Astronomy Part 1( Specially for first and second years)
written by Account Terminated
Astronomy instructs students on planets, stars, and other sky objects and their role in the magical world. At Hogwarts, this may be a core subject, required of all Hogwarts students until at least their fifth year; those with sufficiently high O.W.L. marks in the course can then go on to N.E.W.T.-level study in years 6 and 7.
Last Updated
05/31/21
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Lesson 6: All about Telescope and Harry
Chapter 6
"Telescopes can be used for studying the night skies and identifying different stars and planets."
—Description[src]
A telescope is a device used for seeing faraway objects.[1] Those used in the wizarding world are presumably magical to some extent, as they can be used to see objects that would be impossible to see with a Muggle telescope.
They are essential in Astronomy, and thus all Hogwarts students up to their fifth year (and their sixth and seventh should they choose Astronomy as an elective) are required to own one.[2] Wiseacre's Wizarding Equipment sells brass telescopes for five Galleons.[3]
Weasleys' Wizard Wheezes sells a joke version of this product: the boxing telescope.[4]
MAGIC, a system of two imaging atmospheric Cherenkov telescopes, achieves its best performance under dark conditions, i.e. in absence of moonlight or twilight. Since operating the telescopes only during dark time would severely limit the duty cycle, observations are also performed when the Moon is present in the sky. Here we develop a dedicated Moon-adapted analysis to characterize the performance of MAGIC under moonlight. We evaluate energy threshold, angular resolution and sensitivity of MAGIC under different background light levels, based on Crab Nebula observations and tuned Monte Carlo simulations. This study includes observations taken under non-standard hardware configurations, such as reducing the camera photomultiplier tubes gain by a factor ~1.7 (Reduced HV settings) with respect to standard settings (Nominal HV) or using UV-pass filters to strongly reduce the amount of moonlight reaching the cameras of the telescopes. The Crab Nebula spectrum is correctly reconstructed in all the studied illumination levels, that reach up to 30 times brighter than under dark conditions. The main effect of moonlight is an increase in the analysis energy threshold and in the systematic uncertainties on the flux normalization. The sensitivity degradation is constrained to be below 10%, within 15-30% and between 60 and 80% for Nominal HV, Reduced HV and UV-pass filter observations, respectively. No worsening of the angular resolution was found. Thanks to observations during moonlight, the maximal duty cycle of MAGIC can be increased from ~18%, under dark nights only, to up to ~40% in total with only moderate performance degradation.
Within the Harry Potter stories are many scenes that can be analyzed astronomically. As both an astronomer and a teacher, these interest me, and so I will present such analysis here. My goal is not to criticize Rowling when she is inaccurate in her astronomy (or, for that matter, to praise her when she gets it right), because she is clearly not concerned with making her tales scientifically accurate—she’s writing a story, not an astronomy textbook.
“Mars is bright tonight,” Ronan repeated . . . . “Unusually bright.” (PS15)
As seen from Earth, Mars varies greatly in its apparent brightness, due to both the changing distance between the two planets, and the changing amounts of sunlit surface Mars presents to us. Roughly every 26 months, the Earth is closest to the red planet, and Mars looks brightest; at these times Mars is said to be in opposition.
However, according to the Lexicon Timeline, Ronan’s remark about Mars’s unusual brightness was made in late May of 1992, about 7.5 months before its January 1993 opposition. On that night in the Forbidden Forest, Mars was in fact only at about 10% of its maximum brightness[1]—hardly “unusually bright.”
[In Diagon Alley, Harry] was sorely tempted, too, by the perfect, moving model of the galaxy in a large glass ball, which would have meant he never had to take another Astronomy lesson. (PA4)
A perfect model of our Milky Way Galaxy—the enormous conglomeration of hundreds of billions of stars to which our Sun belongs—would be very cool indeed, but as Professor Sinistra’s class appears to focus only on our solar system (just the Sun, its planets, and their moons), it is hard to understand why this galactic model would be so helpful to Harry. If the glass ball containing the scaled-down Milky Way was three feet in diameter, our solar system would be an invisible speck within it, about a millionth of an inch in size. Perhaps, when Rowling was describing this item, she confused the terms “galaxy” and “solar system”—a common error.
