THE VON RHETICUS MODEL TELESCOPE

• terrestrial instrument, things seen on the right side up in a wide field of view


• 2 buttons (big and small) on the eyepiece for adjusting the power of the telescope


• pressing the button => shows a red number (current magnification) at the edge of your field of view for 0.5 seconds, gradually changing it until you stop pressing the button
  
  
  
  • big button - increase
  
  
  • small button - decrease
  
  
  
  


• magnifying power: 10 - 250


• change of power requires a shift in focus


• sliding the eyepiece into and out of the objective lens tube = change of focus


• autofocus = sets focus on the nearest object in your field of view (the focusing knob must be pushed in)
  
  
  
  • to disable it, pull the knob out
  
  
  
  


• 15cm long, objective lens is 2.5cm wide


• resolution: the smallest angular distance between 2 points of light


• the wider the objective lens - the smaller the resolution


• resolution of 1 arcsecond (normal would have 5 arcseconds, but this is a magical telescope)


• light enough to hold in your hand
  
  
  
  • usual Muggle-built telescope (12.5cm wide) must be attached to a tripod
  
  
  
  


• lenses are fragile, easily scratched and broken
  
  
  
  • protection spells: - the Scratch-Resistant Charm
                                 - the Break-Resistant Charm
  
  
  
  


• a cap that fits over the objective lens is attached to the other tube by a string + the Sticking Charm to prevent the loss of the cap
  
  
  
  • good idea to write your name on it
  
  
  • always keep it on when not using the telescope
  
  
  
  


• banned to look at the Sun and the full Moon (enough magical power to destroy all the charms cast on the telescope)
  
  
  
  • if you want to look at the Sun, use a sun filter that is placed over the objective lens
  
  
  
  

THE LUNASCOPE

• a tube with a hole in one end to look through


• three buttons to set a day, month and year so you can see what phase it will be 

THE MOON CHART

• piece of parchment, there are ten consecutive dates side by side with a picture of a Moon phase over it


• tap on the right side of the parchment shows the next ten dates


• tap on the right side shows the previous ten ones

THE CELESTIAL GLOBE

• shows the stars and constellations in the sky + their names


• some globes show the mirror image, others show it normally, and some invert the image


• the magical model shows the Sun, the Moon, the planets and their names 
  
  
  
  • the Muggle one doesn't
  
  
  
  

OTHER ASTRONOMICAL TOOLS

• Orrery - a model of the solar system, where planets move around the Sun 
  
  
  
  • there's no scale to size (although the planets and the Sun are bigger than other celestial bodies)
  
  
  • there is a scale to the time it takes to revolve around the Sun - but it takes much less time
  
  
  • the celestial bodies float in the air 
    
    
    
    • in the Muggle version, planets are attached to the sun by metal rods and move thanks to an electrical motor
    
    
    
    
  
  
  
  


• Star Chart 
  
  
  
  • used by Muggles and wizards
  
  
  • a flat map of the sky that helps to locate stars and constellations
  
  
  • doesn't show planets
  
  
  
  


• Astronomer’s Lamp (red light)
  
  
  
  • reduces your dark adaptation less than white (which normally takes 30 minutes for your eyes to restore fully)
  
  
  • must be pure red without other colours in the light
  
  
  
  

VIEWING TIPS

• a telescopic sight - attached to the top of a Muggle telescope, helps to find/locate an object in the sky
  
  
  
  • if you don't have one, set the scope’s power to the lowest until you find what you want and set the power back up 
  
  
  
  


• to see dim stars: look away from the centre of the viewing field (in your eye, the middle of the retina called the fovea centralis is more sensitive to colour, has better resolution, and is less sensitive to dim light)


• stars twinkle (movement of the air), planets don't (larger angular size)
  
  
  
  • Betelgeuse (0.044 arcseconds) is a star with the biggest angular size
  
  
  • Neptune (2.2 arcseconds) is a planet with the smallest angular size
  
  
  
  


• this picture shows the (approximate) apparent angular size when you want to estimate how many degrees are two celestial bodies apart: