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Astronomical Techniques Analysis of Moon Observations

Astronomical Techniques Analysis of Moon Observations. Jon Loveday University Of Sussex Department of Physics and Astronomy. Report Contents. Using your own data: description of observations (position & phase) table of your observations

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Astronomical Techniques Analysis of Moon Observations

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  1. Astronomical TechniquesAnalysis of Moon Observations Jon Loveday University Of Sussex Department of Physics and Astronomy

  2. Report Contents • Using your own data: • description of observations (position & phase) • table of your observations • plot of lunar phase against date and estimated value of synodic period • it’s not too late to make further positional and phase observations!

  3. Report Contents • Using class positional data, calculations of: • length of sidereal month • position and precession of ascending node • inclination of orbit to ecliptic • eccentricity • Estimate errors on all these quantities!

  4. Synodic Period

  5. Synodic Period • Determined purely from phase observations • Convert date to day number(2007 Feb 1 12:00 = 32.5) • Convert phase to be monotonically increasing • Fit straight line to obtainsynodic period and error

  6. Class Data • Remaining properties deduced from positional observations • Pooled class data (152 obs) available from website http://astronomy.sussex.ac.uk/~loveday/astroTech • For each observation table includes: • Observer • Date and day number • RA, dec, ecliptic longitude, latitude and their errors • True and mean orbital longitude (longitude difference from ascending node, mean for circular orbit)

  7. Sidereal Period • Plot ecliptic longitude versus day number • Work out which cycle each observation is in (check by using approximate value of period) • Add 360o to longitudes in successive cycles • Identify and remove outliers • Sidereal period can then be deduced from slope of best fit line • NB: Following plots are from a previous year’s data: yours will not be identical

  8. Line of Nodes • Line of nodes isintersection of theecliptic plane andplane of Moon’sorbit • Ascending nodeis South to Northcrossing

  9. Eclipses • We only get an eclipse at full/new moon if the moon is also at a node (crossing the ecliptic)

  10. Ascending Node • Plot ecliptic latitude versus longitude • Nodes arewhere orbitcrosses eclipticplane • Ascending =from –ive to+ive latitude • Descending =ascending + 180

  11. Precession of Nodes • Nodes precess with time • Precession ratecan be estimated bycomparing timeof crossingsover many years

  12. Inclination of Orbit • Given by maximum latitude: try fitting a sincurve to latitude vs longitude plot

  13. Eccentricity of Orbit • Eccentricity may be estimated from plot of (true – mean)orbital longitude vs true longitude • NB not necessarily centred on 0

  14. Summary • Report is due in at midday on Wednesday, 9 January 2008 • Include your observing notebook • Don’t forget to return your cross-staff to Philip Meek or Maria Brook before the end of term and get your £10 deposit back! • Also don’t forget to complete the course evaluation questionnaire via Study Direct

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