Equatorial System and Star Charts
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Virginia Tech *
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MISC
Subject
Astronomy
Date
Apr 3, 2024
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docx
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3
Uploaded by SuperHumanElementJellyfish37
Sarah Johnson
Equatorial System and Star Charts
Examine the rectangular star maps. It represents a portion of the celestial sphere as a rectangle. Distortions occur when a 3D sphere is drawn as a flat rectangle. The distortions are severe near the top and bottom of the map. The distortion is quite workable for most purposes in the center two-thirds of the map. It’s similar to the rectangular maps of the Earth that grossly distort the landmasses near the north and south poles, but work fine for the major populated areas closer toward the equator. The line running horizontally through the center of the star map represents the celestial equator. Right Ascension (RA) is measured along this line from right to left in units of hours and minutes. Notice the RA
scale at the bottom of the map. Declination (Dec) is measured in degrees perpendicular to the celestial equator. The scales are on the left and right edges of the map. Print out a copy of the star chart.
1.
Find on the map the “topmost” star of the constellation Libra. a.
What is its Right Ascension in hours and minutes? ______15 hours 17 min________
b.
What is its Declination in degrees? _____-9 degrees___________
2.
The sun’s location at the first day of each season in the northern hemisphere is given in the table below. Plot its position on the rectangular star map for each date and label it with the season.
Season
RA
Dec
Autumn
12h 0m
0
o
Winter
18h 0m
-23.5
o
Spring
0h 0m or 24h 0m
0
o
Summer
6h 0m
+23.5
o
3.
Fill in the table below with the constellation closest to the sun’s position (that is, the constellation the sun is ‘in’).
Season
Constellation the Sun is ‘in’
Autumn
Virgo
Winter
Sagittarius
Spring
Pisces
Summer
Gemini
4.
Now that the four principal seasons are plotted, imagine where the sun might be on dates between these points. For example, what are the approximate RA and Dec of the sun on October 22? How about May 21 and July 15?
October 22
RA: __13 hours 51 min______
Dec: ____-11 degrees____
May 21
RA: ___3 hours 57 min_____
Dec: ____20 degrees____
July 15
RA: ___7 hours 44 min_____
Dec: ____21 degrees____
The sun always appears on the imaginary line called the ecliptic. The ecliptic can also be thought of as tracing the plane of the Earth’s orbit. 5.
Label the ecliptic on the star chart.
6.
The following table lists the celestial coordinates for the major planets on September 24, 2004. Plot the planet positions on the map and label each planet. Try to use a different color pen than
the sun positions.
Planet
RA
Dec
Mercury
11h 32m
+5
o
Venus
9h 25m
+15
o
Mars
11h 56m
+1
o
Jupiter
12h 0m
+1
o
Saturn
7h 50m
+21
o
7.
Below, fill in the constellation closest to each planet’s position on September 24, 2004:
Planet
Constellation
Mercury
Virgo
Venus
Leo
Mars
Virgo
Jupiter
Virgo
Saturn
Gemini
8.
What can you conclude about the position of the planets relative to the plane of the Earth’s orbit? __________They all orbit the same plane__________________________________
9.
The following table lists the Moon’s coordinates at 5 day intervals for a one month period. Plot the moon’s position on the map and label each position with the date.
Date
RA
Dec
9/24
20h 23m
-25
o
9/29
0h 46m
+3
o
10/4
4h 51m
+26
o
10/9
9h 14m
+21
o
10/14
13h 14m
-7
o
10/19
18h 2m
-28
o
10.
For each of the above dates, fill in the constellation closest to each Moon position.
Date
Constellation
9/24
Capricornus
9/29
Pisces
10/4
Taurus
10/9
Cancer
10/14
Virgo
10/19
Sagittarius
11.
What can you conclude about the Moon’s orbit relative to the plane of the Earth’s orbit? _________________The moon is above or below the plane of the Earth_______________
Summary:
Today I decided to complete the lab titled “Equatorial System and Star Charts”. I have always been interested in astrology and have been familiar with the names of a lot of the signs used in the lab today. It was really cool seeing them on a real star map and being able to establish the moons and seasons of the different astrology signs. I think studying stars is really interesting and have found that this lab and the past lab to be really entertaining to do. I also enjoy relating the stars, moon, planets, and sun together to establish different things.
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