Astronomy. My first Year Notes
written by Kirstie Calderon Lewis
My own notes of Astronomy First Year lesson 1 - 9. All notes from the lessons and my own work on Astronomy. Important information for quizzes and essays can be find within the notes.
Last Updated
05/31/21
Chapters
9
Reads
917
Lesson Six
Chapter 6
• The first non-magical telescope wasn’t invented until 1608, more than 70 years after von Rheticus.
• The von Rheticus telescope has about as much resolving power as a 12-centimeter-wide Muggle-built telescope (about one arcsecond), but less than 1/20 the light-gathering power.
• Muggles have made so much more progress in technology.
• Their best telescopes are far superior to ours. This technology enables them to make measurements of angular size, phase, optical albedo, and distance from the Sun more accurately than we can. The 100-inch-wide Hubble telescope has 20 times as much resolving power as the von Rheticus model, and the ground-based Keck telescope uses adaptive optics to equal or even better Hubble’s resolving power despite the wobbling of the image caused by the movement of the air.
• The beam of light is a laser beam, which is used for the aforementioned adaptive optics. The movement of the air makes the beam and the nearby stars seem to wobble, but the primary mirror follows the beam and adjusts to it by bending just enough to cancel the wobbling of the beam, thus cancelling the apparent wobbling of the nearby stars as well.
Distance from the Sun
• Von Rheticus - The motion of planets in the sky and calculated the distance of each of the planets from the Sun.
• Telescope to be able to recognize a planet it was pointed at from the magic it reflected and entered into his telescope the distance of each of the planets from the Sun.
• Von Rheticus assumed that all the planets travel around the Sun in a circle.
• A planet’s distance from the Sun isn’t quite constant, because it revolves around the Sun in an ellipse, not a circle.
• The Sun isn’t in the middle of the ellipse. So, the distance he entered for each planet was the average one rather than the current one.
• Mars and Mercury are exceptions. A planet’s distance from the Sun at any specific time can be calculated exactly using a method discovered by Isaac Newton.
Angular Size, Phase and Optical Albedo
• Since Muggles can now find the optical albedo and angular size of these bodies more accurately than we can, we often use their values, presented in the table below, in our calculations.
• The Moon and some of the planets have lighter and darker parts with different specific albedos.
• You will notice that the albedo of each celestial body is constant, whereas its angular size depends upon how far the planet is from Earth. Which varies throughout the day, season, and year.
• Venus has the widest range of angular size, appearing about 6.8 times as large when it is closest to Earth as when it is farthest away.
• Button labelled “S” for Angular size. The angular size is shown in degrees, arcminutes and arcseconds.
• The word degrees are replaced by this symbol o, and standard notation is used for minutes and seconds.
• For example, if you’re looking at a comet, whose angular length is two degrees, 35 arcminutes, and 28 arcseconds, then, since a comet’s length is much greater than its width, you’ll see 2o35'28", whatever its width happens to be.
• Can always obtain the albedo and angular size of a body by consulting a table of values, as a magical person.
• Von Rheticus telescope has two additional buttons aside from the two zoom buttons and the focusing knob? If the telescope is held so that the focusing knob is on the left side, then those two buttons are situated on the top of the wider tube near the middle, where you might hold it to keep it balanced.
• Buttons is labelled “S” for angular size. When you press it, the angular size of the object, expressed in degrees, arcminutes, and arcseconds, appears at the bottom of the field of view in pure red characters.
• The word degrees is replaced by this symbol o, and standard notation is used for minutes and seconds.
• The von Rheticus telescope calculates the phase of an object by measuring its angular length and width and dividing the width by the length.
• Another button on your telescope is labelled “A”. A stands for albedo. The (optical) albedo of the object in the telescope’s field of view, a number between zero and one.
• If you want to find the albedo of a specific light or dark part of the Moon, you will need to increase the magnifying power until only that part can be seen. You’ll have to do the same thing if more than one object is visible, because otherwise the telescope will average the albedos.
• Albedo is much harder to measure than angular size.
• First identifies a familiar celestial object (a planet or the Moon) from the magic it reflects.
• The object’s (average) distance from the Sun and measures its angular size, its phase, and the amount of light it reflects to Earth. Then it calculates the albedo from the formula below.
• Value it calculates is a good approximation only if the body is a familiar one.
• The orbit of the planet is nearly circular, and the phase isn’t a result of part of the light being blocked.
Interference and Magical Albedo
• To calculate the interference, you need to measure the angular separation between the object in question (the target) and each of the other objects in the sky, which can be estimated accurately enough from viewing angles.
• The relative strength of the magic reflected by each of the other bodies compared to the magic reflected by the target itself.
• To calculate the magical albedo from the optical albedo, you need to know what the surface is made of.
• The magical albedo of most surfaces is the same as the optical albedo.
