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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

Astronomical TechniquesAnalysis of Moon Observations

Jon Loveday

University Of Sussex

Department of Physics and Astronomy

report contents
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!
report contents3
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!
synodic period5
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
class data
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)
sidereal period
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
line of nodes
Line of Nodes
  • Line of nodes isintersection of theecliptic plane andplane of Moon’sorbit
  • Ascending nodeis South to Northcrossing
eclipses
Eclipses
  • We only get an eclipse at full/new moon if the moon is also at a node (crossing the ecliptic)
ascending node
Ascending Node
  • Plot ecliptic latitude versus longitude
  • Nodes arewhere orbitcrosses eclipticplane
  • Ascending =from –ive to+ive latitude
  • Descending =ascending + 180
precession of nodes
Precession of Nodes
  • Nodes precess with time
  • Precession ratecan be estimated bycomparing timeof crossingsover many years
inclination of orbit
Inclination of Orbit
  • Given by maximum latitude: try fitting a sincurve to latitude vs longitude plot
eccentricity of orbit
Eccentricity of Orbit
  • Eccentricity may be estimated from plot of (true – mean)orbital longitude vs true longitude
  • NB not necessarily centred on 0
summary
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