create model of lunar trajectory

[ellemenno]

we need to better understand the motion of the moon relative to an observer viewing the sky from the octagon.

ideally, create a 'security camera' array of viewpoints matching the 8 octagon viewpoints, showing the 18.6yr lunar cycle so we can see the progression of rises and sets.

[ellemenno]

Stellarium will be a valuable reference.

• Control time with J (backwards) and L (forwards). Pressing the key multiple times increases the speed in that direction.
• We can set a custom ground panorama. Maybe we'll head back to Newark for a photo shoot!
• Use F6 to open the location dialog and add locations:
  • Main viewing area: Lat: N° 40° 2' 58.69", Lon: W° 82° 27' 1.02", Elev: 254m

I made the following observations:

• the maximum northern and southern rises are more or less symmetric about due East.
• the maximum northern and southern rises are more or less symmetric about due West.
• the moon rises and sets about 1 hour later each night, so it rises and sets all times of day and night. the moon actually has nothing to do with night (i guess it's rather obvious that night comes from the sun, but i hadn't thought about it before)
• the moon rises and sets in about the same spot roughly every month; once i marked the maximum northern rise, it looked to me that the moon reached it again every 28 days, although the time of day and phase of moon would vary, making it difficult to spot in real life
• the maximum southern rise seems offset from the max northern by about half a cycle
• a maximum northern set follows a maximum northern rise; a maximum southern set follows a maximum southern rise--that same night

[ellemenno]

Also, I read that the moon's rotation, the moon's orbit about the earth, the earth's rotation, and the earth's orbit about the sun are all counterclockwise. Right-hand rule if you point your thumb at Polaris. [ref:Wikipedia]

[tayres]

Nice!!! I see I forgot earth's "wobble". I'm adding that and security cams.

[michelle-aubrecht]

http://astro.unl.edu/naap/motion3/animations/sunmotions.html motions of the sun simulator

[ellemenno]

there are a lot of great simulations on that site: http://astro.unl.edu/animationsLinks.html !

in particular, the following relate well to our project:

• lunar phase simulator
• lunar phase vocabulary
• full moon declination
• moon inclination
• rotating sky explorer
• zodiac simulator

[michelle-aubrecht]

http://astro.unl.edu/classaction/lunarcycles.html

links to the one below: lunar phases simulator

http://astro.unl.edu/classaction/loader.html?filename=animations/lunarcycles/lunarapplet.swf&movieid=lunar_applet&width=840&height=680&version=6.0.0

did you include the one above?

[ellemenno]

i've added some diagrams here:

• http://earthworksbuilder.github.com/images/diagrams/rise-set-max.jpg
• http://earthworksbuilder.github.com/images/diagrams/rise-set-min.jpg

[ellemenno]

Mike gave us some great data from JPL's Horizons tool. Here are the settings:

Ephemeris Type : OBSERVER Target Body : Moon [Luna] [301] Observer Location : user defined ( 82°26'50.0''W, 40°03'10.0''N, 870 ft ) Time Span : Start=2006AD-Sep-01 00:00 UT-4:00, Stop=2006AD-Dec-31, Step=1 m Table Settings : QUANTITIES=4,10; angle format=DEG; refraction model=REFRACTED; RTS flag=TVH Display/Output : download/save (plain text file)

[ellemenno]

added another diagram:

• http://earthworksbuilder.github.com/images/diagrams/alignments.jpg

also found some more good visualization:

• videos - http://www.mogi-vice.com/Pagine/Downloads.html
• graphics - http://astro.wsu.edu/worthey/astro/html/lec-celestial-sph.html

and a nice simple explanation of the major moon motion aspects (nutation is the bobbing motion of the earth that causes the moon to slide from northern rises and sets to southern:

• http://www.esse.ou.edu/fund_concepts/Fundamental_Concepts1/Solar_System/Earths_Rotation.htm

[ellemenno]

here are the azimuth values of the max-min / N-S / rise-sets:

N(0°) max - set: 308°, rise: 52° min - set: 293°, rise: 65° S(180°) min - set: 244°, rise: 116° max - set: 230°, rise: 130°

[ellemenno]

here's the (final?) word on this, official data from JPL's Horizons tool via email, like what Mike gave us. so cool!

for the max rise/sets, i sent the following:

to: horizons@ssd.jpl.nasa.gov subj: JOB body:

!$$SOF
COMMAND= '301'
CENTER= 'coord@399'
COORD_TYPE= 'GEODETIC'
SITE_COORD= '-82.4472222222222,40.0527777777778,0.265176'
MAKE_EPHEM= 'YES'
TABLE_TYPE= 'OBSERVER'
START_TIME= '2006AD-Sep-01 00:00 UT-4:00'
STOP_TIME= '2006AD-Dec-31'
STEP_SIZE= '1 m'
CAL_FORMAT= 'CAL'
TIME_DIGITS= 'MINUTES'
ANG_FORMAT= 'DEG'
OUT_UNITS= 'KM-S'
RANGE_UNITS= 'AU'
APPARENT= 'REFRACTED'
SOLAR_ELONG= '0,180'
SUPPRESS_RANGE_RATE= 'NO'
SKIP_DAYLT= 'NO'
EXTRA_PREC= 'NO'
R_T_S_ONLY= 'TVH'
REF_SYSTEM= 'J2000'
CSV_FORMAT= 'NO'
OBJ_DATA= 'YES'
QUANTITIES= '4,10,13'
!$$EOF

for the min rise sets, i used:

START_TIME= '2015AD-Dec-01 00:00 UT-4:00'
STOP_TIME= '2016AD-Mar-31'

since Fri Sep 1, 2006 + 9.3yrs = Sat Dec 19, 2015