astronomy instrumentation
DESCRIPTION
Astronomy Summer School for West Africa. Astronomy Instrumentation. Daniel Okoh. Outline:. Telescopes. Telescopes. Telescopes. Astronomy Instrumentation. Telescopes: What are they?. They are instruments that enable us ‘see’ distant objects by gathering ‘light’ from them. - PowerPoint PPT PresentationTRANSCRIPT
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Astronomy Instrumentation
Astronomy Summer School for West Africa
Daniel Okoh
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Astronomy Instrumentation
Outline:Telescopes
Telescopes
Telescopes
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Astronomy Instrumentation
Telescopes: What are they?They are instruments that enable us ‘see’ distant objects by gathering ‘light’ from them
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Astronomy Instrumentation
Telescopes: What are they?
Optical Telescopes Radio Telescopes
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Astronomy Instrumentation
Optical Telescopes
They come in various sizes
and form
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Astronomy Instrumentation
Optical Telescopes: Basic Operation
ObjectiveEye piece
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Astronomy Instrumentation
Optical Telescopes: Basic Operation
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Astronomy Instrumentation
Radio Telescopes
They need to be big! Really really big!!
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Astronomy Instrumentation
Why?The Quest for more!
Oliver Twist
θ =
λD
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Astronomy Instrumentation
Telescopes in Space
Windows and Walls
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Astronomy InstrumentationTelescopes in Space
Hubble Space Telescope
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Astronomy Instrumentation
Angular sizes in astronomy
θ
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Astronomy Instrumentation
If the same object is farther away, the angular size is
smaller
θ1
θ2
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Astronomy Instrumentation
Objects of different linear sizes can have the same
angular sizes
θ
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Astronomy Instrumentation
Activity 1: Estimate the angular size of your full fist at
arm’s length
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Astronomy Instrumentation
Activity 1: Estimate the angular size of your full fist at
arm’s length
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Astronomy Instrumentation
Activity 1: Estimate the angular size of your full fist at
arm’s length
θθ y
x
x
tan θ = x/y
2θ = 2 tan-1 (x/y)
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Astronomy Instrumentation
Activity 1: Estimate the angular size of your full fist at
arm’s length
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Astronomy Instrumentation
Small angle approximation
Ad
DA = D/d * 57.3 degrees
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Astronomy Instrumentation
Activity 2: Angular size of the Sun
A
1.4*106
kmA = ??
1.5*108 km
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Astronomy Instrumentation
Activity 2: Angular size of the Moon
A
3,475 km
A = ??
384,400 km
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Astronomy Instrumentation
0.5 degrees! for both Sun and Moon
Sun and Moon same size?
Eclipse Implication?
Fist or finger to block out the Moon?
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Astronomy Instrumentation
Telescope Resolutions
2 degrees!?
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Astronomy Instrumentation
Why Radio Telescopes should be larger than optical
telescopes
θ =
λD
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Astronomy Instrumentation
Activity 3: What Radio = Optical telescope ?
A 25 cm Optical Telescope will have same resolution as a …… cm Radio
TelescopeAssume Optical Telescope λ = 500 nm
And Radio Telescope λ = 6 cm
30 km ??
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Astronomy Instrumentation
VLBI (Very Long Baseline Interferometry)
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Astronomy Instrumentation
Radio Antenna Surfaces
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Astronomy Instrumentation
Radio Antenna Surfaces
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Astronomy Instrumentation
Steering in Azimuth And
Elevation
Where we have to look to see stars and other
objects
A. 0B. 10C. 45D. 90
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Astronomy Instrumentation
Steering in Azimuth And Elevation A. 0
B. 10C. 45D. 90
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Astronomy Instrumentation
Radio Telescope Receivers Similar in many ways to other receivers we
use for TV and other radio collectionsMajor difference:
Astronomy signals are really very weak compared to other terrestrial signals
What constitutes noise is therefore highSignal to noise ratios can be reduced
by reducing receiver temperaturesThere is need to cool the receivers to
really low temperatures
God Dependent
Cryogenic
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Astronomy Instrumentation
The Address of stars:
Right Ascension
Declination
Room 105Department of Physics &
AstronomyUniversity of Nigeria
NsukkaEnugu State
Nigeria
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Celestial Equator
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Astronomy Instrumentation
Activity 4: Telescope PointingDetermine the direction (azimuth and elevation) a telescope
should point this evening at 6:34 PM to be able to observe α – Centauri from here in Abuja.
Assume 2 telescopes at Nsukka and Abuja are to be used for VLBI observations of Sirius at 8:22 AM tomorrow morning. At what directions should each of the telescopes point?
Will it be possible to join a telescope at Nanshan, China to this VLBI observation? What about a telescope at Cape Town, South Africa?