TWIN BOOK PROJECT door Marc Trypsteen


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4. Complete Spectroscopy for Amateur Astronomers COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

29. Phase 1: Interested amateurs An Important message to all interested amateurs that must be clear at the very beginning is that a Pro - Am collaboration is a high quality science project. The primary goal of this collaboration is to make a contribution to scientific work which can be a (funded) local or cross - border project. Sometimes it can also be organized as a contribution to a PHD or postdoctoral teamwork. The first task for the Pro - Am coordinator is to thoroughly inform interested amateurs about the philosophy of the Pro - Am collaboration to avoid overall deception afterwards. COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

33. Ancient cultures looked up to the stars, telling each other myths and legends : beautiful starlores . The moral of those tales , over the years survived for mankind . Modern cultures look to the stars too : the era of the high tech eyes explores the universe in another way and will help mankind to survive Enjoy the fascinating world of astronomical spectroscopy Marc Trypsteen

21. ALL - IN - ONE ILLUSTRATIONS RESULTING IN: - Better insight - Direct comparison - Instant overview of different possibilities COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN



7. TABLE OF CONTENTS SPECTRAL ATLAS 1. Directory of plates 2. Selection, processing and presentation of the spectra 3. Terms, definitions and abbreviations 4. Overview and characteristics of stellar spectral classes 5. Spectral class O 6. Spectral class B 7. Spectral class A 8. Spectral class F 9. Spectral class G 10. Spectral class K 11. Spectral class M 12. Spectral sequence on the AGB 13. M(e) stars on the AGB 14. Spectral class S on the AGB 15. Carbon stars on the AGB 16. Post AGB stars and white dwarf 17. Wolf Rayet stars 18. LBV stars 19. Be stars 20. Be shell stars 21. PMS protostars 22. Peculiar CP - stars 23. Spectroscopic binaries 24. Novae 25. Supernovae 26. Extragalactic objects 27. Star clusters 28. Emission nebulae 29. Reflectance spectra of solar system bodies 30. Telluric molecular absorption 31. The night sky spectrum 32. Terrestrial and calibration light sources. The spectral atlas covers a broad range of astronomical objects and interesting light sources COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

25. Echelle R ≈ 20,000 Magnesium Triplet: λ 5167, 5173, 5183 DADOS R ≈ 4000 (900L/mm) DADOS R ≈ 800 (200L/mm) Influence of the Spectrograph Resolution on the FWHM - and EW Values The spectral profiles of the Sun in Fig. 9.7, recorded with differently high resolutions show the influence on the recorded spectral lines. The R - values are here within a range of approximately 800 – 20,000. Influence of the spectral resolution on the recorded spectral lines ( Huwiler / Walker) COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

11. WILSON – BAPPAU EFFECT H K α Boo Sun Detailed visualisation of specific effects observed in recorded higher resolution spectra COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN


14. PLATE 69 Saturn Nebula NGC 7009 Classification lines He II 4685.7 H β 4861.33 [O lll ] 4958.91 [O lll ] 5006.84 H γ 4340.5 H δ 4101.74 He I 5875.6 H α 6562.82 [N ll ] 6583.6 [Ne III] 3868.76 [Ne III] 3967.47 [Ar IV] 4740.3 He I 4471.5 [Ar IV] 4711.34 [O III] 4363.2 [N III] 4641 Criterion log (I N1+N2 / I He II (4686) )≈ 1.9  Excitation class E8 Zoom in the Intensity axis Original Profile COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

26. Wilson - Bappu Effect A possible way to use also giants from the spectral classes G – M for the spectroscopic distance estimation is to apply the Wilson - Bappu effect. Already 1957 O. Wilson and K. Bappu discovered a remarkable correlation between the measured width of the small emission in the core of the Ca II K - line ( λ 3933.66) and the absolute visual magnitude of Giants. For amateurs with high resolution spectrographs (R ~ 20'000) this is an interesting field for experiments. Fig. 10.9 shows a strong zoom on the according emission core of Arcturus, fully displayed in the spectral atlas [1]. It shows how the width Δ λ is measured, i.e. on each side of the line at half intensity between K1 and K2. Here follows, in a long sequence since the 1960ies, the most recent calibration [128] of this empirical law: Mv =33.2 - 18∙log W0 10.1 where W0= Δλ /λ0∙c Ca II K - line is preferred for this analysis because it has been revealed that in high resolution spectroscopy the Ca II H - line is often contaminated by other adjacent lines. 3933 3934 K1b K2b K1r K2r Δ λ Synchronised with the Spectral Atlas, Volume 2 focuses in detail on the theory behind the observed effects and their useful practical applications COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

