THE VON RHETICUS MODEL TELESCOPE:

• A variety of Muggle-made tools are used by witches and wizards in regards to observational astronomy, some modified by magic. The most important of these modified tools is the magical telescope, with inclusion of the von Rheticus model telescope.


• This terrestrial instrument is around 15 centimetres long with an objective lens width of 2.5 centimetres. Despite these miniscule dimensions, the resolution of this telescope is just as efficient as a much larger Muggle-designed telescope.


• The von Rheticus telescope enables the view to be seen right side up in a particularly wide viewing field.


• A large and small button are located on the eyepiece of this design, allowing the power to be easily adjusted. The bigger button increases the telescope's magnification through moving the outer eyepiece lens further away from the inner eyepiece lens. In contrast, the smaller button decreases the telescope's magnification through moving the outer eyepiece lens nearer to the inner eyepiece lens.


• The current magnification is displayed as a red number at the edge of the field of view for half a second upon the press of either button, gradually changing until pressure on the button is released.


• The magnifying power of the von Rheticus telescope ranges between 10 and 250, and changing the focus is generally necessary when attempting to alter this. The knob on the left side of the wider tube near the eyepiece changes the focus of the telescope, sliding the eyepiece tube into and out of the objective lens tube.


• Autofocus allows the focus to quickly concentrate on the nearest object in the viewing field. This feature is enabled as long as pressure is exerted upon the focusing knob.


• Despite the various advantages regarding this feature, the nearest object within the field of view may not be of interest. Additionally, autofocus only correctly focuses if the user is neither short-shorted nor far-sighted.

RESOLUTION:

• The resolution of a Muggle-built telescope will decrease upon increasing the width of the objective lens.


• A Muggle-built telescope with an objective lens width of 2.5 centimetres will possess a resolution of five arcseconds at most.


• Uranus and Neptune always appear smaller than five arcseconds, so emerge as points of light instead of a disc.


• To achieve a resolution of one arcsecond, an objective lens width of at least 12.5 would be required. However, the von Rheticus telescope can achieve this resolution with an objective lens width of 2.5 centimetres, attainable through the utilisation of magic.


• The greatest magnifying power of a telescope is about 250 divided by the resolution in arcseconds, or about 20 times the objective lens width of a Muggle-built telescope. Increasing the magnifying power beyond this quantity causes distant objects to appear larger, but doesn't affect the resolution.


• The greatest useful magnifying power of the von Rheticus telescope is around 250.
  

MOVEMENT COMPENSATION:

• Muggle-built telescopes with a width of around 12.5 centimetres are not able to be used without the support of a tripod, as the heaviness of the telescope would cause uncontrollable shaking of the hands.


• Despite the insubstantial weight of the von Rheticus telescope, shaking would still be an obvious issue due to the reactions within the human nervous system. However, magic enables the telescope tube to detect this movement and compensate for it. 


• Adaptive optics can't compensate for air movement through the use of a von Rheticus telescope, hence why the greatest useful magnifying power is placed at 250.

LENS PROTECTION:

• Telescope lenses can be easily scratched or broken.


• The objective lens of a telescope can be protected through the utilisation of the Scratch-Resistant Charm and the Break-Resistant Charm. The Repairing Charm can be cast upon any damaged telescope, as the mentioned charms only partly limit these occurrences.


• The objective lens of a telescope is protected with a fitted cap. This cap is attached to a string that connects the cap to the tube through the utilisation of the Sticking Charm.


• Any charms cast on a telescope can be destroyed with the magical power of the Sun and the full Moon. In result, these are the two celestial bodies that mustn't be identified through a telescope.


• Additionally, looking at the Sun through any telescope has the ability to immediately blind the user in one eye unless a sun filter is positioned over the objective lens.

THE LUNASCOPE:

• A lunascope has the ability to provide information regarding what phase the Moon will be in at a future date.


• This tool consists of a tube with a hole in one end to look through. On the side of this tube, there are three individual buttons that are used to input the day, month, and year.


• Depending on the chosen day, the Moon in the phase it will be in will appear upon looking through the hole.

THE MOON CHART:

• A Moon chart is a piece of parchment that displays ten consecutive dates side by side. A picture of the Moon in the phase it will be in will appear over each of these individual dates. Through the inclusion of magic, the next ten dates will appear upon touching the right side of the parchment, while the previous ten dates will appear upon touching the left side of the parchment.


• A Moon chart is cheaper than a lunascope but takes a longer amount of time to identify a date in the distant future or past.

THE CELESTIAL GLOBE:

• A terrestrial globe shows the countries and oceans on the surface of Earth, as well as their names.


• In contrast, a celestial globe shows the stars and constellations in the sky, as well as a selection of their names.


• Some celestial globes appear to mirror the constellations, as looking up at the sky from the Earth's surface corresponds to viewing the inside of the globe, instead of the outside. Other globes invert the image, meaning that the constellations are depicted the same way as they do from the Earth's surface.


• In regards to the Muggle-built version, the celestial globe can't show the Sun, the Moon, or the planets due to the fact that these features are constantly moving.


• However, the magical version of the celestial globe does show the Sun, the Moon, and the planets, as well as their names. In addition, it is possible to identify the position of a particular celestial object on a specifically chosen day.

THE ORRERY:

• An orrery is disproportionate model of the solar system including the planets revolving around the Sun.


• The time taken by the planets to fully rotate around the Sun are to scale, but are immensely shorter within the model than they are within space, otherwise the motion of the fastest planet (Mercury) would appear unnoticeable.


• In regards to the Muggle-built version, metal rods connect to the planets and are forced to rotate through the utilisation of electrical motors.


• However, the magical version uses enchantments to enable the Sun and the planets to float and rotate in the air.

THE STAR CHART:

• A star chart is a flat map of the sky with no magical properties and helps identify stars and constellations in the sky.


• This is less heavy than a celestial globe, so is sufficent for carrying around when stargazing.

THE ASTRONOMER'S LAMP:

• An astronomer's lamp emits a pure red light that can be adjusted in brightness and provides a reliable source of light to read by.


• Exposure to bright light has the ability to ruin the eyes' adaptation in regards to the darkness, taking around half an hour to completely restore. However, pure red light reduces this dark adaptation less than white light.


• A brighter light is required to analyse a star chart, so closing the eye used to look through the telescope while the astronomer's lamp is being used will further reduce this dark adaptation.

VIEWING TIPS:

• Locating an object through a telescope with a high magnifying power will provide a highly miniscule field of view, establishing a challenge regarding the identification of any celestial object.


• A selection of Muggle-built telescopes possess an additional telescope (pointing in the same direction) attached to the top of the tube, known as a telescopic sight. This is used by astronomers to identify a particular object before viewing it through the eyepiece.


• Looking away from the centre of the field of view, a star may appear that couldn't be viewed otherwise. This is because the middle of the retina (the fovea centralis) is less sensitive to dim light than the other parts of the eye. 


• Due to the movement of the air, stars appear to sparkle when viewed from the surface of the Earth, unlike planets. This is because stars have a smaller angular size than planets.


• Rough estimates can be made regarding how many degrees two celestial bodies are apart through the apparent size of a hand.

TERMINOLOGY:

• The term resolution is dependent on the observed distance of two points of light, while still being seen as individual points. This is measured as an angle, not a straight-line distance.