Unit 3 Observing the Night Sky Flashcards
What is Right Ascension?
RA is similar to longitudinal lines across the sky above us. Ra is measured in time from the First Point of Aries, which is now southwest of Pisces and moving towards Aquarius.
What is Declination?
Declination is similar to latitude in the sky above us. Dec is measured from 0 degrees North or South which is above the equator.
How wide is the Zodiacal Band?
8 degrees either side of the declination of the Sun.
What is the declination of Polaris?
+90 degrees.
What is a circumpolar star?
A star is circumpolar if it never dips below the horizon of the observer.
How to calculate if a star is circumpolar?
Declination > 90 - Latitude
If a long exposure camera is pointed at Polaris and captures through the night, how can you calculate the mean arc angle of a star as it moves in the night sky?
Rotational Period of Earth/Exposure Time = 360 Degrees/ Mean Arc Angle
Why is it more difficult for observers in the southern hemisphere to measure the arc angle of a star?
Because thee is not a bright star equivalent to Polaris above the South Pole.
What is happening when stars culminate in the sky?
Stars are on the observer’s meridian and are at their highest in the sky and therefore appear at their brightest.
What are the best conditions for naked-eye observation?
The Moon should be New.
Weather forecast: clear night.
Give examples of events that can be visible with the naked eye.
Meteor shower.
Certain comets.
Lunar eclipse.
Equipment for a naked-eye observation session.
Comfortable chair. Small table. Torch with red filter. Clipboard, pencil and rubber. Warm clothes.
What is dark adapted?
When you spend 20-30 minutes allowing the retina’s rods to become fully sensitive to light.
What is averted vision?
Observation of an object out of the side of your eye so that the retina’s rods become fully sensitive.
What is the Messier Catalogue?
A list of objects visible with the naked-eye but are best viewed with a telescope.
