THE LHIRES-III SPECTROGRAPH © C2PU, Observatoire de la Cote d’Azur, Université de Nice Sophia-Antipolis Jean-Pierre Rivet CNRS, OCA, Dept. Lagrange

The LHIRES-III 05/09/2015C2PU-Team, Observatoire de Nice2 LHIRES = Littrow High RESolution spectrograph

Diffraction by 1 element 05/09/2015C2PU-Team, Observatoire de Nice3 Incident beam assumed parallel (wavelength  ) Diffracted beam Collimator Screen ~ / d d Non-reflecting substrate Maximum in the direction of geometric optics:  r = -  r Angular width: ~ / d ii rr Reflecting element

Diffraction by “n” elements 05/09/2015C2PU-Team, Observatoire de Nice 4 Incident beam (wavelength  ) Screen ? Non-reflecting substrate Reflecting elements Collimator ii

Diffraction by “n” elements 05/09/2015C2PU-Team, Observatoire de Nice5 Incident beam (wavelength  ) ii Screen ? Collimator 

Diffraction by “n” elements 05/09/2015C2PU-Team, Observatoire de Nice6 Screen Collimator NO LIGHT ! Diffracted beams out of phase : destructive interferences  NO LIGHT

Diffraction by “n” elements 05/09/2015C2PU-Team, Observatoire de Nice7 Screen Collimator LIGHT ! Diffracted beams in phase : constructive interferences  MAXIMUM LIGHT

Diffraction by “n” elements 05/09/2015C2PU-Team, Observatoire de Nice8 aaaa ii Ray 0 Ray 1 Delay of Ray 1 wrt Ray 0 = a sin(  i )

Diffraction by “n” elements 05/09/2015C2PU-Team, Observatoire de Nice9 aaaa rr Ray 0 Ray 1 Delay of Ray 1 wrt Ray 0 = a sin(  r )

Diffraction by “n” elements 05/09/2015C2PU-Team, Observatoire de Nice10 aaaa rr Ray 0 Ray 1 ii Ray 0 Ray 1 Total delay of Ray 1 wrt Ray 0 :  = a sin(  i ) + a sin(  r ) Condition for constructive interferences:  = k. integer; called the “order”

Diffraction by “n” elements 05/09/2015C2PU-Team, Observatoire de Nice11 aaaa rr Ray 0 ’ Ray 1 ’ ii Ray 0 Ray 1 Order k = 0 Condition for constructive interferences:  = 0, whatever sin(  i ) + sin(  r ) = 0 Snell’s law ! direction of reflection on the grating’s plane according to geometric optics NON DISPERSIVE

Diffraction by “n” elements 05/09/2015C2PU-Team, Observatoire de Nice12 aaaa rr Ray 0 ’ Ray 1 ’ ii Ray 0 Ray 1 Order k ≠ 0 Condition for constructive interferences:  = k. sin(  i ) + sin(  r ) = k. / a DISPERSIVE

Diffraction pattern (monochr.) 05/09/2015C2PU-Team, Observatoire de Nice13 sin(  i ) + sin(  r ) 0 Relative intensity aaaa N d ~ / ( N.a ) ~ / a ~ / d Diffraction enveloppe / a 2 / a 3 / a - / a -2 / a -3 / a

Diffraction pattern (polychr.) 05/09/2015C2PU-Team, Observatoire de Nice14 sin(  i ) + sin(  r ) 0 Relative intensity / a 2 / a 3 / a - / a -2 / a -3 / a Order 0: non dispersive Order 1: dispersive Order 2: more dispersive Order 3: even more dispersive

Blazed gratings 05/09/2015C2PU-Team, Observatoire de Nice 15 rr ii Diffraction envelope is maximum when:  r = -  i 0 th order is maximum when:  r = -  i rr ii Diffraction envelope is maximum when:  r = -  i 0 th order is maximum when:  r = -  i : Normal to the grating : Normal to the grooves rr  (blaze angle) ii STANDARD GRATING BLAZED GRATING

