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
915
Lesson Three
Chapter 3
Von Rheticus Model Telescope
• Von Rheticus Model Telescope, a terrestrial instrument, so you see things right side up in a wide field of view when you use it.
• Features of the von Rheticus Model Telescope buttons to adjust the power. A knob to change the focus. Autofocus to focus on objects nearest in the field of view, when the know is pushed in.
• There are two buttons, a bigger one and a smaller one, located on the eyepiece, for adjusting the power of the telescope. Current magnification as a red number.
• The bigger one increases it by moving the outer eyepiece lens farther away from the inner one, and the smaller one decreases it by moving the outer eyepiece lens nearer to the inner one.
• The magnifying power ranges from a minimum of 10 to a maximum of 250. Changing the power generally requires changing the focus.
• There is a knob on the left side of the wider tube near the eyepiece that changes the focus by sliding the eyepiece tube into and out of the objective lens tube.
• Autofocus, which focuses on the nearest object in your field of view as long as the focusing knob is pushed in.
• The von Rheticus telescope is small enough to fit into your pocket: it’s about 15 centimetre’s long and the objective lens is about 2.5 centimetre’s.
• The resolution of a telescope is the smallest angular distance between two points of light.
• The wider the objective lens of a Muggle-built telescope is, the smaller the resolution will be.
• A Muggle-built telescope with a 2.5-centimeter-wide objective lens has at best a resolution of about five arcseconds.
• Your telescope would have to be at least 12.5 centimetres wide to achieve a resolution of one arcsecond. The von Rheticus model can achieve a resolution of one arcsecond, even with an objective lens only 2.5 centimetre’s wide. The greatest useful magnifying power of the von Rheticus telescope is about 250, which is why that’s its maximum power
• The greatest magnifying power of a telescope that is useful is about 250 divided by the resolution in arcseconds.
• There are two charms that protect the objective lens: The Scratch-Resistant Charm and the Break-Resistant Charm. It’s harder to scratch or break the lens than it would be without those charms.
• The Sticking Charm, which prevents the cap from getting lost.
• Treat your telescope the way you would treat any fragile and precious thing – with appropriate care.
• There are two celestial bodies that you mustn’t look at through your magical telescope: The Sun and the full Moon. Magical power to destroy all the charms that were cast on your telescope.
• Looking at the Sun through any telescope will instantly blind you in one eye unless you use a sun filter.
• The lens cap will protect the lens against accidental breaking or scratching and also against the light of the Sun or the full Moon hitting it.
The Lunascope and the Moon Chart
• You would be unable to use your von Rheticus telescope, and even Moon viewing would be at its worst due to the absence of shadows cast by the mountains and the rims of craters.
• Lunascope - it looks like a telescope because it’s a tube with a hole in one end to look through. You punch the day, month, and year into the three buttons on the side of the tube and look through the hole; then you will see a picture of the Moon in the phase it will be in on the day you have chosen.
• Moonchart - piece of parchment that shows ten consecutive dates side by side, over each of which is a picture of the Moon in the phase it will be in on that date.
• Touching a spot on the right side of the parchment makes it show the next ten dates and touching a spot on the left side makes it show the previous ten dates. It’s less expensive than a lunascope, but it takes longer to turn to a date in the distant future.
The Celestial Globe
• A celestial globe is like a terrestrial one except that instead of showing the countries and oceans on the surface of the Earth, it shows the stars and constellations in the sky, as well as the names of some of those stars and constellations.
• Other globes invert the image so that the constellations appear the same way as they do from Earth.
• Useful astronomical tool muggle version can’t show the sun, the moon or the planets, as they move in respect of the stars.
• The magical version of the celestial globe does show the Sun, Moon, and planets and their names, and you can even make it show where they were or will be on any given day. This makes it easier to locate the planets in the sky, and it is also a valuable tool for astrology.
Other Astronomical Tools
• Orrery, model of the solar system, with the planets moving around the Sun.
• This is not to scale.
• Muggle-built version, the planets are attached to the sun by metal rods and made to move by electrical motors.
• Magical version, the sun and the planets float in the air and are enchanted to move
• This tool is used mainly for educational rather than research purposes.
• Star chart, flat map of the sky with no magical properties. Helps you locate stars and constellations in the sky.
• Astronomer’s lamp. emits a pure red light whose brightness you can control so that you can choose the dimmest light that still enables you to do what you want to do. When reading a star chart without diminishing your dark adaption in the eye you’ll be using to look through your telescope: close that eye while the astronomer’s lamp is on!
Viewing Tips
• Do not try to locate an object with your telescope set to high power, because otherwise you will see so little of the sky that it would be hard to even find the Moon.
• Your telescope may have better resolution than a Muggle-built telescope of the same size, but it doesn’t gather any more light.
• You look away from the centre of the viewing field, a star may pop into view. This is because the middle of your eye, or rather, the middle of the retina called the fovea centralis, although it is more sensitive to colour and has better resolution than any other part of the eye, is less sensitive to dim light than the other parts.
• The fovea centralis consists of colour-sensitive cones, whereas the periphery of the retina consists of colour-blind but more light-sensitive rods.
• Stars twinkle because of the movement of the air. Planets don’t twinkle because they have a larger angular size.
• The star with the biggest angular size is Betelgeuse (0.044 arcseconds), whereas the planet with the smallest angular size is Neptune (2.2 arcseconds at the minimum).
• You want to estimate how many degrees two celestial bodies are apart. There’s an easy way to do so which requires no magic at all. Hold your hand out at arm’s length and compare the apparent distance between the two celestial objects with the apparent size of a part of your hand.
