star catalogue by Wilhem IV, Landgraf von Hessen-Kassel, from 1586. From measurements of altitudes and of angles between stars, given in the catalogue, we find that the measurement accuracy averages 26 arcsec for eight fundamental stars, compared to 49 arcsec of the measurements by Brahe. The computation in converting altitudes to declinations and angles between stars to celestial position is very accurate, with errors negligible with respect to the measurement errors. Due to an offset in the position of the vernal equinox the positional error of the catalogue is slightly worse than that of Brahe's catalogue, but when correction is made for the offset -- which was known to 17th century astronomers -- the catalogue is more accurate than that of Brahe by a factor two. We provide machine-readable Tables of the catalogue.

astro-ph.IM↗

arXiv2019

Research on asteroids of Christian Ludwig Gerling and his students in the nineteenth century

One of the mayor topics in astronomy at the beginning of the 19th century was the interpretation of the observations of the first asteroids. In 1810 Christian Ludwig Gerling at the age of twenty two came to Göttingen University to continue his academic studies. Supervised by Carl Friedrich Gauß at the observatory he was engaged in studies of theoretical and practical astronomy. Starting in 1812 Gerling accepted the responsibility for collecting observational data of the asteroid Vesta from the European observatories and for calculating the ephemeris of this new minor planet. In 1817 Gerling was appointed professor at Marburg University. One of his early astronomical projects in Marburg was his contribution to the Berliner Akademische Sternkarten. After completion of his observatory in 1841 Gerling's students started observing and theoretically analysing the orbits of the continuously newly discovered asteroids including the perturbation of the larger solar system bodies. The observations at Gerling's observatory are the first astrometric measurements of solar systems minor bodies of Hesse.

physics.hist-ph↗

arXiv2017

Victorinus Schönfeldt (1533 - 1591) und sein "Prognosticon Astrologicum"

Annual astrological calendars, practica and prognostications became widespread publications in Europe after the invention of printing presses in the 15th century. Using the national language instead of Latin, the language of the scientists, the motion of sun, moon and planets were explained and used to foretell weather, growth of fruit, diseases, war and misfortune. By this means astronomical knowledge became accessible to everyone capable of reading. A milestone in the context of position calculations of bodies of our solar system was the publication of the Copernican system in 1543. When Victorinus Schönfeldt started his studies at Wittenberg University he was educated in the so called "Wittenberg Interpretation" of Copernicus. In 1557 Schönfeldt became professor of mathematics at Marburg University and in 1566 he additionally was given a professorship of medicine With the help of his teachers and mentors in Wittenberg Schönfeldt was introduced to the court of the landgrave of Hessen in Marburg and became a close friend to the noble family. To Wilhelm IV., landgrave of Hessen-Kassel from 1567, he served not only as one of the personal physicians but as a scientific counselor in the landgraves' astronomical studies. Presumably right after being appointed a professor of mathematics Schönfeldt began to write his "\emph{Prognosticon Astrologicum}", a series of annual books, that he continued until his death. He made use the Copernican system for his calculations, comparing them occasionally with calculations using new Ptolemaic based ephemerides and in his last almanacs with calculations based on Tycho Brahes' model.

physics.hist-ph↗

arXiv2016

Sonneberg Sky Patrol Archive - Photometric Analysis

The Sonneberg Sky Patrol archive so far has not yet been analyzed systematically. In this paper we present first steps towards an automated photometric analysis aiming at the search for variable stars and transient phenomena like novae. Early works on the sky patrol plates showed that photometric accuracy can be enhanced with fitting algorithms. The procedure used was a manually supported click-and-fit-routine, not suitable for automatic analysis of vast amount of photographic plates. We will present our progress on deconvolution of overlapping sources on the plates and compare photometric analysis using different methods. Our goal is to get light curves of sufficient quality from sky patrol plates, which can be classified with machine learning algorithms. The development of an automated scheme for finding transient events is in progress and the first results are very promising.

astro-ph.IM↗

arXiv2016

Hans Wolter - a pioneer of applied optics

Applied optics was one of the major topics Hans Walter was engaged in during his scientific life. He contributed to the understanding of optical properties of thin films, which could be used to design coating layers to improve the properties of optical and other surfaces. He developed the theoretical description of the basic principles of phase-contrast, schlieren and interference optics applied to enhance low contrast details and to increase the resolution in studies of biological samples. And last, but not least, Hans Wolter proposed an optical system of two grazing--incidence mirrors for use in an X--ray imaging microscope. A microscope using such an optics never was put into practice, but the optical design turned out to be well suited for telescopes.

physics.hist-ph↗

arXiv2015

Die Gerling Sternwarte (Gerling Astronomical Observatory)

