\contentsline {chapter}{\numberline {1}More than one Sun}{5}
\contentsline {section}{\numberline {1.1}Introduction}{5}
\contentsline {section}{\numberline {1.2}Relative positions in visual double stars}{5}
\contentsline {section}{\numberline {1.3}Naked eye limits}{6}
\contentsline {section}{\numberline {1.4}Optical pairs}{6}
\contentsline {section}{\numberline {1.5}Telescopic pairs}{7}
\contentsline {section}{\numberline {1.6}Binary stars}{7}
\contentsline {subsection}{\numberline {1.6.1}Visual binaries}{7}
\contentsline {subsection}{\numberline {1.6.2}Spectroscopic binaries}{9}
\contentsline {subsection}{\numberline {1.6.3}Astrometric binaries}{10}
\contentsline {section}{\numberline {1.7}Multiple stars}{10}
\contentsline {section}{\numberline {1.8}History of double star observation}{11}
\contentsline {section}{\numberline {1.9}The Great Era of Discovery}{12}
\contentsline {section}{\numberline {1.10}Modern techniques}{13}
\contentsline {section}{\numberline {1.11}The Future}{14}
\contentsline {section}{\numberline {1.12}References}{15}
\contentsline {chapter}{\numberline {2}Why observe double stars?}{17}
\contentsline {section}{\numberline {2.1}Introduction}{17}
\contentsline {section}{\numberline {2.2}Colours}{17}
\contentsline {section}{\numberline {2.3}Tests of resolution}{18}
\contentsline {subsection}{\numberline {2.3.1}Binocular tests}{18}
\contentsline {subsection}{\numberline {2.3.2}Resolution tests for binoculars}{19}
\contentsline {section}{\numberline {2.4}Resolution tests for telescopes}{19}
\contentsline {section}{\numberline {2.5}References}{19}
\contentsline {chapter}{\numberline {3}The Observation of Binocular Double Stars}{25}
\contentsline {section}{\numberline {3.1}Introduction}{25}
\contentsline {section}{\numberline {3.2}Binocular Features}{25}
\contentsline {section}{\numberline {3.3}Aperture, magnification and field diameter}{26}
\contentsline {section}{\numberline {3.4}Binocular mounts}{27}
\contentsline {section}{\numberline {3.5}Tripods}{27}
\contentsline {section}{\numberline {3.6}What can we see?}{27}
\contentsline {section}{\numberline {3.7}Magnitude and separation limits}{27}
\contentsline {section}{\numberline {3.8}Star Colours}{29}
\contentsline {section}{\numberline {3.9}Field drawing}{30}
\contentsline {section}{\numberline {3.10}Summary}{31}
\contentsline {section}{\numberline {3.11}References}{31}
\contentsline {section}{\numberline {3.12}Bibliography}{31}
\contentsline {chapter}{\numberline {4}The scale of binary systems}{33}
\contentsline {section}{\numberline {4.1}Introduction}{33}
\contentsline {section}{\numberline {4.2}Periods greater than 1,000 years}{33}
\contentsline {section}{\numberline {4.3}Periods between 100 and 1,000 years}{34}
\contentsline {section}{\numberline {4.4}Periods between 10 and 100 years}{34}
\contentsline {section}{\numberline {4.5}Periods between 1 and 10 years}{35}
\contentsline {section}{\numberline {4.6}Periods less than 1 year}{35}
\contentsline {section}{\numberline {4.7}References}{35}
\contentsline {chapter}{\numberline {5}Multiple stars and planets}{37}
\contentsline {section}{\numberline {5.1}Binary star formation}{37}
\contentsline {section}{\numberline {5.2}Planets in binary systems}{38}
\contentsline {section}{\numberline {5.3}References}{42}
\contentsline {chapter}{\numberline {6}Is the Sun a double star?}{43}
\contentsline {section}{\numberline {6.1}References}{44}
\contentsline {chapter}{\numberline {7}The orbital elements of a Visual Binary Star}{45}
