C2PU TELESCOPESC2PU TELESCOPES

© C2PU, Observatoire de la Cote d’Azur,

Université de Nice Sophia-Antipolis

Jean-Pierre RivetCNRS, OCA,Dept. Lagrangejean-pierre.rivet@oca.eu

Version 02, 01/09/2015

C2PU: two telescopes

21/04/23 C2PU-Team, Observatoire de Nice 2

West dome

East dome

West (“Ouest” in French): omicron telescope (“omicron”: Greek leter for “O”)East (“Est” in French): epsilon telescope (“epsilon”: Greek letter for “E”)

epsilon@C2PU: ready for use; access restrictedomicron@C2PU: ready for use

C2PU Telescopes :optical combinations

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Cassegrain secondary focus

Primary mirror

(parabolic)

Secondary mirror

(hyperbolic)

F 13000 mmD = 1040 mmF / D = 12.5

• Magnifies a lot• Narrow field of view• Best for planetary imaging

CCD camera

at secondary focus

AVAILABLE

ON BOTH

TELESCOPES !

C2PU Telescopes :optical combinations

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Pure primary focus configuration

Primary mirror

(parabolic)

CCD camera

at primary focus

F 2995 mmD = 1040 mmF / D = 2.88

Simple, perfect at center,BUT strong coma aberration off-axis !

C2PU Telescope :optical combinations

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Prime focus configuration with Wynne corrector

Primary mirror

(parabolic)

CCD camera

at corrected primary focus

F 3297 mmD = 1040 mmF / D = 3.17

Much better !3-lens Wynne

coma corrector

How focalization is done

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Prime focus configuration with Wynne corrector

Focalization

All the focal assembly (Wynne corrector + Camera)can move up and down.Fully motorized, computer-operated,with position gauge

AVAILABLE

ON OMICRON

TELESCOPE ONLY !

Sample image

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Galaxy NGC 6946:Distance: 10 MlyApp. size: 9.8 11 ‘

Telescope: omicron@C2PUFocus: Primary + ParraCorCamera: SBIG ST4000 XCMExposure: 90 x 2mnDate: 14/09/2012Author: David Vernet

C2PU Telescopes :optical combinations

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“Coudé” focus

Primary mirror

(parabolic)

Secondary mirror

(hyperbolic)

F = 36400 mmD = 1040 mmF / D = 12.5

• Magnifies a lot• Very narrow field of view• Fixed focus• Best for “big” focal sensors

CCD camera

at coudé focus

AVAILABLE

ON EPSILON

TELESCOPE ONLY !

Optical bench

Celestial North pole

Polar axis

3rd mirror

(flat)

4th mirror

(flat)

5th mirror

(flat)

Optical configurations

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West domeOmicron telescope East dome

Epsilon telescope

Cassegrain focus

F/12.5 or F/9.0

(with focal reducer)

Prime focus +

Wynne corrector

F/3.2

Cassegrain focus

F/12.5 or F/9.0

(with focal reducer)

Coudé focus F/35

(in progress)

Mount coordinates

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Equatorial plane

Nor

th p

ole

Sun

loca

l mer

idia

n

H

• Origin: observatory position (topocentric).• Fundamental plane: Equatorial plane• Polar axis: Geographic North pole• Zero direction: Local meridian• H : hour angle (in hours !)• : declination (in degrees)• r : topocentric distance

These are the natural coordinatesfor a telescope equatorial mount,delivered by its angular encoders !!!

r

Beware !H angle defined from star meridian to local meridian !

Mount coordinatesand equatorial mount

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Equatorial plane

Nor

th p

olar

axi

s

Sun

loca

l mer

idia

n

H

r

Hour angleaxis

Declination

axis

H

Mount coordinates

Telescopeequatorial

mount

Equatorial mount

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Equ

ator

ial p

lane

Earth’s rotation

Earth is in rotation,

but stars are “fixed” !

So, you need an Equatorial mount...

Eppur si muove ! (Galileo Galilei, 1633)

Northpolar axis

Equatorial mount

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Northpolar axis

Local meridian

to

equ

ator

ial p

lane

Equ

ator

ial p

lane

If my observatorywas at North Pole..

Earth’s rotation

Observatory

Telescope’s rotationEarth’s rotation could becompensated easily, by an opposite rotationof the telescope’s mount

This is an Equatorial mount..

Equatorial mount

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Northpolaraxis

Local meridian

to

equ

ator

ial p

lane

Equ

ator

ial p

lane

// to Northpolaraxis

Observatory

If my observatoryis NOT at North Pole..

Earth’s rotation can becompensated as well, by an opposite rotationof the telescope’s mount

This is an Equatorial mount..

Equatorial mount

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Northpolaraxis

Local meridian

to equatorial plane

// to North polar axis

Observatory

Zenith

Equatorial plane

Latitude

Horizontal plane

Latitude

Equatorial mount:the North polar axis of the mountis tilted on the horizon, of anangle equal to the local latitude

Equatorial mount

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North

pola

rax

is

Loca

l m

erid

ian

to

equ

ator

ial p

lane

// to

Nor

th p

olar

axis

Obs

erva

tory

Zen

ith

Equat

oria

l pla

ne

Latitude

Horizontal planeLatit

ude

Equatorial mount:the North polar axis of the mountis tilted on the horizon, of anangle equal to the local latitude

C2PU Telescopes :equatorial yoke mount

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South pillar

North pillar

Yoke

Polar axis

Declin

atio

n ax

is

H

Telescope’s tube

(Serrurier structure)

Yoke mount “pros and cons” :•Very stable mechanically•Low flexion•Limitations in accessible sky zone (blind angles). ... More on that later.

Omicron Telescope :accessible zone

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Elevation:h > 18°

Declination:< 60°

Hour angle:-6h < H < +6h

Omicron Telescope :accessible zone

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Elevation:h > 18°

Declination:< 60°

Hour angle:-6h < H < +6h

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ENJOY !