Carey mask
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A Carey mask is a focusing aid for astronomical telescopes. The mask is in the form of a thin card or sheet that is placed over the front aperture of the telescope. There are four series of slits in t
Focussing
Focussing neg
Detail of focus
Telescope
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A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally, it was an optical instrument using lenses, curved mirrors
The 100-inch (2.5 m) Hooker reflecting telescope at Mount Wilson Observatory near Los Angeles, used by Edwin Hubble to measure galaxy redshifts and discover the general expansion of the universe.
Replica of possibly the oldest surviving telescope (1609–1640), suspected to be an early "Cannocchiali" refracting telescope by Galileo Galilei.
A replica of a second reflecting telescope Isaac Newton presented to the Royal Society in London in 1672
Three radio telescopes belonging to the Atacama Large Millimeter Array