\contentsline {section}{\numberline {7.1}The true orbit}{45}
\contentsline {section}{\numberline {7.2}The apparent orbit.}{48}
\contentsline {section}{\numberline {7.3}Ephemeris Formulae}{51}
\contentsline {chapter}{\numberline {8}Orbit computation}{53}
\contentsline {section}{\numberline {8.1}Introduction}{53}
\contentsline {section}{\numberline {8.2}A simple geometrical method}{54}
\contentsline {section}{\numberline {8.3}Differential correction of orbits}{56}
\contentsline {chapter}{\numberline {9}Some famous double stars}{63}
\contentsline {section}{\numberline {9.1}Introduction}{63}
\contentsline {section}{\numberline {9.2}Mizar and Alcor}{63}
\contentsline {section}{\numberline {9.3}Castor}{64}
\contentsline {section}{\numberline {9.4}xi UMa}{66}
\contentsline {section}{\numberline {9.5}70 Oph}{69}
\contentsline {section}{\numberline {9.6}zeta Cnc}{71}
\contentsline {section}{\numberline {9.7}References}{72}
\contentsline {chapter}{\numberline {10}The resolution of a telescope}{75}
\contentsline {section}{\numberline {10.1}The Airy disk}{75}
\contentsline {section}{\numberline {10.2}The Rayleigh criterion}{76}
\contentsline {section}{\numberline {10.3}The Dawes limit}{77}
\contentsline {section}{\numberline {10.4}The effect of magnification}{79}
\contentsline {section}{\numberline {10.5}The effect of central obstructions}{79}
\contentsline {section}{\numberline {10.6}Using aperture masks}{80}
\contentsline {section}{\numberline {10.7}Below the Rayleigh limit}{81}
\contentsline {section}{\numberline {10.8}Small apertures}{81}
\contentsline {section}{\numberline {10.9}Seeing}{84}
\contentsline {chapter}{\numberline {11}Reflecting telescopes and double star astronomy}{85}
\contentsline {section}{\numberline {11.1}Reflectors versus refractors, optical principles }{85}
\contentsline {section}{\numberline {11.2}Coma and astigmatism}{91}
\contentsline {section}{\numberline {11.3}Impairment of resolution/image quality.}{92}
\contentsline {section}{\numberline {11.4} Practical and observational consequences.}{93}
\contentsline {section}{\numberline {11.5}On the possible occurrence of astigmatism in star tests.}{97}
\contentsline {section}{\numberline {11.6} How to see the diffraction limit of any telescope.}{99}
\contentsline {section}{\numberline {11.7} Achievable results.}{103}
\contentsline {section}{\numberline {11.8} Some advice}{110}
\contentsline {section}{\numberline {11.9}references}{114}
\contentsline {section}{\numberline {11.10}Bibliography}{114}
\contentsline {chapter}{\numberline {12}Simple techniques of measurement}{115}
\contentsline {section}{\numberline {12.1}Background}{115}
\contentsline {section}{\numberline {12.2}The ring micrometer}{115}
\contentsline {section}{\numberline {12.3}The chronometric method}{122}
\contentsline {section}{\numberline {12.4}Illuminated reticle eyepieces}{126}
\contentsline {section}{\numberline {12.5}Practical recommendations}{133}
\contentsline {section}{\numberline {12.6}References}{133}
\contentsline {section}{\numberline {12.7}Bibliography}{133}
\contentsline {chapter}{\numberline {13}Filar micrometer}{135}
\contentsline {subsection}{\numberline {13.0.1}Position angle}{139}
\contentsline {subsection}{\numberline {13.0.2}Separation}{140}
\contentsline {section}{\numberline {13.1}References}{146}
\contentsline {chapter}{\numberline {14}The Diffraction Grating Micrometer}{147}
\contentsline {section}{\numberline {14.1}Introduction}{147}
\contentsline {section}{\numberline {14.2}The Instrument}{148}
\contentsline {section}{\numberline {14.3}The measurements}{149}
