Quadrant 1570
400 Years of Astrometry :
From Tycho Brahe to Hipparcos
Sighting the star
Tycho Brahe’s
new
instruments
A technical and scientific development
Erik Høg, Niels Bohr Institute, Copenhagen University
Introduction of the telescope
Micrometers, divided circles, clocks
Space techniques
Updated 17 August 2009
Erik Høg
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Tycho Brahe
mural quadrant
One observer for the star,
two assistants for clocks,
circle and protocol
1000 stars measured
celestial reference frame
for measurement of planets
Tycho Brahe
on Hven
1576-97
A barrel of gold
Diagonal division lines
Sextant 1580
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Two telescopes
Some results from astrometry 16001600-1700
The Dutch telescope
Hans Lipperhey 1608
1602-1619 : Laws of planet orbits by Johannes Kepler
1602based on Tycho Brahe’s observations
Micrometer not possible
small field
field,, small magnifications
1611 : Orbits of the Jupiter satellites by Galileo Galilei
The Kepler telescope
Johannes Kepler 1611
1687 : Laws of dynamics and gravitation by Isaac Newton
1659 : Planet diameters measured by Christiaan Huygens
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Micrometer possible
possible:: wires at (5)
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Sextant and quadrant
Divided scales and circles
Hevelius, brass sextant
With naked eye open sight pinnules
until 1679, Johannes Hevelius
1674 Hevelius :
Scale with vernier
and diagonals
Telescopic sight on quadr.
quadr. and sext.
sext.
1640 by William Gascoigne
1665--, Robert Hooke a.o
1665
a.o..
The high art of
of dividing the circle
Mural ”quadrant
quadrant”” of 140 deg.
deg.
1689--, John Flamsteed
1689
(1990 book by Allan Chapman)
1658 : Pendulum clock by Christiaan
Huygens
1659 : Wire micrometer by Huygens
Gascoigne 1641, but known only later
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Transit instrument by Ole Rømer
Some results from astrometry 17001700-1800
1725 : The ’Great Catalogue’,
Catalogue’, 3000 stars, error 12”, by
John Flamsteed using a mural ”quadrant”
quadrant” of 140 deg
deg..
1728 : Aberration 20” and nutation 9” discovered by
James Bradley using a zenith sector with precision 1”
1675 - Transit instrument
in Copenhagen
1737 : Flattening of the Earth measured
measured,, P.L.M.
Maupertuis
1767 : Binaries predicted statistically by John Michell;
1779… : Systematic observations by W. Herschel
Herschel;;
1827 : First orbit by Felix Savary
1781 : Uranus discovered by William Herschel
1783 : William Herschel:
Herschel: motion of Sun towards Hercules
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Mural quadrant – John Bird - 1773
Meridian circle by Ole Rømer
Hevelius
Critical issues :
Divisions
Planarity of circle
1705 - Meridian circle
full circle and microscopes
Only after 1800 were quadrants
out of business
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Jesse Ramsden
Some results from astrometry 18001800-1900
Dividing machines
1801 : First asteroid,
asteroid, Ceres, discov
discov.. by Guiseppe Piazzi
1838 : Parallax of stars by Bessel,
Bessel, Henderson, Struve
1850 : 20 parallaxes in a catalogue by Peters
Lathes to make round
mechanical parts, screws
1837 : From 390 proper motions Argelander : solar apex
1846 : Neptune predicted and discovered
Celestial mechanics flourishes
AltAlt-azimuth circle 1789 for
Piazzi’s Palermo Observatory
1860 - : Bonner + Cordoba Surveys 1,000,000 stars
1890 - : Photography : parallaxes and sky surveys
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Astrometry of small angles 1/2
Astrometry of small angles 2/2
i.e. within the telescope field of view
i.e. within the telescope field of view
1611 – 1660 : Estimation: diameters, relative positions,
Galilei et al.
1659 – 1990 : Wire micrometer by Huygens
Gascoigne 1640, published later
B
A
From 1750 also heliometer =
. C
.
divided--lens micrometer
divided
A
for the same purposes
.
Science :
..