19. 3646 Å 3.40 eV Balmer Edge 6563 Å 4861 Å 4340 Å 4102 Å 3970 Å 3889 Å H β H γ H δ H ε H ζ H α n = 2 n = 3 n = 4 n = 5 n = 6 n = 7 1.89 eV 2.55 eV 3.02 eV 2.86 eV 3.12 eV 3.19 eV Photon Energy E [eV] Electron Transition n = ∞ Wavelength Direct visualisation of the link between the recorded spectrum and the electron transitions responsible for the generation of the spectrum COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

6.  Acknowledgements  The spectral atlas was launched in 2011 as a nonprofit project. The aim was first to provide an internet document with fully commented, low resolution spectra for amateurs, covering the seven basic spectral classes. At that time, this way also a significant publication gap should be reduced. Anyway first thanks deserve here Urs Flükiger , member of the Swiss Spectroscopic Group, convincing the author to publish the very first version of the atlas on his " Ursus Maior " homepage. Otherwise it could even be possible that the manuscript would still remain as "personal notes" in any folder on his Laptop.  The following worldwide responses to the very first online version have been surprisingly numerous and so positive that the project was soon extended to further special classes. Thus further thanks are here addressed to all amateurs and even professionals, which have contributed with their valuable feed backs to the benefit of this atlas.  Already 2011 Thomas Eversberg from DLR wrote a review in the VDS Journal Nr . 38 and was also the very first to propose, that this atlas should be published as a book. Anyway further five years have been required to record the spectra for all presently documented special classes and to collect the necessary background information for the description of the numerous objects. At this stage I got valuable support also by Martin Huwiler which assisted me with his immense optical knowledge, but also by discussing relevant spectroscopic and astronomical topics as well as by reviewing the text. In this respect I would like to include also Helen Wider. Further Erik Wischnewski helped me with the chapter about Novae and contributed excellent, self recorded spectra of Nova Delphini V339, which annoyingly erupted exactly during a time when the author was prevented from observing.  2014, during the NEAF convention near New York, Olivier Thizy of Shelyak Instruments met Vince Higgs from CUP and called his attention to the atlas project, which however was not yet finished at that time and required a further year to be completed. So Olivier made this way a small but nevertheless decisive contribution to the creation of this book. Further the excellent programs Visual Spec by Valerie Désnoux and IRIS by Christian Buil have been of great help, not only for analyzing of the recorded profiles but also for the illustration of the numerous colored plates in this atlas.  While transferring the internet document into a book it became clear quite soon, that a separate publication would be necessary, supporting the atlas with practical and theoretical aspects. Anyway this required inevitably a co - author with complementary knowledge, for which fortunately Marc Trypsteen could be won. He contributed also valuable reviews and inputs to the atlas, not least a stunning reflectance - spectrum of the lunar eclipse from September 2015.  Finally I generally want to express here again my warmest thanks to everyone who contributed in any kind to this atlas.  Richard Walker  COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

20. Dispersion By Refraction By Diffraction Bending Blue side > Red side Red side > Blue side Causing Mechanism Push/Pull on electrons Absorption/Re - emission λ versus slit opening Dimension difference Examples Rainbow, Prism spectrographs Transmission - /Reflective grating spectrographs Clear overviews by tables for a quick insight and memorization COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

17.  Acknowledgements  While working for the Spectral atlas quite soon the necessity for a separate book became obvious, which would relieve the atlas from theoretical and practical matters. This way the amateur astronomer has at his disposal a second book, which provides supplementary information and interesting astrophysical applications, customized to his specific needs. Parallel to the atlas it fills the gap between theoretical knowledge and practical astronomical spectroscopy, simultaneously opening the way to a more professional approach, a “ conditio sine qua non” for a successful participation in Pro - Am spectroscopy projects. For this multidisciplinary task we wish to thank all people involved for their valuable advices and cooperation. The numerous e - mails between us and colleagues, amateurs, professionals, companies and friends have been a tremendous help for the fine - tuning of this work. Therefore the many persons, already involved and mentioned in this context with respect to the realization of the spectral atlas, deserve here our acknowledgement. Anyway we hope for understanding if not all are here mentioned individually again.  Special thanks go to the company representatives or manufacturers of astronomical spectrographs, being : Johannes & Thomas Baader ( Baader Planetarium, Germany), Martin Huwiler (Eagle Owl Optics, Switzerland), Terry Platt (Starlight Xpress, UK), Daniel Sablowski Astro Spectroscopy Instruments, Germany), Olivier Thizy ( Shelyak , France), Mark Woodward & Ken Harrison (JTW astronomy, The Netherlands) for their willingness to provide detailed technical information and illustrations on their spectrographs. We are also grateful for their continuous efforts to offer entry level and research grade spectrographs for personal, educational and scientific cooperative projects. Additionally a special recognition is headed here to Martin Huwiler , who substantially contributed to chapters, containing optical and/or practical aspects.  An especially high effort required the search for information about the calibration of the spectral flux density, revealing here a lack of appropriate publications, treating this topic not just fragmentary but rather comprehensively. To provide here a somewhat reasonable overview, tailored to the needs of the amateur, the information had tediously to be gathered from numerous sources. In addition further supplementary inputs had to be obtained, and many points to be clarified, by intense and sometimes even controversial discussions with many amateurs and even some professionals. Thus specific thanks deserve here all, having proofed patience and contributed in any kind to this chapter.  Our deepest gratitude goes to our wives, children and other family members for their support, interest and patience during all phases before and under the editorial process. Finally of course we generally want to express our warmest thanks to everyone who contributed in any kind to this book .  Marc Trypsteen  Richard Walker   COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