\contentsline {section}{\numberline {14.4}Construction}{150}
\contentsline {section}{\numberline {14.5}Observing}{152}
\contentsline {section}{\numberline {14.6}Disadvantages }{154}
\contentsline {section}{\numberline {14.7}Accuracy}{154}
\contentsline {section}{\numberline {14.8}Conclusions}{156}
\contentsline {section}{\numberline {14.9}References}{157}
\contentsline {chapter}{\numberline {15}CCD Camera Observations}{159}
\contentsline {section}{\numberline {15.1}Introduction}{159}
\contentsline {section}{\numberline {15.2}Principles of CCD Double Star Astrometry}{161}
\contentsline {subsection}{\numberline {15.2.1}The `Astrometric Fitting' Method}{161}
\contentsline {subsubsection}{\numberline {15.2.1.1}`Matching' the image to a star catalog}{162}
\contentsline {subsubsection}{\numberline {15.2.1.2}Measuring unknown pairs}{162}
\contentsline {subsection}{\numberline {15.2.2}The `Plate Scale and Image Orientation' Method}{163}
\contentsline {subsubsection}{\numberline {15.2.2.1}Determining the image scale (E) and image orientation ($\Delta $)}{164}
\contentsline {subsubsection}{\numberline {15.2.2.2}Measuring unknown pairs}{166}
\contentsline {section}{\numberline {15.3}Special-purpose software}{167}
\contentsline {section}{\numberline {15.4}Mathematical Considerations}{169}
\contentsline {subsection}{\numberline {15.4.1}Position of Stellar Image - Intensity Centroid and PSF match}{169}
\contentsline {subsubsection}{\numberline {15.4.1.1}The Point Spread Function}{169}
\contentsline {subsubsection}{\numberline {15.4.1.2}Intensity Centroid and PSF fitting}{171}
\contentsline {subsection}{\numberline {15.4.2}Position of Double-Star Images}{173}
\contentsline {subsubsection}{\numberline {15.4.2.1}PSF Image Modeling}{173}
\contentsline {section}{\numberline {15.5}Considerations Related to Atmospheric Effects}{175}
\contentsline {subsection}{\numberline {15.5.1}Refraction}{176}
\contentsline {subsection}{\numberline {15.5.2}Turbulence ('seeing?)}{176}
\contentsline {subsection}{\numberline {15.5.3}Dispersion}{178}
\contentsline {section}{\numberline {15.6}Considerations Related to Taking and Processing CCD Images}{180}
\contentsline {subsection}{\numberline {15.6.1}Image Sampling and Pixel Size}{180}
\contentsline {subsection}{\numberline {15.6.2}Polar alignment}{181}
\contentsline {subsection}{\numberline {15.6.3} Exposure - Signal-to-Noise Ratio}{182}
\contentsline {subsection}{\numberline {15.6.4}Exposure: Dynamic Range}{184}
\contentsline {subsection}{\numberline {15.6.5}Filters}{185}
\contentsline {subsection}{\numberline {15.6.6}Autoguiding}{185}
\contentsline {subsection}{\numberline {15.6.7}Science images}{185}
\contentsline {subsection}{\numberline {15.6.8}File formats}{186}
\contentsline {subsection}{\numberline {15.6.9}Flats and Darks}{186}
\contentsline {section}{\numberline {15.7}Considerations Related to Image Analysis}{187}
\contentsline {subsection}{\numberline {15.7.1}Are E and ? constant across your entire FOV?}{187}
\contentsline {subsection}{\numberline {15.7.2}WDS `Calibration pairs' and `Synthetic calibration pairs'}{188}
\contentsline {subsection}{\numberline {15.7.3}Summing Images}{188}
\contentsline {subsection}{\numberline {15.7.4}What if I can't get an astrometric match to my image?}{189}
\contentsline {section}{\numberline {15.8}Accuracy and Reliability}{190}
\contentsline {section}{\numberline {15.9}Assessing the accuracy and Reliability of your measurements}{190}
\contentsline {subsection}{\numberline {15.9.1}Precession}{191}
