Astronomical techniques analysis of moon observations
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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 l.jpg

Astronomical TechniquesAnalysis of Moon Observations

Jon Loveday

University Of Sussex

Department of Physics and Astronomy


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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!


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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!



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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


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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)


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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


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Line of Nodes

  • Line of nodes isintersection of theecliptic plane andplane of Moon’sorbit

  • Ascending nodeis South to Northcrossing


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Eclipses

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


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Ascending Node

  • Plot ecliptic latitude versus longitude

  • Nodes arewhere orbitcrosses eclipticplane

  • Ascending =from –ive to+ive latitude

  • Descending =ascending + 180


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Precession of Nodes

  • Nodes precess with time

  • Precession ratecan be estimated bycomparing timeof crossingsover many years


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Inclination of Orbit

  • Given by maximum latitude: try fitting a sincurve to latitude vs longitude plot


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Eccentricity of Orbit

  • Eccentricity may be estimated from plot of (true – mean)orbital longitude vs true longitude

  • NB not necessarily centred on 0


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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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