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

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

C2PU Telescopes : optical combinations Cassegrain secondary focus Secondary mirror (hyperbolic) Magnifies a lot Narrow field of view Best for planetary imaging F 13000 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

C2PU Telescopes : optical combinations Pure primary focus configuration Simple, perfect at center, BUT strong coma aberration off-axis ! CCD camera at primary focus F 2995 mm D = 1040 mm F / D = 2.88 Primary mirror (parabolic) 18/11/2018 C2PU-Team, Observatoire de Nice

C2PU Telescope : optical combinations Prime focus configuration with Wynne corrector CCD camera at corrected primary focus Much better ! 3-lens Wynne coma corrector F 3297 mm D = 1040 mm F / D = 3.17 Primary mirror (parabolic) 18/11/2018 C2PU-Team, Observatoire de Nice

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

Sample image Galaxy NGC 6946: Distance:  10 Mly App. size: 9.8  11 ‘ Telescope: omicron@C2PU Focus: Primary + ParraCor Camera: SBIG ST4000 XCM Exposure: 90 x 2mn Date: 14/09/2012 Author: David Vernet 18/11/2018

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 = 36400 mm D = 1040 mm F / D = 35 5th mirror (flat) Primary mirror (parabolic) 18/11/2018 C2PU-Team, Observatoire de Nice

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

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

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

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

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

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

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

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

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

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

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

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