Topic 4

• What does AST stand for in timekeeping?

  Apparent Solar Time
• What is Apparent Solar Time?


  It is the time according to the Sun at your location, also known as sundial time.
• What is the phase of the Moon called that occurs between new and quarter Moon?

  Crescent
• What does EOT stand for and what does it represent?

  Equation of Time; it represents the adjustment needed because the Sun sometimes travels faster or slower through the sky due to Earth's tilt and elliptical orbit.
• How is the Equation of Time calculated?

  EOT = AST - MST
• What is an equinox?


  It is when the Sun crosses the ecliptic, resulting in a declination of the Sun equal to 0.
• At what point does the Right Ascension (RA) equal 0?

  At the vernal equinox on March 21st.
• Where will the Sun be directly overhead during the equinox?

  On the equator.
• What is the phase of the Moon called that occurs between quarter and full Moon?

  Gibbous
• What does GMT stand for?

  Greenwich Mean Time
• What is Mean Solar Time (MST)?

  MST is Apparent Solar Time adjusted for the Equation of Time.
• How long is a sidereal day?

  23 hours and 56 minutes
• What is a solstice?

  It is when the Sun is at its highest (summer) or lowest (winter) point in the sky, indicating maximum positive or negative declination.
• Where will the Sun be directly overhead during the summer solstice?

  On the Tropic of Cancer.
• What does AST stand for in astronomy?

  Apparent Solar Time
• What is Apparent Solar Time?


  It is the time according to the Sun at your location, also known as sundial time.
• What phase of the Moon is described as being between new and quarter Moon?

  Crescent
• What does EOT stand for?

  Equation of Time
• Why is the Equation of Time (EOT) necessary?


  It accounts for the variation in the Sun's speed across the sky due to the Earth's tilt and elliptical orbit.
• How is EOT calculated?

  EOT is calculated as EOT = AST - MST.
• What is an equinox?

  It is when the Sun crosses the ecliptic, resulting in a declination of the Sun equal to 0.
• What is the significance of the vernal equinox?

  At the vernal equinox (21st March), the right ascension (RA) of the Sun is 0, and it is directly overhead at the equator.
• What phase of the Moon is described as being between quarter and full Moon?

  Gibbous
• What does GMT stand for?

  Greenwich Mean Time
• What does MST stand for?

  Mean Solar Time
• How is Mean Solar Time (MST) related to Apparent Solar Time (AST)?

  MST is AST adjusted for the Equation of Time (EOT).
• What is a sidereal day?

  A sidereal day is 23 hours and 56 minutes, the time it takes for the Earth to rotate so that the stars appear in the same position in the sky.
• What is a solstice?


  A solstice occurs when the Sun is at its highest (summer) or lowest (winter) point in the sky, indicating maximum positive or negative declination.
• Where is the Sun directly overhead during the summer solstice?

  The Sun is directly overhead on the Tropic of Cancer during the summer solstice.
• Where is the Sun directly overhead during the winter solstice?

  The Sun is directly overhead on the Tropic of Capricorn during the winter solstice.
• What is a synodic day?

  A synodic day is 24 hours, the time it takes for the Earth to rotate so that the Sun returns to the same position in the sky.
• How are time zones generally structured?

  Time zones are on average 15° apart, with each zone mostly differing by one hour from the next.
• What does UT stand for?

  Universal Time
• How is Universal Time (UT) related to Greenwich Mean Time (GMT)?

  UT is equivalent to GMT.
• What does waning refer to in terms of the Moon?

  Waning refers to the Moon getting smaller each night.
• What does waxing refer to in terms of the Moon?

  Waxing refers to the Moon getting larger each night.
• What is the Equation of Time (EOT)?

  A correction to local time on sundials
• How is the Mean Solar Time (MST) obtained?

  By adjusting Apparent Solar Time (AST) with EOT

  
• What does a sundial show?

  Apparent Solar Time (AST)
• How can local MST be compared with Greenwich Mean Time (GMT)?

  By determining the observer's longitude