3.2 Observing The Night Sky Flashcards
What’s declination
If we imagine the Earth at the centre of a giant celestial sphere, declination is almost identical to Latitude.
It is a projection of latitude onto the sphere.
It is the angle of a point above the celestial equator.
The Declination of a star never changes!
What’s right ascension
The RA of a star is the angle between it and the celestial prime meridian.
It is measured in hours and minutes.
What’s the celestial prime meridian
This is the point on the celestial equator on which the sun moves from the southern to the northern hemisphere. Spring Equinox (March 21st)
What’s the zodiacal band
This is the part of the sky that contains the constellations of the zodiac and is the region in which the planets and Moon are located.
It straddles the Ecliptic by 8 degrees on either side.
How do you find your latitude using Polaris
Measure the angular elevation of Polaris from the Northern Horizon
Which way to stars appear to rotate about Polaris
Anti clockwise
How can we determine if a star will be circumpolar using the observer’s latitude and the stars declination
Declination > 90 – latitude
What’s a circumpolar star
This is a star that does not set.
It is above the observer’s horizon all the time.
Which stars are circumpolar depends on the observer’s horizon.
Explain how a star will be circumpolar from a given latitude so long as the declination is > 90 -latitude.
My latitude is 52 degrees.
90-52 = 38 degrees
Therefore any stare with a declination >38 degrees will be circumpolar.
Any star with a declination of 52 degrees will be at my Zenith
Name 4 considerations when planning an observation
Phase of the moon Ideally not visible or less than half Check weather Forecast Likely-hood of a meteor shower Visibility of a planet, Messier/comet.
What equipment should you have on an observation
Equipment
Torch with red filter Does not have such an adverse effect on dark adapted eyes. Reclining chair or table Warm clothes Planisphere
What else is ideal for observing stars
Dark adapted vision 20-30mins of darkness allows retinas rods to become most sensitive Relaxed eye Consider eye-patch Averted vision Focus light onto more sensitive rods e.g. M31
Who was Charles messier
Compiled a list of 110 “fuzzy” objects in the sky.
Named “Ferret of Comets”.