• A rocky surface reflects only about half as much magic as light, and water, including ice, cuts the magical albedo in half again, as it tames and absorbs the Sun’s magic.
• You can calculate the amount of magic that an object reflects towards the Earth.
• The von Rheticus telescope has about as much resolving power as a 12-centimeter-wide Muggle-built telescope (about one arcsecond), but less than 1/20 the light-gathering power.
• Muggles have made so much more progress in technology.
• Their best telescopes are far superior to ours. This technology enables them to make measurements of angular size, phase, optical albedo, and distance from the Sun more accurately than we can. The 100-inch-wide Hubble telescope has 20 times as much resolving power as the von Rheticus model, and the ground-based Keck telescope uses adaptive optics to equal or even better Hubble’s resolving power despite the wobbling of the image caused by the movement of the air.
• The beam of light is a laser beam, which is used for the aforementioned adaptive optics. The movement of the air makes the beam and the nearby stars seem to wobble, but the primary mirror follows the beam and adjusts to it by bending just enough to cancel the wobbling of the beam, thus cancelling the apparent wobbling of the nearby stars as well.
Distance from the Sun
• Von Rheticus - The motion of planets in the sky and calculated the distance of each of the planets from the Sun.
• Telescope to be able to recognize a planet it was pointed at from the magic it reflected and entered into his telescope the distance of each of the planets from the Sun.
• Von Rheticus assumed that all the planets travel around the Sun in a circle.
• A planet’s distance from the Sun isn’t quite constant, because it revolves around the Sun in an ellipse, not a circle.
• The Sun isn’t in the middle of the ellipse. So, the distance he entered for each planet was the average one rather than the current one.
• Mars and Mercury are exceptions. A planet’s distance from the Sun at any specific time can be calculated exactly using a method discovered by Isaac Newton.
Angular Size, Phase and Optical Albedo
• Since Muggles can now find the optical albedo and angular size of these bodies more accurately than we can, we often use their values, presented in the table below, in our calculations.
• The Moon and some of the planets have lighter and darker parts with different specific albedos.
• You will notice that the albedo of each celestial body is constant, whereas its angular size depends upon how far the planet is from Earth. Which varies throughout the day, season, and year.
• Venus has the widest range of angular size, appearing about 6.8 times as large when it is closest to Earth as when it is farthest away.
• Button labelled “S” for Angular size. The angular size is shown in degrees, arcminutes and arcseconds.
• The word degrees are replaced by this symbol o, and standard notation is used for minutes and seconds.
• For example, if you’re looking at a comet, whose angular length is two degrees, 35 arcminutes, and 28 arcseconds, then, since a comet’s length is much greater than its width, you’ll see 2o35'28", whatever its width happens to be.
• Can always obtain the albedo and angular size of a body by consulting a table of values, as a magical person.
• Von Rheticus telescope has two additional buttons aside from the two zoom buttons and the focusing knob? If the telescope is held so that the focusing knob is on the left side, then those two buttons are situated on the top of the wider tube near the middle, where you might hold it to keep it balanced.
• Buttons is labelled “S” for angular size. When you press it, the angular size of the object, expressed in degrees, arcminutes, and arcseconds, appears at the bottom of the field of view in pure red characters.
• The word degrees is replaced by this symbol o, and standard notation is used for minutes and seconds.
• The von Rheticus telescope calculates the phase of an object by measuring its angular length and width and dividing the width by the length.
• Another button on your telescope is labelled “A”. A stands for albedo. The (optical) albedo of the object in the telescope’s field of view, a number between zero and one.
• If you want to find the albedo of a specific light or dark part of the Moon, you will need to increase the magnifying power until only that part can be seen. You’ll have to do the same thing if more than one object is visible, because otherwise the telescope will average the albedos.
• Albedo is much harder to measure than angular size.
• First identifies a familiar celestial object (a planet or the Moon) from the magic it reflects.
• The object’s (average) distance from the Sun and measures its angular size, its phase, and the amount of light it reflects to Earth. Then it calculates the albedo from the formula below.
• Value it calculates is a good approximation only if the body is a familiar one.
• The orbit of the planet is nearly circular, and the phase isn’t a result of part of the light being blocked.
Interference and Magical Albedo
• To calculate the interference, you need to measure the angular separation between the object in question (the target) and each of the other objects in the sky, which can be estimated accurately enough from viewing angles.
• The relative strength of the magic reflected by each of the other bodies compared to the magic reflected by the target itself.
• To calculate the magical albedo from the optical albedo, you need to know what the surface is made of.
• The magical albedo of most surfaces is the same as the optical albedo.
• A rocky surface reflects only about half as much magic as light, and water, including ice, cuts the magical albedo in half again, as it tames and absorbs the Sun’s magic.
• You can calculate the amount of magic that an object reflects towards the Earth.
