observation of Thin Lunar Crescents
by Byron Soulsby
I first presented software to find the best
times for observing thin lunar cresents at the 7th NACAA in 1976
but have never taken this further other than to attempt continuous
observation of morning events due to a very favourable easterly outlook
from my observatory.
search of the internet for information on the best times to find and
observe thin lunar crescents yielded a surprising result - software for
the determination of Accurate
Times and ephemerides for all TLCs (Ref
software meets the Moslem faith requirements in that the true date for
beginning of each calendar month is known as indicated by the first
observable thin lunar crescent, or TLC. At this instant accurate
times for prayer and the true location of Mecca can be deduced to meet
Observation of a TLC at
6:15 am, summer time on
the morning of 16 February 2007 some two days before new moon, revealed
an easily observable crescent . The age of the TLC was
as -45 hours old.
The Accurate Times
downloaded and run to compare with the above observation .
The results were extremely encouraging giving a TLC
geocentric age of -44h59m18s, almost exacltly equal to that observed.
The software results were as follows:
By the Name of Allah
Jordanian Astronomical Society (JAS)
Accurate Times 5.1, By Mohammad Odeh
- Calculations for Muharram 1428 AH Waning Crescent (Old, Morning).
- Crescent Visibility on: Friday 16/02/2007 CE
- Calculations are Done at User Time at: 05:15:00 LT
- Calculations are Geocentric.
- AUSTRALIA ACT Theodore, Long: 149:07:01.0, Lat: -35:27:05.0,
- Summer time is: Off
- Height above mean sea-level affects rise and set events.
- Refraction Settings: Temperature: 10 °C
Pressure: 1010 mb
- Delta T: 65.02 Second(s)
- G. Conjunction Time: 18/02/2007 CE, 02:14:18 LT
- Julian Date at Time of Calculations: 2454147.30208
- Moorise: 03:18:49
Age: -44H 59M 18S
- Sunrise: 05:31:57
Moon Lag Time: +02H 13M 08S
- G. Moon Right Ascension: +20H 18M 49S G. Moon
- G. Sun Right Ascension: +21H 55M 47S G.
Sun Declination: -12°:36':28"
- G. Moon Longitude:
G. Moon Latitude: -03°:41':55"
- G. Sun Longitude:
G. Sun Latitude: -00°:00':00"
- G. Moon Altitude:
G. Moon Azimuth: +105°:04':21"
- G. Sun Altitude:
G. Sun Azimuth: +109°:23':09"
- G. Relative Altitude:
G. Elongation: +25°:24':14"
- G. Relative Azimuth:
G. Phase Angle: +154°:32':03"
- G. Crescent Width:
Moon Semi-Diameter: +00°:16':05"
- G. Illumination: 04.86
G. Horizontal Parallax: +00°:59':02"
- G. Magnitude:
G. Distance: 371470.78 Km
- According to Odeh Criteria, using the following values at Best Time:
* Moon-Sun Topocentric Relative Altitude
* Topocentric Crescent width = +00°:01':30" (1.50')
* q = 25.22
* The Crescent Visibility is: Easily Visible By Naked Eye.
- Date format: dd/mm/yyyy.
- The Prefix 'G.' means Geocentric, and 'T.' means Topocentric.
- For New Crescent: Moon Lag Time = Moonset - Sunset.
- For Old Crescent: Moon Lag Time = Sunrise - Moonrise.
- For New Crescent: Best Time = Sunset + 4/9 (Moon Lag Time).
- For Old Crescent: Best Time = Sunrise - 4/9 (Moon Lag Time).
This software meets all of my requirements (Ref 3) for
TLCs without further ado, especially as it includes early morning
events as described above. As my westerly horizon is full of
Tuggeranong Hill, so to see evening TLCs requires a short trip in the
achieve a clear westerly horizon.
Astronomical Society of
New South Wales, Proceedings of the 7th NACAA, session 7A
"Thin Lunar Crescents", Byron W Soulsby CAS.
2. "Accurate Times" from http://www.icoproject.org/accut.html
for 2007 at Theodore
Produced by the Theodore
Lunar Observatory, Australia
- 2007 February 19