The 'Newtonian' reflecting telescope:
Invented by Sir Isaac Newton, English mathematician & physicist, January 4th, 1643. (well before the Dobson mount )....... and this optical tube assembly (OTA) is perhaps one of the most popular and widely used reflecting telescope. A great favourite of ATM's (Amateur Telescope Makers), the main mirror is either formed as a spherical or paraboloidal surface depending on focal length used. It can be made from a variety of materials, glass being the most frequently used by ATM's. An elliptical diagonal (flat ) placed at 45 degrees locates the image outside the tube where it can be accessed with an eyepiece or camera. All too often this optical tube assembly is mistakenly referred to as a 'Dobsonian' telescope because of the simple box-like alt/azimuth mount designed in very recent times by John Dobson. Newcomers are often misled into thinking there are two distinct telescopes. Traditionally, a Newtonian reflector has been mounted on a wide variety of alt/azimuth mounts for easy visual use, or on a more complex equatorial mount and used photographically. Sadly, in both instances, Newton's great invention is referred to variously as: a newt, a Dob, a dob. This mis-naming often leads newcomers to think there are two different telescopes a Newtonian & a 'Dobsonian'. John Dobson popularised the Newtonian reflector by using it on his simple box-like alt/az mount.
The more complicated truss tube Newtonian reflectors on their low profile bases, often motorised & fitted with drives and setting circles - are also mistakenly referred to as Dobsonian telescopes.
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Peltier Device.
What does “Peltier” mean?
Named after Jean Peltier, who discovered the thermoelectric cooling effect in 1834. Thermoelectric cooler, or TEC, is a descriptive term even though they also heat.
What does it do?
Used in many laboratory instruments for small heating and/or cooling applications. Also for cooling astronomy CCD cameras.
Theory
The principle behind thermoelectric devices was first discovered in 1821 by Thomas Seebeck. He observed that if a closed circuit was made from two dissimilar metals, an electric current flowed when the junctions were maintained at different temperatures. The reverse of this – application of a DC voltage to a closed circuit comprising dissimilar metals gives rise to a temperature change at the junction of the dissimilar metals. Modern cells use semiconductors, usually Bismuth Telluride.
To read the rest of this very informative article, courtesy of Flinders University, School of Medicine, please follow this link: Peltier Device
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Barlow lens.
Invented by English mathematician & engineer, Peter Barlow, Norwich on October 13, 1776.
... to be continued...
Information courtesy of: http://people.clarkson.edu/~ekatz/scientists/barlow.html