Related papers: A Brief History of Astronomical Brightness Determi…
The reports from 2008: "Astrometry and optics during the past 2000 years", are available at arXiv and at my website: www.astro.ku.dk/~erik/History.pdf . Here are now further contributions to the history of astrometry related to space…
The satellite missions Hipparcos and Gaia by the European Space Agency will together bring a decrease of astrometric errors by a factor 10000, four orders of magnitude, more than was achieved during the preceding 500 years. This modern…
The history of astrometry, the branch of astronomy dealing with the positions of celestial objects, is a lengthy and complex chronicle, having its origins in the earliest records of astronomical observations more than two thousand years…
The great development of astrometric accuracy since the observations by Hipparchus about 150 BC was documented in 2008 in the first version of the present report. This report was updated in H{\o}g (2017d), e.g. with recent information on…
This pedagogical document about stellar photometry - aimed at those for whom astronomical arcana seem arcane - endeavours to explain the concepts of magnitudes, color indices, absolute magnitudes, distance moduli, extinctions, attenuations,…
Large constellations of artificial satellites are beginning to interfere with astronomical observing. Visual magnitude measurements of these spacecraft are useful for monitoring and characterizing their brightness. This paper describes the…
The great development of astrometric accuracy since the observations by the Greek astronomer Hipparchus about 150 BC has often been displayed in diagrams showing the accuracy versus time. Two new diagrams are provided here, one for…
Astrometry provides the foundation for astrophysics. Accurate positions are required for the association of sources detected at different times or wavelengths, and distances are essential to estimate the size, luminosity, mass, and ages of…
Image sensors, most notably the Charge Coupled Device (CCD), have revolutionized observational astronomy as perhaps the most important innovation after photography. Since the 50th anniversary of the invention of the CCD has passed in 2019,…
First proposed by Paczynski in 1986, microlensing has been instrumental in the search of compact dark matter as well as discovery and characterization of exoplanets. In this article, we provide a brief history of microlensing, especially on…
Astronomical observing has been greatly simplified by the development and implementation of digital imaging techniques and remote observing. Aperture photometry of CCD data permits photometric measurements to be made routinely with…
It is now less than a decade since CoRoT initiated the space photometry revolution with breakthrough discoveries, and five years since Kepler started a series of similar advances. I'll set the context for this revolution noting the status…
Astrometric observations of microlensing events were originally proposed to determine the lens proper motion with which the physical parameters of lenses can be better constrained. In this proceeding, we demonstrate that besides 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 application of photography to astronomy was a critical step in the development of astrophysics at the end of the nineteenth century. Using custom-built photographic telescopes and objective prisms, astronomers took images of the sky on…
The non-spherical shape of the Sun has been invoked to explain the anomalous precession of Mercury. A brief history of some methods for measuring solar diameter is presented. Archimedes was the first to give upper and lower values for solar…
We have summarized here the astronomical knowledge of the ancient Hindu astronomers. This knowledge was accumulated from before 1500 B.C. up to around 1200 A.D. In Section \ref{equiv} we have correlated terms used by the Hindu astronomers…
General relativistic effects in astrophyiscal systems have been detected thanks to accurate astrometric measurements. We outline some keystones of astrometry such as stellar aberration (argument development during the years 1727-1872);…
Astrometry as a technique has so far proved of limited utility when employed as either a follow-up tool or to independently search for planetary mass companions orbiting nearby stars. However, this is bound to change during the next decade.…
Ground-based optical astronomy necessarily involves sensing the light of astronomical objects along with the contributions of many natural sources ranging from the Earth's atmosphere to cosmological light. In addition, astronomers have long…