\contentsline {section}{\numberline {15.10}Reporting Your Measures}{192}
\contentsline {section}{\numberline {15.11}References}{193}
\contentsline {chapter}{\numberline {16}Lucky Imaging}{195}
\contentsline {section}{\numberline {16.1}Introduction}{195}
\contentsline {section}{\numberline {16.2}Seeing and resolution}{195}
\contentsline {section}{\numberline {16.3}Lucky imaging}{196}
\contentsline {section}{\numberline {16.4}Choice of cameras}{196}
\contentsline {section}{\numberline {16.5}The role of filters}{197}
\contentsline {section}{\numberline {16.6}Setting the exposure time}{198}
\contentsline {section}{\numberline {16.7}Selection of images}{199}
\contentsline {section}{\numberline {16.8}Image Processing}{200}
\contentsline {section}{\numberline {16.9}Anisoplanatic effects}{201}
\contentsline {section}{\numberline {16.10}Calibration of the image scale}{203}
\contentsline {section}{\numberline {16.11}Determining the position angle}{203}
\contentsline {section}{\numberline {16.12}Accuracy of measurements}{204}
\contentsline {section}{\numberline {16.13}Reproducibility}{207}
\contentsline {section}{\numberline {16.14}Dealing with large d$\Delta $m pairs}{209}
\contentsline {section}{\numberline {16.15}Limitations}{210}
\contentsline {section}{\numberline {16.16}Measuring intensities and d$\Delta $m}{211}
\contentsline {section}{\numberline {16.17}Colour composites}{214}
\contentsline {section}{\numberline {16.18}Concluding remarks}{216}
\contentsline {section}{\numberline {16.19}Acknowledgements}{216}
\contentsline {section}{\numberline {16.20}references}{216}
\contentsline {chapter}{\numberline {17}The DSLR Camera}{217}
\contentsline {chapter}{\numberline {18}How to measure the minima of eclipsing binaries; an amateur's experiences}{225}
\contentsline {subsection}{\numberline {18.0.1}Algol stars (EA)}{225}
\contentsline {subsection}{\numberline {18.0.2}Beta Lyrae stars (EB)}{226}
\contentsline {subsection}{\numberline {18.0.3}W UMa (EW)}{226}
\contentsline {section}{\numberline {18.1}\bf Some light curves}{236}
\contentsline {section}{\numberline {18.2}\bf Some typical light curves}{237}
\contentsline {section}{\numberline {18.3}Conclusion }{239}
\contentsline {chapter}{\numberline {19}Occultations}{241}
\contentsline {section}{\numberline {19.1}Introduction}{241}
\contentsline {section}{\numberline {19.2}Observation}{242}
\contentsline {section}{\numberline {19.3}Double stars}{243}
\contentsline {section}{\numberline {19.4}Visual Observations}{244}
\contentsline {section}{\numberline {19.5}Photoelectric Observations}{244}
\contentsline {section}{\numberline {19.6}Summary}{247}
\contentsline {section}{\numberline {19.7}References}{247}
\contentsline {chapter}{\numberline {20}What the amateur can contribute}{249}
\contentsline {section}{\numberline {20.1}Introduction}{249}
\contentsline {chapter}{\numberline {21}Some active amateur double star observers}{255}
\contentsline {section}{\numberline {21.1}Introduction}{255}
\contentsline {section}{\numberline {21.2}USA}{255}
\contentsline {section}{\numberline {21.3}France}{255}
\contentsline {section}{\numberline {21.4}Germany}{261}
\contentsline {section}{\numberline {21.5}Hungary}{262}
\contentsline {section}{\numberline {21.6}Spain}{262}
\contentsline {section}{\numberline {21.7}South Africa}{266}
\contentsline {section}{\numberline {21.8}United Kingdom}{266}
\contentsline {section}{\numberline {21.9}references}{266}
\contentsline {chapter}{\numberline {22}An observing session}{269}