• Von Rheticus Model Telescope, a terrestrial instrument, so you see things right side up in a wide field of view when you use it.
• Features of the von Rheticus Model Telescope buttons to adjust the power. A knob to change the focus. Autofocus to focus on objects nearest in the field of view, when the know is pushed in.
• There are two buttons, a bigger one and a smaller one, located on the eyepiece, for adjusting the power of the telescope. Current magnification as a red number.
• The bigger one increases it by moving the outer eyepiece lens farther away from the inner one, and the smaller one decreases it by moving the outer eyepiece lens nearer to the inner one.
• The magnifying power ranges from a minimum of 10 to a maximum of 250. Changing the power generally requires changing the focus.
• There is a knob on the left side of the wider tube near the eyepiece that changes the focus by sliding the eyepiece tube into and out of the objective lens tube.
• Autofocus, which focuses on the nearest object in your field of view as long as the focusing knob is pushed in.
• The von Rheticus telescope is small enough to fit into your pocket: it’s about 15 centimetre’s long and the objective lens is about 2.5 centimetre’s.
• The resolution of a telescope is the smallest angular distance between two points of light.
• The wider the objective lens of a Muggle-built telescope is, the smaller the resolution will be.
• A Muggle-built telescope with a 2.5-centimeter-wide objective lens has at best a resolution of about five arcseconds.
• Your telescope would have to be at least 12.5 centimetres wide to achieve a resolution of one arcsecond. The von Rheticus model can achieve a resolution of one arcsecond, even with an objective lens only 2.5 centimetre’s wide. The greatest useful magnifying power of the von Rheticus telescope is about 250, which is why that’s its maximum power
• The greatest magnifying power of a telescope that is useful is about 250 divided by the resolution in arcseconds.
• There are two charms that protect the objective lens: The Scratch-Resistant Charm and the Break-Resistant Charm. It’s harder to scratch or break the lens than it would be without those charms.
• The Sticking Charm, which prevents the cap from getting lost.
• Treat your telescope the way you would treat any fragile and precious thing – with appropriate care.
• There are two celestial bodies that you mustn’t look at through your magical telescope: The Sun and the full Moon. Magical power to destroy all the charms that were cast on your telescope.
• Looking at the Sun through any telescope will instantly blind you in one eye unless you use a sun filter.
• The lens cap will protect the lens against accidental breaking or scratching and also against the light of the Sun or the full Moon hitting it.
The Lunascope and the Moon Chart
• You would be unable to use your von Rheticus telescope, and even Moon viewing would be at its worst due to the absence of shadows cast by the mountains and the rims of craters.
• Lunascope - it looks like a telescope because it’s a tube with a hole in one end to look through. You punch the day, month, and year into the three buttons on the side of the tube and look through the hole; then you will see a picture of the Moon in the phase it will be in on the day you have chosen.
• Moonchart - piece of parchment that shows ten consecutive dates side by side, over each of which is a picture of the Moon in the phase it will be in on that date.
• Touching a spot on the right side of the parchment makes it show the next ten dates and touching a spot on the left side makes it show the previous ten dates. It’s less expensive than a lunascope, but it takes longer to turn to a date in the distant future.
The Celestial Globe
• A celestial globe is like a terrestrial one except that instead of showing the countries and oceans on the surface of the Earth, it shows the stars and constellations in the sky, as well as the names of some of those stars and constellations.
• Other globes invert the image so that the constellations appear the same way as they do from Earth.
• Useful astronomical tool muggle version can’t show the sun, the moon or the planets, as they move in respect of the stars.
• The magical version of the celestial globe does show the Sun, Moon, and planets and their names, and you can even make it show where they were or will be on any given day. This makes it easier to locate the planets in the sky, and it is also a valuable tool for astrology.
Other Astronomical Tools
• Orrery, model of the solar system, with the planets moving around the Sun.
• This is not to scale.
• Muggle-built version, the planets are attached to the sun by metal rods and made to move by electrical motors.
• Magical version, the sun and the planets float in the air and are enchanted to move
• This tool is used mainly for educational rather than research purposes.
• Star chart, flat map of the sky with no magical properties. Helps you locate stars and constellations in the sky.
• Astronomer’s lamp. emits a pure red light whose brightness you can control so that you can choose the dimmest light that still enables you to do what you want to do. When reading a star chart without diminishing your dark adaption in the eye you’ll be using to look through your telescope: close that eye while the astronomer’s lamp is on!
Viewing Tips
• Do not try to locate an object with your telescope set to high power, because otherwise you will see so little of the sky that it would be hard to even find the Moon.
• Your telescope may have better resolution than a Muggle-built telescope of the same size, but it doesn’t gather any more light.
• You look away from the centre of the viewing field, a star may pop into view. This is because the middle of your eye, or rather, the middle of the retina called the fovea centralis, although it is more sensitive to colour and has better resolution than any other part of the eye, is less sensitive to dim light than the other parts.
• The fovea centralis consists of colour-sensitive cones, whereas the periphery of the retina consists of colour-blind but more light-sensitive rods.
• Stars twinkle because of the movement of the air. Planets don’t twinkle because they have a larger angular size.
• The star with the biggest angular size is Betelgeuse (0.044 arcseconds), whereas the planet with the smallest angular size is Neptune (2.2 arcseconds at the minimum).
• You want to estimate how many degrees two celestial bodies are apart. There’s an easy way to do so which requires no magic at all. Hold your hand out at arm’s length and compare the apparent distance between the two celestial objects with the apparent size of a part of your hand.