27. Δ px = 174 – 169 = 5px V sin i = 13.08 km/s Western limb Center Eastern limb 170 5885.0 5895.0 5900.0 5890.0 Wavelength λ 2· Δ λ = 1.03Å ( λ 0 = 5889.95) V sin i = 13.11 km/s Pixel 166 174 Western limb Center Eastern limb 2·Δλ - v sin i +v sin i DIRECT VIEW SKETCHES AND ILLUSTRATIONS FOR PROFOUND INTERPRETATION OF THE RECORDED SPECTRUM © 2016 WALKER & TRYPSTEEN

13. H β 5632 H α 7580 H δ 4748 Δλ≈ 1017Å Δλ≈ 771Å Δλ≈ 683 Å Δλ≈ 646 Å H γ 5023 Quasar 3C273, Redshift of the Hydrogen Balmer Lines Wavelengths, determined w ith Vspec at Gaussian fits , are indicated as red shifted I 0.6 1.0 Red shifted, calibrated original scale PLATE 59 λ 0 λ 0 λ 0 COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

28.  Cooling Mechanism by Forbidden Transitions  Here, at the example of the [O III] transitions, the important contribution of the forbidden transitions to the cooling mechanism in emission nebula is considered more closely. The scheme in Fig. 14.8 shows the nebular temperature cycle, displaying the photoionization of the hydrogen atoms by a neighboring OB type star, causing a fast rise of the electron temperature. The generated free electrons collide with already ionized metals such as O III (O ++ ). As mentioned above the kinetic energies of the free moving electrons are within the rough range of the differences 2.5 and 2.8 eV, indicated in Fig. 14.6, causing collision - excitation up to the higher metastable energy levels 1 S 0 and 1 D 2 . Depending on their electron population radiative de - excitation occurs which ends on one of the of the fine - structure levels of O III (O ++ ). This way observable emission lines are generated in the visible wavelength range. In the Spectral Atlas [1] most profiles of the numerous documented emission nebulae show the intense [O III] lines at λ5007 and λ4959, whereas λ4363 appears as a very tiny bump just in the highly excited Planetary Nebula NGC 7009. Therefore the emissions at λ5007 and λ4959 are here the main cooling forces. As a result of consecutive radiative emissions the electron temperature drops and an efficient “cooling” mechanism is activated. After several cycles a thermal equilibrium is reached and the electron temperature stabilizes (Fig. 14.7 and 14.8). COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN 0 1 2 3 4 5 6 7 [ eV ] [S II] [N II] [O III] [Ne III] [O II] 6731 6717 4076 4068 10320 10278 10373 1 0338 6583 6548 5755 3071 3063 5007 4959 4932 4363 4014 3967 3869 3344 1815 1794 3729 3726 7331 7319.6 7318.6 7330

12. PLATE 45 Si II 6347.11 Si II 6371.37 Fe II 5018.44 Si II 5041.02 Fe II 5961.71 ~31 kG Ti II 4805.09 ~30 kG Fe II 4923.93 ~28 kG Fe II 4656.98 ~33 kG Cr II 4558.78 ~34 kG ~44 kG Vega A0V HD215441 B9p Si Babcock‘s Star HD 215441 Mean Magnetic Field Modulus SQUES Echelle Spectrograph slit w idth 70 μ m , JD2456984.4 Estimation of the flux density B of the mean magnetic field modulus from the Zeeman splittings of HD 215441: Ion Landé B Factor Fe II λ5962 1.2 31 kG Fe II λ5018 1.9 30 kG Fe II λ4924 1.7 28 kG Ti II λ4805 1.2 44 kG Fe II λ4657 1.7 33 kG Cr II λ4559 1.2 34 kG Measured mean value: ~33 kG H. Babcock, 1960: ~34 kG COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

