Tutorial on Celestial Coordinates and Stellarium

Introduction

• Types of Coordinates: Local (Altitude & Azimuth) and Celestial/Equatorial (Right Ascension & Declination)
• Program Used: Stellarium, a planetarium software.

Local Coordinates: Altitude & Azimuth

• Altitude: Angle above the horizon
  • Measured in degrees, can also be in arc minutes, and arc seconds.
  • Horizon: 0° Altitude
  • Zenith: +90° Altitude (directly overhead)
  • Nadir: -90° Altitude (directly below)
• Azimuth: Compass bearing around the horizon
  • Due North: 0° Azimuth
  • Due East: 90° Azimuth
  • Due South: 180° Azimuth
  • Due West: 270° Azimuth
  • Completes 360° back to north
• Example: Position of the Sun in Stellarium
  • Sun's Altitude: 47° 59 arc minutes, approx. 48° above the horizon.
  • Sun's Azimuth: 101°, east-southeast.
• Meridian Line: From due south through the zenith to due north.
• Zenith Passage: When an object crosses the meridian, reaching max altitude.
  • Important for astronomical observations due to minimization of atmospheric interference.

Celestial Coordinates: Right Ascension & Declination

• Connection to Terrestrial Coordinates
  • Declination (Dec): Celestial Latitude
    • Equator (Celestial): 0° Dec
    • North Celestial Pole: +90° Dec
    • South Celestial Pole: -90° Dec
  • Right Ascension (RA): Celestial Longitude
    • Measured in hours, minutes, and seconds to tie into Earth's rotation (24h = 360°).
    • Spring Equinox: 0h RA (arbitrary fixed point)
• Equatorial Mount Mode in Stellarium
  • Keeps celestial equator horizontal instead of the horizon.
  • Useful for understanding celestial coordinates.
• Simulation Exercises: Understanding the declination and right ascension of stars through Stellarium and University of Nebraska astronomy simulator.

Practical Application

• Stellarium Features: Configuration and visualization for celestial objects.
  • Equatorial grid to view right ascension and declination.
  • Ground on/off to view entire celestial sphere.
• Object Observation: Align telescope with known coordinates to locate objects.
• Celestial Coordinate Changes: Understanding time-based changes and precession effects.

Important Tips

• Viewing Conditions: Optimal observation at highest possible altitude due to less atmospheric distortion.
• Coordinate Conversions: Understanding the relationships and conversions between local and celestial coordinates.
• Playing Around in Stellarium: Familiarizing oneself with dragging stars and observing changes in coordinates.

Summary

• Astronomical observations rely heavily on both local and celestial coordinate systems.
• Tools like Stellarium are essential for visualizing and planning observations.
• Understanding the basic concepts and practical applications of altitude, azimuth, right ascension, and declination is crucial for anyone studying or practicing astronomy.