Christian Ludwig Gerling's 1817 appointment as Professor for Mathematics, Physics and Astronomy resulted in the foundation of the Mathematical and Physical Institute of the Philipps University. In 1838, Gerling moved onto new premises in the main building of the former Dörnberger Hof in Renthof Street where the Philipps University's astronomical observatory was installed in the upper part of the old tower in 1841. The most important device at that time was a transit instrument which served to measure the transit times of stars in the meridian. Precise alignment required the use of a meridian stone, an artificial point of reference exactly north of and at about four kilometers' distance from the observatory. The scientists observed planets and their moons, the asteroids that were only discovered at the beginning of the 19th century, and some fainter stars in order to improve stellar charts. The Gerling Observatory is the first place in Hesse, where positions of asteroids were read.

physics.hist-ph↗

arXiv2015

Die Physikalische Sammlung (Physical Collection)

At the end of the 17th century, the collection was established through the acquisition of Leiden instrumentmaker Musschenbroek's collection. Its aim was to demonstrate physical phenomena. Until the end of the 18th century, the collection was used and extended by a number of professors from various university departments in teaching mechanics, hydrostatics, optics and electrostatics. The foundation of the Institute for Mathematics and Physics in 1817 and the appointment of Christian Ludwig Gerling to the position of Professor for Mathematics, Physics and Astronomy strengthened the subject considerably. Gerling extended the collection mainly with devices for geodesy and astronomy, with more instruments being added in the time up to the middle of the 20th century. Today, the collection allows an insight into the history of scientific instruments as witnesses of the past.

physics.hist-ph↗

arXiv2014

The first measurement of the deflection of the vertical in longitude -- The figure of the earth in the early 19th century

During the summer of 1837 Christian Ludwig Gerling, a former student of Carl Friedrich Gauß's, organized the world wide first determination of the deflection of the vertical in longitude. From a mobile observatory at the Frauenberg near Marburg (Hesse) he measured the astronomical longitude difference between C.F. Gauß's observatory at Göttingen and F.G.B. Nicolai's observatory at Mannheim within an error of 0.4". To achieve this precision he first used a series of light signals for synchronizing the observatory clocks and, second, he very carefully corrected for the varying reaction time of the observers. By comparing these astronomical results with the geodetic--determined longitude differences he had recently measured for the triangulation of Kurhessen, he was able to extract a combined value of the deflection of the vertical in longitude of Göttingen and Mannheim. His results closely agree with modern vertical deflection data.

physics.hist-ph↗

arXiv2014

An international campaign of the 19th century to determine the solar parallax - The US Naval expedition to the southern hemisphere 1849 - 1852

In 1847 Christian Ludwig Gerling, Marburg (Germany), suggested the solar parallax to be determined by measuring the position of Venus close to its inferior conjunction, especially at the stationary points, from observatories on nearly the same meridian but widely differing in latitude. James M. Gilliss,astronomer at the newly founded U.S. Naval Observatory, enthusiastically adopted this idea and procured a grant for the young astronomical community of the United States for an expedition to Chile. There they were to observe several conjunctions of Venus and oppositions of Mars, while the accompanying measurements were to be taken at the US Naval Observatory in Washington D.C. and the Harvard College Observatory at Cambridge, USA. This expedition was supported by A. v. Humboldt, C.F. Gauß, J.F. Encke, S.C. Walker, A.D. Bache, B. Peirce and others. From 1849 to 1852 not only were astronomical, but also meteorological and magnetic observations and measurements recorded, mainly in Santa Lucia close to Santiago, Chile. By comparing these measurements with those taken simultaneously at other observatories around the world the solar parallax could be calculated, although incomplete data from the corresponding northern observatories threatened the project's success. In retrospect this expedition can be recognized as the foundation of the Chilean astronomy. The first director of the new National Astronomical Observatory of Chile was Dr. C.W. Moesta, a Hessian student of Christian Ludwig Gerling's. The exchange of data between German, American and other astronomers during this expedition was well mediated by J.G. Flügel, consul of the United States of America and representative of the Smithsonian Institution in Europe, who altogether played a major role in nurturing the relationship between the growing scientific community in the U.S. and the well established one in Europe at that time.

physics.hist-ph↗

arXiv2013

Die weltweit erste Messung einer Lotabweichung in der Länge

During the summer of 1837 Christian Ludwig Gerling, a former student of Carl Friedrich Gauss, organized the world wide first determination of a vertical deflection in longitude. From a mobile observatory at the Frauenberg close to Marburg (Hessen) he measured the astronomical longitude difference between the observatory of C.F. Gauss at Göttingen and the observatory of F.G.B. Nicolai at Mannheim. By comparing these astronomical results with the geodetic determined longitude differences, which he just had measured as a part of the triangulation of Kurhessen, he was able to extract a combined value of the vertical deflection of Göttingen and Mannheim. His results are in very good agreement with modern vertical deflection data.

physics.hist-ph↗

arXiv2013

Geometrie und Astronomie im Stadtplan des hethitischen Sarissa

The Hittite city Sarissa was founded in the 16th century BC and has been systematically constructed. The city gates and the bigger public buildings were arranged at about 45° relative to the cardinal directions. However, one of the temples features a remarkable deviation from this general orientation. The following analysis shows that both, the general orientation of the public buildings and the deviation of one of the temples are related to astronomical observations, particularly to the course of the sun, and maybe also to some special points of the course of the Venus.

physics.hist-ph↗