Telescopes OCR GCSE P7 21st century science

refracting telescopes use and objective lense and an eyepiece lense to collect paralell rays of light from stars the lenses must be the sum of the two focal lengths apart so you don't get a blurry image and they must be of differing strengths , the eyepiece being the stronger one of the two - if the lenses have little difference in their power then the telescope will not maginify an image very well if at all

this type of tellescope does not have an objective lense but instead it has a parabolic mirror / concave mirror which can be called the primary mirror this then focuses the rays of light on to a second mirror which channels the rays on to the eyepiece lense for us to see 

Advantages 

• you don't get blurry images due to the atmosphere or the weather 
• light pollution is not an issue 
• can see things in wave lengths that are normally absorbed by the earth's atmosphere such as x rays and infra red like the hubble space telescope
• you gain really good imagess - why not google hubble space telescope images ?

Disadvantages 

• high cost 
• hard to fix as they are so far away so you may have to send out people
• expensive to fix equpiment and space journeys too
• need a lot of expertise to make and design 
• litle conttrol over it