“Did you check the lunar chart and realize that I was always ill at the full moon?” (PA17)
The average length of time from one full moon to the next is 29.53 days. Three dates when we know Lupin was ill are November 5, December 25, and June 6. However, since those dates are not multiples of 29.53 days apart, they cannot all have been full moons.[2]
“the hippogriff Buckbeak, hereafter called the condemned, shall be executed on the sixth of June at sundown” (PA21)
The time of that fateful sunset can be estimated by using the events in the story. At 11:55 PM that night, Harry and Hermione went back in time by three hours. They heard their earlier selves crossing the entrance hall with Ron and leaving for Hagrid’s cabin, walking slowly under the Invisibility Cloak (PA21). If it took the Trio fifteen minutes to cross the grounds, then they arrived at Hagrid’s at 9:10 PM. According to Lupin, they were in Hagrid’s hut for twenty minutes (PA17), and therefore left around 9:30 PM. The execution party arrived at the same time; they read the official notice, signed it, walked outside, and saw Buckbeak gone; then the executioner threw his axe (PA21). If all of that took five minutes, then the axe was thrown at approximately 9:35 PM. At that moment, “the very last rays of the setting sun were casting a bloody light over the long-shadowed grounds,” (PA17) so it was just before sundown.[3]
At first glance, this might seem like an unusually late sunset, but we must remember that (1) Britain is on Summer Time in June (what Americans call Daylight Saving Time), (2) the date is just before the summer solstice, the longest day of the year, and (3) Hogwarts is quite far to the north, in Scotland (according to this web site referenced by the Lexicon).
Mainland Scotland lies roughly at latitude 55-58º N and longitude 2-6º W. On June 6 in that region, sunset ranges between 9:40 PM and 10:20 PM British Summer Time[4], so the timing roughly agrees with Rowling’s chronology (the agreement gets worse the farther Hogwarts is to the north and west).
“Jupiter’s biggest moon is Ganymede, not Callisto,” [Hermione] said. . . . , “and it’s Io that’s got the volcanoes. . . . Europa’s covered in ice, not mice . . . .” (OP14)
This information about Jupiter’s four largest moons is indeed correct.
A twinkling red star winked at [Harry] from overhead. . . . “Mars, bringer of battle, shines brightly above us.” (OP27)
Mars does look like a red star to the naked eye, but since it is a planet, it does not appear to twinkle as the stars do. Also, the Lexicon Timeline estimates that Firenze’s first Divination class happened in early March of 1996, which was midway between Mars’s 1995 and 1997 oppositions. At that time, Mars was shining with only about 10% of its maximum brightness.[5]
Harry’s O.W.L. Astronomy practical (OP31)
In the discussion that follows, I will assume that this exam began at 11 PM British Summer Time[6] on June 24, 1996,[7] and lasted for 90 minutes.[8] I will also (somewhat arbitrarily) place Hogwarts about midway between Edinburgh and Aberdeen, at latitude 56.5º N, longitude 2.5º W. Using these parameters and the online interactive planetarium Your Sky (implemented by John Walker), I have generated maps showing which stars would have been visible in the sky at the beginning (Figure 1.) and end (Figure 2.) of the exam (the moon and the planets are not drawn, as they change their positions from year to year).
—Description[src]
A telescope is a device used for seeing faraway objects.[1] Those used in the wizarding world are presumably magical to some extent, as they can be used to see objects that would be impossible to see with a Muggle telescope.
They are essential in Astronomy, and thus all Hogwarts students up to their fifth year (and their sixth and seventh should they choose Astronomy as an elective) are required to own one.[2] Wiseacre's Wizarding Equipment sells brass telescopes for five Galleons.[3]
Weasleys' Wizard Wheezes sells a joke version of this product: the boxing telescope.[4]
MAGIC, a system of two imaging atmospheric Cherenkov telescopes, achieves its best performance under dark conditions, i.e. in absence of moonlight or twilight. Since operating the telescopes only during dark time would severely limit the duty cycle, observations are also performed when the Moon is present in the sky. Here we develop a dedicated Moon-adapted analysis to characterize the performance of MAGIC under moonlight. We evaluate energy threshold, angular resolution and sensitivity of MAGIC under different background light levels, based on Crab Nebula observations and tuned Monte Carlo simulations. This study includes observations taken under non-standard hardware configurations, such as reducing the camera photomultiplier tubes gain by a factor ~1.7 (Reduced HV settings) with respect to standard settings (Nominal HV) or using UV-pass filters to strongly reduce the amount of moonlight reaching the cameras of the telescopes. The Crab Nebula spectrum is correctly reconstructed in all the studied illumination levels, that reach up to 30 times brighter than under dark conditions. The main effect of moonlight is an increase in the analysis energy threshold and in the systematic uncertainties on the flux normalization. The sensitivity degradation is constrained to be below 10%, within 15-30% and between 60 and 80% for Nominal HV, Reduced HV and UV-pass filter observations, respectively. No worsening of the angular resolution was found. Thanks to observations during moonlight, the maximal duty cycle of MAGIC can be increased from ~18%, under dark nights only, to up to ~40% in total with only moderate performance degradation.
Within the Harry Potter stories are many scenes that can be analyzed astronomically. As both an astronomer and a teacher, these interest me, and so I will present such analysis here. My goal is not to criticize Rowling when she is inaccurate in her astronomy (or, for that matter, to praise her when she gets it right), because she is clearly not concerned with making her tales scientifically accurate—she’s writing a story, not an astronomy textbook.