22. At the starting position the sum of both angles is α + β = 90 ° . Depending on the chosen or desired geometry the value of 휶 ± 휷 is a typical parameter of the spectrograph. As a result this total angle between the incident rays at the collimator and the diffracted rays collected by the focuser can be fixed going from 90 ° to a small angle value indicated in Fig. 5.3 from C 90 ° to C Littrow , where C corresponds to type C from Fig. 4.10. The selected configuration influences the overall performance but also the limitations of the spectrograph. Turning the focuser to the left so that the angle to the grating normal becomes β < α , e mpirically improves the spectral resolution. At the endpoint the focuser and the collimator are working together representing the idea of the small angle Littrow configuration ( λ B = 2d sin Θ B in Fig. 4.10 ). Which concept can finally be used depends on the optical design of collimator and focuser, the blaze angle of the grating and the resulting linear dispersion. It depends further on the intended area of astronomical applications. COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS 2017 WALKER & TRYPSTEEN

10. H γ 4340.47 H δ 4101.74 H ε 3970.07 He I 4026 Rigel β Ori B8 Iae Regulus α Leo B8 IVn Ca ll 3933.66 He I 4009.27 He I 4120.81 He I 4143.76 Si l 4130.89 Si l 4128.07 He I 4387.93 He I 4471.48 Mg ll 4481.33 He I 4713.15 C ll 4267.27 Fe ll 4303.17 V Fe ll 4351.8 Fe ll 4583.99 Fe ll 4549 Fe ll 4172.45 Fe ll 4233/ 34 Fe ll 4179 PLATE 7 $ Effect of the Luminosity on Spectra of the B - class Fe ll 4629.34 Fe ll 4522.63 Ti ll 4054 Fe l 4046 φ Sgr B8 lll Rigel Regulus φ Sgr Instructive way of pre - senting effects such as: - Negative Luminosity Effect - Rotational Broadening - Collisional / Pressure broadening COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

24. Relatively Flux - calibrated profile Rc ( λ ) Correction - function Ir ( λ ) Ps( λ ) I λ In a rough approximation 퐈퐫 흀 corresponds here to the "attenuation - function" 푫 푻풐풕 흀 , according eq. {8.1} and {8.2}. 퐈퐫 흀 ≈ 푫 푻풐풕 흀 ퟖ . ퟏퟏ Finally the division of the pseudo - continuum 퐏퐬 흀 by the correction - function 퐈퐫 흀 , results in the relatively flux - calibrated profile 퐑퐜 흀 . It shows now the same continuum course like the smoothed reference profile 푴풔 푭풊풕 ( 훌 ) in Fig. 8.6, but appears now overprinted with the accordingly scaled lines of the recorded profile. 퐑퐜 흀 = 퐏퐬 흀 / 퐈퐫 흀 { ퟖ . ퟏퟐ } COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

18. TABLE OF CONTENTS VOLUME 2  1. Physical basics of spectroscopy  2. Electron transitions and formation of the spectra  3. Quantum mechanical aspects of spectroscopy  4. Types and function of dispersive elements  5. Types and function of spectrographs  6. Recording of the spectra  7. Processing of recorded spectra  8. Calibration of the spectra  9. Analysis of the spectra  10. Temperature and luminosity  11. Expansion and contraction  12. Rotation and orbital elements  13. Gravity, abundance and magnetic fields  14. Analysis of emission nebulae  15. Amateurs and astronomical science. This work covers broad theoretical background - and practical approaches necessary for a successful recording and interpretation of astronomical spectra. The perfect companion of the Spectral Atlas and additionally filling the gap with professional environment COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

