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AS101 (238)
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# Telescope notes I.docx

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Department
Astronomy
Course
AS101
Professor
Victor Arora
Semester
Fall

Description
Telescope notes I - Galileo did NOT invent the telescope - light changes direction when it interacts with matter - meaning the light is REFRACTED - Refracted: the bending of light when it is passing through a new medium - Ex: The refraction of light when it passes from a fast medium to a slow medium bends the light ray toward the normal to the boundary between the two media - Refraction depends on the wavelength of light and the lenses used causes the lights to bend more - refracting telescopes that use lenses to gather and focus light - reflecting telescopes that use mirrors - reflecting ones use a mirror as it is a SMOOTH surface - use the same angle; no bending of light - special property: parabolic mirrors take their incoming rays of light and converge it into one ray - refractive use primary lenses to bend the light and bring it to focus - BUT they are not the best BECAUSE … - The have chromatic abbreviation: different wavelengths are focused at different sections meaning the image is reliable as the light isn’t the same - Eyepiece is used to magnify inverted image reflective - primary mirror reflects the light back to a focus instead of refracting it - concave spherical or parabolic shape, and, as it reflects the light, it inverts the image at the focal plane. (just follow the arrows! They show how the same light is being bounced, same wavelength! But the eyepiece gets an inverted view) - telescopes are like buckets… THE LARGER THE MIRROR THE BRIGHTER THE IMAGE - LGP light gathering power is proportional to the primary lens - So a 2 meter primary lenses has 4 times the LGP - Telescope resolving : the size of the diffraction fringes is inversely proportional to diameter of the primary mirror doubling the size of the mirror means that I can resolve twice as well and is also proportional to wavelength if I observe at longer wavelengths, I will have poorer   resolution λ optional equation that describes this relationship:   ∆ θ=1.22 D   where ∆ θ is the angular separation of the fringes, λ is the wavelength and D is the diameter Eyepiece: - a smaller eyepiece gives a larger magnification - but the image will be dimmer (i.e. more spread out) - The magnification of a
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