2012 December Vol. 49 No 584
... the light pollution which most of us suffered today wherever we are in the world. However against this
simplistic comparison with today’s astronomers, those in the past did not necessarily have the same
quality optics even if of similar aperture. Also various aspects of the weather such as haze and ...
introduction to geodetic astronomy
... in the same natural system; therefore, to use this information for computations
in a geodetic system, the relationships must be known.
The astro-geodetic (relative) deflection of the vertical (a) at a
point is the angle between the astronomic normal at that point and the normal
to the reference elli ...
SOFA Astrometry Tools
... The positions of astronomical targets need to be expressed in diﬀerent ways for diﬀerent purposes. In the case of stars, and a terrestrial observer, three distinct needs have to be satisfied:
• A star catalog must describe the position in a way that is valid over a long period of time.
The usual met ...
GEK 1506 Heavenly Mathematics: Cultural Astronomy
... time shown on the clock at the central meridian of a given time zone, and the Earth's rate
of rotation is assumed to be constant. The civil time (shown on the clock) is based on the
Greenwich Mean Time (GMT) and is the region’s legally-accepted time scale based on
the standard time for that particul ...
EXPOSITION OF TIME
... It takes into account the requirements of consultants in the field of museum-pedagogy
referring to educational topics and interconnection to the system of education (RVP ZV).
Institutions and organisation concerned with the protection of the environment (MŽP) were
invited to join the exhibition and ...
A new method to determine the mean density of massive Solar
... distances to the Sun (Fig. 2); therefore their mean density trend is subtle. We allocate the
asteroids into two groups, according to the values of the mean density. The first group
includes a few asteroids with their mean densities higher than 4 g/cm 3. The mean densities of
these asteroids show the ...
(a) Mean solar time
... (α,δ) to the mean equator and equinox for the time
of observation, instead of the true equator and
equinox. The mean position still has the effects
of precession and proper motion included. This is
the position actually used in star catalogues. Mean
positions are quoted for a given epoch, e.g.
the orbits of neptune`s outer satellites
... movement that was not uniform and consistent like the Neptune
satellites over a 24 hr period. Because of the superior seeing on
consecutive nights in October, these images were the primary
ones used in our attempt to discover possible new satellites.
By placing artificial objects matched to the poin ...
Using the Heavens to Know Time to Using Time to Know the Heavens
... dictionary provides a definition of a clock as ‘a device other than a watch for indicating or
measuring time commonly by means of hands moving on a dial’ or broadly as ‘any periodic
system by which time is measured’.
To many in the present age, they would probably come in the form of a device with
Calculations of tithis
... Lunation is the time taken by the Moon to complete one revolution around the
Earth. The 360o angular path of the Moon in the sky is divided into 10,000 parts and 1
part, the finest possible resolution amounts 2.16 arc min (2.16 ). The time between two
conjunctions is a synodic lunar month. The small ...
Moon-Earth-Sun: The oldest three-body problem
... The three principal coordinate systems in the sky are
described in Sec. II; they are based on the local horizon,
on the equator, and on the ecliptic. The relations between these coordinate systems are fundamental for understanding the process of observing and interpreting
the results of the observat ...
Basic Solar Positional Astronomy
... Before atomic clocks, the problem with GMT was that
it was based on an imaginary mean Sun. Thus it was not
measurable, especially by navigators trying to calculate
longitude. They require an entirely uniform, definable
and measurable time scale that accords with the axis of
spin of the Earth and whi ...
Determination of accurate stellar radial
... ELODIE (Baranne et al. 1996) is an échelle spectrometer physically located in a coudé room at the 1.93 m telescope at Observatoire de Haute-Provence (OHP). For this programme, the spectrometer was fed via one optical fibre from
the Cassegrain focus. The instrument FWHM is '7.2 km s−1 ,
Differential rotation of the Sun
... Internal rotation in the Sun, showing differential rotation in the outer convective region and
almost uniform rotation in the central radiative region.
See also: Solar rotation
On the Sun, the study of oscillations revealed that rotation is roughly constant within the
whole radiative interior and v ...
a PDF version of the Uniglobe Manual.
... Azimuth. The horizontal angle between a reference direction and
another direction of interest. It is measured from 0° at the reference
direction clockwise or counter clockwise through 360.
