Topic 3 - 4

Question 1

Prime meridian, where is it? What is the role?

Answer 1

Greenwich, serparates East and west

Question 2

Where do stars rise and set?

Answer 2

They rise in the east and set in the west

Question 3

What is a circumpolar start

Answer 3

they are the stars that are always above the horizon, all the time, during the whole year.

Question 4

What is the azimuth?

Answer 4

Angle clockwise (east) starting from the north side of local meridian.

Question 5

what does it mean when a star is transiting?

Answer 5

Highest possible point above the horizon

Question 6

Declination

Answer 6

How high it is north (-) or south (-) from the celestial equator

Question 7

What’s important about the vernal equinox?

Answer 7

It is located on the 0 hour right acension

Question 8

Sidereal day

Answer 8

Full rotation period of earth - 24h. - 23h56 solar time

1 deg = 4 min

Question 9

Solar Day:

Answer 9

“synodic” period fo the sun- time interval between sun transiting and the next itme the sun is transiting. -

Question 10

March 20th

Answer 10

NH: spring
SH: fall
dec: 0
Ra : 0

Question 11

June 21st

Answer 11

NH: summer
SH: winter
dec: +23.5
Ra : 6h

Question 12

sep 22

Answer 12

NH: fall
SH: spring
dec: 0
Ra : 12h

Question 13

Winter Solstice

Answer 13

NH: winter
SH: summer
dec: -23.5
Ra : 18h

Question 14

Apparent solar time:

Answer 14

using sundials, hour angle of the sun + 12h

Question 15

Mean solar time:

Answer 15

hour angle of the fictitious mean sun that changes declination at a constant rate throughout the year.
the average length of the solar day (24h) but varies continuously with longitude. Clock is et according to local meridian

Question 16

Standard time:

Answer 16

this is the system we use. The lenght of the day equals the mean solar time, but you synchronize your clock according to the nearest reference meridian

Question 17

Time equation

Answer 17

AST - MST = AMS (graph)

Question 18

two causes for seasons:

Answer 18

Daytime duration

angle how the sun hits -> less energy / area

Question 19

The lenght of the tropical year

Answer 19

From winter solstice to the next winter solstice

Question 20

Julian calendar

Answer 20

year length = 365.25
every 4 years a day is added
problem: after each year - 11 minutes extra

Question 21

gregorian calendar

Answer 21

1. on oct 4 1582 -> 11 day lag fixed by making it oct 15
   2, changed the average lenght of the calendar, making it shorter.
   the years that are a multiuple of 4 are leap years (366)
   years that are multiples of 100 are normal years (365 days) instead of 366
   yaers that are mutliples of 400 - these remaine leap yars 366

in 400 years , 97 leap years , compared to 100, and the new average of the year is 365.2425
0.0003 day / year