Credit/Permission: For text, © David Jeffery. For figures etc., as specified with the figure etc. / Only for reading and use by the instructors and students of the UNLV astronomy laboratory course.
Sub Tasks:
Why is the physical rotation period of the
Earth relative to the
inertial frame of the
fixed stars
(i.e., the
sidereal day = 86164.0905 s
= 1 day - 4 m + 4.0905 s (on average))
SHORTER than the
solar day = current mean value 86400.002 s
(i.e., the solar noon to
solar noon period)?
Answer in sentences with reference to the figure below
(local link /
general link: sidereal_solar_time_2.html).
HINT: You have to consider the Earth's
revolution around the Sun.
What is a great circle?
What is a small circle?
Answer in sentences.
The horizon
is a _________________ circle on the celestial sphere.
Sub Tasks:
HINT: The figure below
(local link /
general link: declination_altitude.html)
might stimulate your memory.
Fill in the blanks below:
By eye-balling the
celestial globe
(if the instructor
remembered to put it out for you) or the
sky map shown in the figure above
(local link /
general link: sky_map_all_sky.html),
what is the approximate average
declination (Dec or δ) of:
Using
TheSky
find the southernmost
star
(i.e., the star closest to the
SCP) with
TheSky
reference magnitude
(which must be close to
the apparent V magnitude)
brighter (i.e., less) than or equal to 3.00 (i.e., ≤ 3.00).
What is its:
Complete the following sentences:
Sub Tasks:
Sub Tasks:
Sub Tasks:
What zodiac sign
contained the Sun when you
(or your group leader if appropriate) were born (i.e., what is
your zodiac sign)
and what
zodiac constellation
contained the Sun when you
(or your group leader if appropriate) were born?
See
Wikipedia: Zodiac: Twelve signs
(Table of Dates: Scroll down ∼ 5%)
(in the column for
tropical zodiac)
and
Wikipedia: Zodiac: Constellations
(Table of Dates: scroll down ∼ 5%)
(in the column for
IAU boundaries).
How the night sky changes
as the Sun moves along the
ecliptic is explicated in
the figure below
(local link /
general link: zodiac_ecliptic.html)
this task
and applet figure above
(local link /
general link: naap_zodiac.html)
this task
(if it is working which it probably is NOT).
Sub Tasks:
Sub Tasks:
You will have convert today's date in to month count from the beginning of the
year with the
decimal fraction included.
For example, if it is June 21, t_month ≅ 5.67.
In your answer, you will have to convert time from hours to hours and minutes.
Sub Tasks:
Sub Tasks:
Northern Hemisphere,
which is longer day or
night on this day? ________________________
In the Northern Hemisphere,
which is longer day or
night on this day? ________________________
HINT: What
latitude circle
is always cut in half by the
Earth's
terminator.
Sub Tasks:
Diagram:
HINTS:
The general formulae relating
altitude AN/S
(upper/lower case for altitude
from due north/due south)
along the meridian,
declination (δ),
and latitude (L)
(with southern latitudes counted as
negative numbers)
are:
For proof of these formulae, see the figure above
(local link /
general link: declination_altitude.html).
Sub Tasks:
Sub Tasks:
Sub Tasks:
Does the eccentricity
of the Earth's orbit
have any effect on the Earth's climate?
Explain.
Sub Tasks:
Note the terms
solstice and equinox
have two meanings: one is the event and the other
is the place on the
celestial sphere
where the event occurs.
Fill in the data in the table below following the instructions below.
Two-digit precision suffices.
Sub Tasks:
What is the angular velocity in degrees per day of the
Earth? R_e = _________________________
Using the exact period result
25,771.5 Julian years, what is the
angular velocity in degrees per day of
vernal equinox
westward along the
ecliptic? R_v = _________________________
The Sun
moves eastward
and
the vernal equinox
moves westward.
Let's take eastward as positive
and westward as negative.
So the angular velocity of the
vernal equinox is minus the value you calculated above
(i.e., R_v = - |R_v|).
The time t for the Sun to lap the
vernal equinox satisfies
the equation
Answer: We have
Explain why the equatorial coordinates
for astronomical objects beyond the
Solar System
have to be updated every few years. Give the main reason and a second reason.
EOF
End of Task
End of Task
AN(NCP) = L ,
where L is latitude
(counted as negative if
south latitude)
and the AN(NCP) is counted as negative if the
NCP is
below the horizon.
AN/S = (±)N/S(L - δ) + 90°
δ = L +(±)N/S(90° - AN/S)
L = δ +(±)N/S( AN/S - 90°)
End of Task
AN/S = 90°+(±)N/S(L-δ) ,
where the upper/lower case is for
altitude from
due north/due south,
L is the local latitude
(counting southern latitudes as negative),
and δ is the declination (Dec)
of the astronomical object.
For the last column, you will need the lower case
(i.e., AS = 90°-N/S(L-δ))
since the
Sun at an
altitude measured from
due south.
_____________________________________________________________________
Table of Solstice and Equinox Data
_____________________________________________________________________
Sun Position Fiducial Date RA Dec Altitude of the Sun
(h) (degrees) in Las Vegas at
Solar Noon
(degrees)
_____________________________________________________________________
vernal equinox
summer solstice
fall equinox
winter solstice
_____________________________________________________________________
360° = (R_e - R_v)t
What is t in days?
Since the answer requires
double-precision math,
we will just give the result:
t = 360°/(R_e - R_v) = 360°/(0.985609113115 + 0.0000382448) = 365.2421904276 days.
The accepted
solar year = 365.2421897 days (J2000).
So the two values agree to 8 digit places. The calculation wasn't so bad.