... From a latitude of 40°, an object with a declination of +40° will, at some point in time during the
day or night, pass directly overhead through the zenith. In general
Declination at zenith = Latitude of observer
The 24 Ephemeris Stars in the SBO Catalog of Astronomical Objects have Object Numbers
Task - Illustrative Mathematics
... in the sky? Size and distance must play a role but are there other factors?
Are there other stars that are closer to the earth than Canopus but not as bright?
The light we see today in the sky from Canopus was emitted in the very early
1700's!!! If some important changes took place to the star Canop ...
Solar Radius Variations Measured in Central Eclipses
... one, modifying the time of bead’s dis/appearance and
the position of the shadow. Also a shift in lunar
latitude is possible.
In order to distinguish the contributions of lunar
longitude, latitude, solar longitude, lunar parallax and
UTC synchronization the residuals hi=Si-Mi SolarLunar limbs from ep ...
Telescopic Drawings or Photographs of Celestial
... • Two tasks that make up 25% of GCSE marks
• An unaided observation and an aided observation chosen from the approved list
• Unaided and aided observations can’t be from same row of approved list
• If more than one task completed the best mark counts
• Each task marked using the same markscheme givi ...
preprint, pdf version - LESIA
... the Earth radius in the predicted shadow paths. In addition, these
earlier predictions were degraded by the poorer precision of the
older Pluto ephemerides.
To overcome the problems faced by these first prediction eﬀorts, we used more modern facilities, namely the most
up-to-date CCD detectors, refe ...
SU3150-Astronomy - Michigan Technological University
... they too are not suitable as universal coordinates
To an observer in the northern hemisphere (of earth), all stars having north declinations are
visible but only some south stars are visible depending on the location of the observer
The scenario is reversed for observers on the southern hemisphere
Section 1.2 Astrometric Data
... • positions and proper motions are given for the catalogue epoch, T0 = J1991.25(TT), which is close
to the central epoch of observations (the distinction between the epoch which specifies the equinox
and equator of a coordinate system, typically B1950 or J2000, and the epoch at which the star passed ...
NJIT Physics 320: Astronomy and Astrophysics
... Statistics of sunspot number
by Swiss astronomer Rudolf
Relative sunspot number:
r = k (f + 10 g),
where g is the number of
sunspots groups visible on the
solar disk, f is the number of
individual sunspots (including
those distinguishable within
groups), and k is a correction
VARIOUS MEASUREMENTS OF TIME
... Since the earth rotates on its axis from west to east, all heavenly bodies (i.e. the sun
and the fixed stars) appear to revolve from east to west (i.e. in clock-wise direction) around
the earth. Such motion of the heavenly bodies is known as apparent motion. We may consider
the earth to turn on it a ...
On the definition and use of the ecliptic in
... 1) The adoption of the ICRS and ICRF (IAU 1997 Resolution B2)
International Celestial Reference System (ICRS)*: the idealized barycentric coordinate
system to which celestial positions are referred. It is kinematically non-rotating with respect to the
ensemble of distant extragalactic objects. It h ...
The term ephemeris time (often abbreviated ET) can in principle refer to time in connection with any astronomical ephemeris. In practice it has been used more specifically to refer to: a former standard astronomical time scale adopted in 1952 by the IAU, and superseded in the 1970s. This time scale was proposed in 1948, to overcome the drawbacks of irregularly fluctuating mean solar time. The intent was to define a uniform time (as far as was then feasible) based on Newtonian theory (see below: Definition of ephemeris time (1952)). Ephemeris time was a first application of the concept of a dynamical time scale, in which the time and time scale are defined implicitly, inferred from the observed position of an astronomical object via the dynamical theory of its motion. a modern relativistic coordinate time scale, implemented by the JPL ephemeris time argument Teph, in a series of numerically integrated Development Ephemerides. Among them is the DE405 ephemeris in widespread current use. The time scale represented by Teph is closely related to, but distinct (by an offset and constant rate) from, the TCB time scale currently adopted as a standard by the IAU (see below: JPL ephemeris time argument Teph).Most of the following sections relate to the ephemeris time of the 1952 standard.An impression has sometimes arisen that ephemeris time was in use from 1900: this probably arose because ET, though proposed and adopted in the period 1948–1952, was defined in detail using formulae that made retrospective use of the epoch date of 1900 January 0 and of Newcomb's Tables of the Sun.The ephemeris time of the 1952 standard leaves a continuing legacy, through its ephemeris second which became closely duplicated in the length of the current standard SI second (see below: Redefinition of the second).