1. C2PU TELESCOPES Version 02, 28/08/2016 Jean-Pierre Rivet CNRS, OCA,
Dept. Lagrange
© C2PU, Observatoire de la Cote d’Azur,
Université de Nice Sophia-Antipolis

2. C2PU-Team, Observatoire de Nice
C2PU: two telescopes
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”)
18/11/2018
C2PU-Team, Observatoire de Nice

3. C2PU Telescopes : optical combinations
Cassegrain secondary focus
Secondary mirror
(hyperbolic)
Magnifies a lot
Narrow field of view
Best for planetary imaging
F mm
D = 1040 mm
F / D = 12.5
AVAILABLE
ON BOTH
TELESCOPES !
Primary mirror
(parabolic)
CCD camera
at secondary focus
18/11/2018
C2PU-Team, Observatoire de Nice

4. C2PU Telescopes : optical combinations
Pure primary focus configuration
Simple, perfect at center,
BUT strong coma
aberration off-axis !
CCD camera
at primary focus
F mm
D = 1040 mm
F / D = 2.88
Primary mirror
(parabolic)
18/11/2018
C2PU-Team, Observatoire de Nice

5. C2PU Telescope : optical combinations
Prime focus configuration with Wynne corrector
CCD camera
at corrected primary focus
Much better !
3-lens Wynne
coma corrector
F mm
D = 1040 mm
F / D = 3.17
Primary mirror
(parabolic)
18/11/2018
C2PU-Team, Observatoire de Nice

6. How focalization is done
Prime focus configuration with Wynne corrector
All the focal assembly
(Wynne corrector + Camera)
can move up and down.
Fully motorized, computer-operated,
with position gauge
Focalization
AVAILABLE
ON OMICRON
TELESCOPE ONLY !
18/11/2018
C2PU-Team, Observatoire de Nice

7. Sample image Galaxy NGC 6946: Distance:  10 Mly App. size: 9.8  11 ‘
Telescope:
Focus: Primary + ParraCor
Camera: SBIG ST4000 XCM
Exposure: 90 x 2mn
Date: 14/09/2012
Author: David Vernet
18/11/2018

8. C2PU Telescopes : optical combinations
Celestial North pole
“Coudé” focus
4th mirror
(flat)
Secondary mirror
(hyperbolic)
Polar axis
CCD camera
at coudé focus
Magnifies a lot
Very narrow field of view
Fixed focus
Best for “big” focal sensors
3rd mirror
(flat)
Optical bench
AVAILABLE
ON EPSILON
TELESCOPE ONLY !
F = mm
D = 1040 mm
F / D = 35
5th mirror
(flat)
Primary mirror
(parabolic)
18/11/2018
C2PU-Team, Observatoire de Nice

9. Optical configurations
Prime focus +
Wynne corrector
F/3.2:
Photometry,
Astrometry,
Occultations.
Wide field imaging.
Coudé focus F/35
Only for invited
instruments
West dome
Omicron telescope
East dome
Epsilon telescope
Cassegrain focus
F/12.5 or F/9.0
(with focal reducer):
Spectroscopy,
Narrow field imaging.
Cassegrain focus
F/12.5 or F/9.0
(with focal reducer)
Spectroscopy,
Narrow field imaging.
18/11/2018
C2PU-Team, Observatoire de Nice

10. Equatorial mount Eppur si muove ! Earth is in rotation,
North
polar axis
Eppur si muove !
(Galileo Galilei, 1633)
Earth is in rotation,
but stars are “fixed” !
So, you need an
Equatorial mount...
Earth’s rotation
Equatorial plane
18/11/2018

11. Equatorial mount If my observatory was at North Pole.. This is an
polar axis
If my observatory
was at North Pole..
 to equatorial plane
Observatory
Earth’s rotation could be
compensated easily, by
an opposite rotation
of the telescope’s mount
Telescope’s rotation
Local
meridian
Earth’s rotation
This is an
Equatorial mount..
Equatorial plane
18/11/2018

12. Equatorial mount If my observatory is NOT at North Pole.. This is an
polar
axis
// to North
polar
axis
If my observatory
is NOT at North Pole..
 to equatorial plane
Earth’s rotation can be
compensated as well, by
an opposite rotation
of the telescope’s mount
Observatory
Local
meridian
This is an
Equatorial mount..
Equatorial plane
18/11/2018

13. Equatorial mount Equatorial mount: the North polar axis of the mount
Local
meridian
 to equatorial plane
// to North polar axis
Observatory
Zenith
Equatorial plane
Latitude
Horizontal plane
Equatorial mount:
the North polar axis of the mount
is tilted on the horizon, of an
angle equal to the local latitude
18/11/2018

14. Equatorial mount Equatorial mount: the North polar axis of the mount
Local
meridian
 to equatorial plane
// to North polar axis
Observatory
Zenith
Equatorial plane
Latitude
Horizontal plane
Equatorial mount:
the North polar axis of the mount
is tilted on the horizon, of an
angle equal to the local latitude
18/11/2018

15. C2PU-Team, Observatoire de Nice
Mount coordinates
Origin: mount axes intersection
(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
North pole r  O H
These are the natural coordinates
for a telescope equatorial mount,
delivered by its angular encoders !!!
Equatorial plane
local meridian
Beware !
H angle defined from star meridian to local meridian !
18/11/2018
C2PU-Team, Observatoire de Nice

16. Mount coordinates and equatorial mount
North polar axis r
Declination
axis  H O
Hour angle
axis H
Telescope
equatorial
mount
Equatorial plane
Mount coordinates
local meridian
18/11/2018
C2PU-Team, Observatoire de Nice

17. C2PU Telescopes : equatorial yoke mount
Yoke mount “pros and cons” :
Very stable mechanically
Low flexion
Limitations in accessible
sky zone (blind angles).
... More on that later.
Polar axis H 
North pillar
Telescope’s tube
(Serrurier structure)
Yoke
Declination axis
South pillar
18/11/2018
C2PU-Team, Observatoire de Nice

18. Omicron Telescope : accessible zone
Elevation:
h > 18°
Declination:
< 60°
Hour angle:
-6h < H < +6h
18/11/2018
C2PU-Team, Observatoire de Nice

19. Epsilon Telescope : accessible zone
Elevation:
h > 21°
Declination:
< 60°
Hour angle:
-5.3h < H < +5.3h
18/11/2018
C2PU-Team, Observatoire de Nice

20. C2PU-Team, Observatoire de Nice
ENJOY !
18/11/2018
C2PU-Team, Observatoire de Nice