\contentsline {section}{\numberline {22.1}The telescope}{269}
\contentsline {section}{\numberline {22.2}The micrometer}{269}
\contentsline {section}{\numberline {22.3}Other accessories}{270}
\contentsline {section}{\numberline {22.4}Measurement plan}{271}
\contentsline {section}{\numberline {22.5}Measurement}{272}
\contentsline {section}{\numberline {22.6}Reducing observations}{272}
\contentsline {chapter}{\numberline {23}Some useful formulae}{275}
\contentsline {section}{\numberline {23.1}\bf Introduction}{275}
\contentsline {section}{\numberline {23.2}Dating observations}{275}
\contentsline {section}{\numberline {23.3}Position Angle and Separation}{277}
\contentsline {section}{\numberline {23.4}Precessing the Position Angle}{279}
\contentsline {section}{\numberline {23.5}Differential Atmospheric Refraction}{280}
\contentsline {section}{\numberline {23.6}Estimating Double Star Magnitudes}{281}
\contentsline {section}{\numberline {23.7}Triple Stars}{282}
\contentsline {section}{\numberline {23.8}Observing Double Stars with an Altazimuth Mounted Telescope}{283}
\contentsline {subsection}{\numberline {23.8.1}The Position Angle}{284}
\contentsline {subsection}{\numberline {23.8.2}Field Rotation}{284}
\contentsline {subsection}{\numberline {23.8.3}The Separation}{286}
\contentsline {subsection}{\numberline {23.8.4}Errors}{286}
\contentsline {subsection}{\numberline {23.8.5}Computer programs}{287}
\contentsline {chapter}{\numberline {24}Catalogues}{289}
\contentsline {section}{\numberline {24.1}General Catalogues}{289}
\contentsline {subsection}{\numberline {24.1.1}\bf Northern hemisphere}{289}
\contentsline {subsection}{\numberline {24.1.2}\bf Southern hemisphere}{289}
\contentsline {subsection}{\numberline {24.1.3}\bf All sky catalogues}{290}
\contentsline {section}{\numberline {24.2}Interferometric data}{293}
\contentsline {section}{\numberline {24.3} Double star nomenclature}{294}
\contentsline {chapter}{\numberline {25}Publication of results}{295}
\contentsline {section}{\numberline {25.1}Introduction}{295}
\contentsline {subsection}{\numberline {25.1.1}Identifier:}{295}
\contentsline {subsection}{\numberline {25.1.2}Catalogue: }{296}
\contentsline {subsection}{\numberline {25.1.3}Mean position angle: }{296}
\contentsline {subsection}{\numberline {25.1.4}No of PA measures: }{296}
\contentsline {subsection}{\numberline {25.1.5}Mean separation: }{296}
\contentsline {subsection}{\numberline {25.1.6}No of separation measures: }{296}
\contentsline {subsection}{\numberline {25.1.7}Mean epoch:}{296}
\contentsline {subsection}{\numberline {25.1.8}Observer: }{297}
\contentsline {subsection}{\numberline {25.1.9}Orbit residuals: }{297}
\contentsline {chapter}{\numberline {26}Appendix Brief biographies }{299}
\contentsline {section}{\numberline {26.1}Andreas Alzner }{299}
\contentsline {section}{\numberline {26.2}Rainer Anton}{299}
\contentsline {section}{\numberline {26.3}Graham Appleby }{299}
\contentsline {section}{\numberline {26.4}Bob Argyle }{300}
\contentsline {section}{\numberline {26.5}Owen Brazell }{300}
\contentsline {section}{\numberline {26.6}Robert K. Buchheim}{300}
\contentsline {section}{\numberline {26.7}Rafael Caballero}{301}
\contentsline {section}{\numberline {26.8}Andreas Maurer }{301}
\contentsline {section}{\numberline {26.9}Michael Ropelewski}{301}
\contentsline {section}{\numberline {26.10}Christopher Taylor }{301}
\contentsline {section}{\numberline {26.11}Tom Teague }{302}
\contentsline {section}{\numberline {26.12}Nils Turner }{302}