Diffraction pattern 05/09/2015C2PU-Team, Observatoire de Nice16 sin(  i ) + sin(  r ) 0 Relative intensity / a 2 / a 3 / a - / a -2 / a -3 / a Order 0: non dispersive Order 1: dispersive Order 2: more dispersive Order 3: even more dispersive STANDARD GRATING

Diffraction pattern 05/09/2015C2PU-Team, Observatoire de Nice17 sin(  i ) + sin(  r ) 0 Relative intensity / a 2 / a 3 / a - / a -2 / a -3 / a Maximum of diffraction curve on order k ≠ 0 BLAZED GRATING Blaze angle  depends on the central wavelength 0 and order k

Basics on spectrographs 05/09/2015C2PU-Team, Observatoire de Nice18 Dispersing element (grating) rr ii Collimated input beam Collimation optics Dispersed beam Camera optics Sensor Entrance slit Light from the telescope

Littrow configuration 05/09/2015C2PU-Team, Observatoire de Nice19 ii Littrow condition:  r =  i  Collimator optics = Camera optics (cost effective configuration) rr

The LHIRES-III 05/09/2015C2PU-Team, Observatoire de Nice20

The LHIRES-III 05/09/2015C2PU-Team, Observatoire de Nice21 Micrometric screw (to tilt the gating) Diffraction blazed grating) Collimator / camera optics Bending mirror Science camera Guiding camera Focuser for the guiding camera Slit environment Bending mirror F/12.5 input beam from the telescope

The LHIRES-III 05/09/2015C2PU-Team, Observatoire de Nice22 Micrometric screw (to tilt the gating) Diffraction blazed grating) Collimator / camera optics Bending mirror Science port Guiding port Focuser for the guiding camera Slit environment Bending mirror F/12.5 input port

The LHIRES-III 05/09/2015C2PU-Team, Observatoire de Nice23

The slit environment 05/09/2015C2PU-Team, Observatoire de Nice24 Bending flat mirror Input beam (from telescope) Guiding output port Input slit Output port focusing optics Slit environment

The slit environment 05/09/2015C2PU-Team, Observatoire de Nice25 15  m slit 19  m slit Active slit 25  m slit 35  m slit Optically polished component: MUST HE HANDELED WITH CARE

The calibration lamp 05/09/2015C2PU-Team, Observatoire de Nice26 Calibration lamp housing Calibration lamp flip button

The Neon spectrum 05/09/2015C2PU-Team, Observatoire de Nice27

The diffraction ratings 05/09/2015C2PU-Team, Observatoire de Nice28 Protection frame Active grating surface Housing Tilt axis High precision optical component: MUST HE HANDELED WITH EXTREME CARE NO FINGER PRINTS ! Available gratings: 150 gr/mm 300 gr/mm 2400 gr/mm

The micrometric screw 05/09/2015C2PU-Team, Observatoire de Nice29 Fixed tilt axis Active grating surface Last visible mark: 23.5 Drum tick mark in front of the fixed index : 34 How to read the micrometric screw : Fixed index Value = = Micrometric screw Half-integer tick marks Integer tick marks

Configurations 05/09/2015C2PU-Team, Observatoire de Nice30 Available slits: 15 microns 19 microns 23 microns 35 microns 15  m19  m23  m35  m 150 gr/mm gr/mm gr/mm Slit Grating Spectral 589nm Available gratings: 150 gr/mm 300 gr/mm 2400 gr/mm

Sample spectra 05/09/ The Hydrogen H  line in the solar spectrum (LHIRES-III gr/mm)

Sample spectra 05/09/ The Sodium D1 and D2 lines in the solar spectrum (LHIRES-III gr/mm)

Sample spectra 05/09/ The Magnesium triplet in the solar spectrum (LHIRES-III gr/mm)

Sample spectra 05/09/ The Hydrogen H  line in Saturn’s spectrum (LHIRES-III gr/mm) The lines are tilted by the planet’s surface rotation (Doppler effect)