23. Resolving Power R Spectral Information 150 – 2000 Wide field spectroscopic surveys eg by objective prisms General determination of spectral features eg emissions or absorptions Spectral Energy Distribution (SED curves) Redshift of very faint Quasars and Galaxies General Stellar Spectral Classification Classification of faint Novae and Supernovae Excitation class of emission nebulae 2000 – 9000 Details for Stellar Spectral Classification Spectral details of brighter galaxies Quasars and Supernovae Identification of molecules and elements Analysis of element abundance and metallicity 10,000 – 20,000 Detailed analysis of line profiles eg for disks of Be stars Rotation velocities of planets and stars Stellar temperature, analysis of particular sensitive lines 20,000 – 50,000 Detailed analysis of line profiles ( eg for Wilson Bappu effect) High precision measurements of radial velocities Analysis of solar and stellar magnetic fields by Zeeman effect 50,000 – 100,000 For very large telescopes: Doppler analysis and mapping of winds, circumstellar and proto - planetary disks, flares, interstellar medium > 100,000 For very large telescopes: Atmospheric structures, Thermal broadening, Analysis of Interstellar lines, Chemical composition of exoplanetary atmospheres. For solar telescopes: Detailed analysis of solar surface and granulation Each of the discussed spectrographs has its own characteristics and applications. Depending on which astronomical object will be studied the resolving power of the spectrograph plays a key role in the choice. An important turning point to be able to analyze line profiles and Doppler shifts is a value of R=10,000. Such details are highly demanded by professional astronomers. Therefore high resolution spectrographs are essential for Pro - Am collaborative projects. Tab. 5.4 represents a rough overview of the type of spectral information that can be found in the recorded spectrum with increasing resolving power R [8]. However it makes no sense in any case to strive for the highest possible resolution. As a general rule: The higher the resolving power the longer the required exposure time. Thus for high resolution analysis of faint objects accordingly large professional telescopes are needed. Even with such equipment, for extremely distant and accordingly faint Quasars and Supernovae, low resolution spectrographs are applied. Further for rough stellar classification lowly resolved broadband spectra are preferred, displaying on a glance all relevant, spectral features. COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

15. NH 2 Coma - Spectrum Comet C/ 2009 P1 Garradd PLATE 79 C 2 5165 C 2 4737 CH 4315 C 2 / CH 4383/ 85 P1 Garradd Swan Bands C 2 5130 C 2 4715 C 2 4685 Butane Torch C 3 C 3 C 3 CN CH NH 2 /C 2 NH 2 /C 2 Air Glow 5577 CN C 3 CN CH C 2 NH 2 C 2 C 2 NH 2 NH 2 C 2 CN 3880 Air Glow 6300 / H 2 O C 3 4056 Hg I 4358.34 telluric Influence zones of the individual molecule emission bands [210] COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

8. TABLE 01 Overview on The Spectral Classes PLATE 1 O9.5 B1 B7 A1 A7 F0 F5 G2 G8 K0 K5 Telluric O 2 He I 6678 H α 6563 He I 5876 Na I 5890/ 95 He II 5411 He I 50486 He I 5016 He I 4922 H β 4861 C III 4647/ 51 H γ 4340 He I 4471 He I 4388 H δ 4101 H ε 3970 CH 4300 Ca ll H Mg l 5167 - 83 „Mg Triplet “ Ca I 4227 TiO TiO TiO TiO TiO M0.5 M5 K Vindemiatri x 4‘990K Spica 22‘000K Adhafera 7‘030K Procyon 6‘330K Sun 5‘700K Sirius 10‘000K Altair 7‘550K Arcturus 4‘290K Alterf 3‘950K Alnitak 25‘000K Regulus 15‘000K Antares 3‘600K Ras Algethi 3‘300K TiO Presentation of recorded spectra ideally adapted to didactic teaching COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN

9. PLATE 17 Sun G2V, Highly Resolved Fraunhofer Lines SQUES Echelle Spectrograph K H Ca II 3933.663 Ca II 3968.469 0.2 Blend Fe I/ Fe II Blend Fe I Blend Fe I Fe I 3922.911 Blend Fe I Al I 3944.006 Blend Fe I Blend Fe I Al I 3961.520 Blend Fe I / Ti I b 1 b 2 b 3 b 4 Mg I 5172.68 Mg I 5167.32 Blend Fe I/ Fe II Mg I 5183.60 Fe I 5162.273 Magnesium Triplet G f H γ 4340.462 Fe I 4325.760 CH Fe I 4307.900 Fe I 4315.084 Ca I 4318.652 CH CH D 1 D 2 Na l 5895.924 Na l 5889.951 Ni I 5892.868 Blend H 2 O/ Fe I Blend H 2 O/ Fe I H 2 O 5887.202 H 2 O 5887.641 Fe I 5883.813 H 2 O H 2 O 5894.383 H 2 O Blend H 2 O 5892.375 H 2 O 5885.957 H 2 O 5888.701 H 2 O 5896.814 Blend H 2 O/ V I F E Fe I 5269.537 Fe I 5270.356 Blend Fe I Fe I 5266.555 H β 4861.323 Fe I 4859.741 Blend Fe I/ Ni I/ Ti I/ Y I Ni I 4866.262 Sodium Doublet Telluric Absorption COMPLETE SPECTROSCOPY For AMATEUR ASTRONOMERS © 2017 WALKER & TRYPSTEEN


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