Earth Basics
- Earth is tilted by 23.5 degrees
- Earth spins at 1,000 mph
- Earth moves around the Sun at 67,000 mph
- Earth day is 23 hour and 56 mins
- Polaris is 39.5 arcminutes from the True North Celestial Pole
Understanding Degrees
- 180 degrees of the sky is visible above the horizon at anytime
- Stars move across the sky from East to West at ~15 degrees/hour
- Sun and Full Moon are very close to 1/2 degree in diameter or about 1,800 arc-seconds across one's view of the sky
Distances
- 1 astronomical unit (a.u.) = 149.6 million km or 92.9 million miles
- One light year = 5.88 trillion miles, 9.5 trillion km, or 63,000 a.u.
- One parsec = 3.26 light-years
Magnitudes
- Magnitude is the standard to measure the apparent brightness of objects - the lower the number, the brighter the object
- Negative numbers are for the most brilliant objects
- Each magnitude is about 2.5 times brighter or fainter than the next
- Magnitude 6.0 is the faintest objects visible to the naked-eye
- Magnitude 9.0 is 80 times dimmer than the eye can detect
- Magnitude 20.0 is 1,000,000 times dimmer than the eye can detect
Resolving Power
- 1 degree = 60 arc-minutes
- 1 arc-minute = 60 arc-seconds
- 1 arc-second is 1/3,600 of a degree and 1/60 of an arc-minute
- Neptune and Pluto are the only planets which are not visible
- Ring Nebula M57 is about 1 arc-min
- Andromeda Galaxy M31 is about 2.5 degrees wide
Solar Facts