Diameters of planets
Relative positions
Double stars : stellar masses
Relative parallaxes 18381838-1900
1890 - 1990 : Photography : same science as micrometer :
Diameters of planets
Relative positions of stars and solar system objects
Double stars : stellar masses
Relative parallaxes
1990 - : 1,000,000,000 stars, e.g. US Naval Observatory Catalogues
1920 - : Interferometry : stellar diameters, double stars
1990 - : Space astrometry : Hipparcos, Hubble
1980 - : CCD astrometry :
on ground : 100,000,000 stars to 17th mag + solar system
from space : Hubble relative parallaxes 0.001”
Principle of the
wire micrometer
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Some results from astrometry 19001900-2000
By 1900 : 539 stars 0.01”/a motions Decl. > -10 deg
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Copenhagen meridian circle
Photoelectric astrometry begins in 1925
1905 : Hertzsprung discovers dwarfs/giants using motions for distances
100 stars 0.04” relative parallaxes
By 1950 : 33,342 stars 0.01”/a motions,
5822 stars 0.01” relative parallaxes
500 stars with <10% error on distances
1970 - : Radio astrometry : accurate absolute positions,
reference system by quasars, Earth rotation
1996 : Hipparcos satellite : accurate large & small angles
120,000 stars 0.001”/a motions (N & S)
120,000 stars 0.001” absolute parallaxes
22,000 stars with <10% error on distances
2000 : Tycho
Tycho--2 : 2.500,000 stars 0.002”/a motions
USNO : 1,000,000,000 stars to 20th mag
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Courtesy: Steno Museum, Aarhus
Bengt Strömgren 1925 and 1933
Experiments with
photoelectric recording of transits
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Slits + Photon counting vs. Time
=> Astrometry + Photometry
Carlsberg automatic meridian circle
on La Palma from 1984
Ideas 1960
y
y
t2
t1
Photoelectric
during 14 years
star
x1
x2
x
Light intensity
= Photons
per second
x ~ time
t1
t2
Then from 1998
CCD micrometer :
20,000,000 star
observations
per year
0.1” per obs.
time
+ switching
mirror mirror
B. Strömgren 1933: slits
+ switching
Atomic bombs 1957 : Counting techniques
E. Høg 1960 : Slits + counting >>> implementation on meridian circles
P. Lacroute 1967: Go to space!
E. Høg 1975: Design of Hipparcos
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Telescope of Hipparcos
Hipparcos and Tycho 19751975-2000
Focal plane of Hipparcos –
Tycho
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Star mapper
grid
Mission concept 1975
Mission approval Feb. 1980
Tycho proposal April 1981
Observing 1989 - 93
Catalogues 1996
Tycho--2 Catalogue in 2000
Tycho
2.500,000 stars
500 citations until 2008
Schmidt type
system
D = 0.29 m
F = 1.4 m
Two fields on the sky
Modulating grid
Observing 1989 - 93
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Telescope and payload of Gaia
Astrometric Accuracy versus Time
Launch 2012
Two SiC primary mirrors
Rotation axis (6 h)
1.45 × 0.50 m2 at 106.5°
106.5°
Basic angle
monitoring system
Hipparchus/Ptolemy - 1000 stars
1000
T he Landgrave of Hesse - 1000 stars
100
SiC toroidal
structure
(optical bench)
Tycho Brahe - 1000
Flamsteed - 3000
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Lalande - 50,000
arcsec 1
Bradley - aberration
0.1
0.01
0.001
Superposition of
two Fields of View
Combined
focal plane
(CCDs)
F = 35 m
0.0001
0.00001
Erik Høg
1995/2008
Argelander - 34,000
FK5 - 1500
Bessel - 1 star
Jenkins - 6000
Positions
Parallaxes =
Small angles
Hipparcos - 120,000
ROEMER - 4 5 million
Proposal 1992
All parameters
PPM - 379,000
TychoTycho-2
- 2.5 million
U SNO - 360
Gaia
- 1200 million
Gaia 23 million
SIM - 10,000
150 BC … 1600
1800
2000
Year
Two anastigmatic offoff-axis telescopes
Figure courtesy EADSEADS-Astrium
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