“Mars is bright tonight,” Ronan repeated . . . . “Unusually bright.” (PS15)
As seen from Earth, Mars varies greatly in its apparent brightness, due to both the changing distance between the two planets, and the changing amounts of sunlit surface Mars presents to us. Roughly every 26 months, the Earth is closest to the red planet, and Mars looks brightest; at these times Mars is said to be in opposition.
However, according to the Lexicon Timeline, Ronan’s remark about Mars’s unusual brightness was made in late May of 1992, about 7.5 months before its January 1993 opposition. On that night in the Forbidden Forest, Mars was in fact only at about 10% of its maximum brightness[1]—hardly “unusually bright.”
[In Diagon Alley, Harry] was sorely tempted, too, by the perfect, moving model of the galaxy in a large glass ball, which would have meant he never had to take another Astronomy lesson. (PA4)
A perfect model of our Milky Way Galaxy—the enormous conglomeration of hundreds of billions of stars to which our Sun belongs—would be very cool indeed, but as Professor Sinistra’s class appears to focus only on our solar system (just the Sun, its planets, and their moons), it is hard to understand why this galactic model would be so helpful to Harry. If the glass ball containing the scaled-down Milky Way was three feet in diameter, our solar system would be an invisible speck within it, about a millionth of an inch in size. Perhaps, when Rowling was describing this item, she confused the terms “galaxy” and “solar system”—a common error.
“Did you check the lunar chart and realize that I was always ill at the full moon?” (PA17)
The average length of time from one full moon to the next is 29.53 days. Three dates when we know Lupin was ill are November 5, December 25, and June 6. However, since those dates are not multiples of 29.53 days apart, they cannot all have been full moons.[2]
“the hippogriff Buckbeak, hereafter called the condemned, shall be executed on the sixth of June at sundown” (PA21)
The time of that fateful sunset can be estimated by using the events in the story. At 11:55 PM that night, Harry and Hermione went back in time by three hours. They heard their earlier selves crossing the entrance hall with Ron and leaving for Hagrid’s cabin, walking slowly under the Invisibility Cloak (PA21). If it took the Trio fifteen minutes to cross the grounds, then they arrived at Hagrid’s at 9:10 PM. According to Lupin, they were in Hagrid’s hut for twenty minutes (PA17), and therefore left around 9:30 PM. The execution party arrived at the same time; they read the official notice, signed it, walked outside, and saw Buckbeak gone; then the executioner threw his axe (PA21). If all of that took five minutes, then the axe was thrown at approximately 9:35 PM. At that moment, “the very last rays of the setting sun were casting a bloody light over the long-shadowed grounds,” (PA17) so it was just before sundown.[3]
At first glance, this might seem like an unusually late sunset, but we must remember that (1) Britain is on Summer Time in June (what Americans call Daylight Saving Time), (2) the date is just before the summer solstice, the longest day of the year, and (3) Hogwarts is quite far to the north, in Scotland (according to this web site referenced by the Lexicon).
Mainland Scotland lies roughly at latitude 55-58º N and longitude 2-6º W. On June 6 in that region, sunset ranges between 9:40 PM and 10:20 PM British Summer Time[4], so the timing roughly agrees with Rowling’s chronology (the agreement gets worse the farther Hogwarts is to the north and west).
“Jupiter’s biggest moon is Ganymede, not Callisto,” [Hermione] said. . . . , “and it’s Io that’s got the volcanoes. . . . Europa’s covered in ice, not mice . . . .” (OP14)
This information about Jupiter’s four largest moons is indeed correct.
A twinkling red star winked at [Harry] from overhead. . . . “Mars, bringer of battle, shines brightly above us.” (OP27)
Mars does look like a red star to the naked eye, but since it is a planet, it does not appear to twinkle as the stars do. Also, the Lexicon Timeline estimates that Firenze’s first Divination class happened in early March of 1996, which was midway between Mars’s 1995 and 1997 oppositions. At that time, Mars was shining with only about 10% of its maximum brightness.[5]
Harry’s O.W.L. Astronomy practical (OP31)
In the discussion that follows, I will assume that this exam began at 11 PM British Summer Time[6] on June 24, 1996,[7] and lasted for 90 minutes.[8] I will also (somewhat arbitrarily) place Hogwarts about midway between Edinburgh and Aberdeen, at latitude 56.5º N, longitude 2.5º W. Using these parameters and the online interactive planetarium Your Sky (implemented by John Walker), I have generated maps showing which stars would have been visible in the sky at the beginning (Figure 1.) and end (Figure 2.) of the exam (the moon and the planets are not drawn, as they change their positions from year to year).
