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Satellite TV receivers & systems support forums
DISH SETUP: Single sat, Multi-Sat & Motorised
C-Band Reception, UK and Europe
Disaster!!
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<blockquote data-quote="Huevos" data-source="post: 753357" data-attributes="member: 301161"><p>Yes... but if you are just putting the subreflector at the focal point you haven't changed the focal length at all. To change the focal length (to longer) you would need a shallower parabola. With a proper Cassagrain design there is no convergence between the primary and secondary reflector, nor at the secondary reflector. The first point of focus happens at the LNB (or eyepiece in the case of a telescope). This is in contrast to a Gregorian design where there is a focal point between the primary and secondary reflectors, and a second focal point at the LNB (or eyepiece in the case of a telescope).</p><p></p><p>_http://en.wikipedia.org/wiki/Cassegrain_reflector</p><p>_http://en.wikipedia.org/wiki/Gregorian_telescope</p></blockquote><p></p>
[QUOTE="Huevos, post: 753357, member: 301161"] Yes... but if you are just putting the subreflector at the focal point you haven't changed the focal length at all. To change the focal length (to longer) you would need a shallower parabola. With a proper Cassagrain design there is no convergence between the primary and secondary reflector, nor at the secondary reflector. The first point of focus happens at the LNB (or eyepiece in the case of a telescope). This is in contrast to a Gregorian design where there is a focal point between the primary and secondary reflectors, and a second focal point at the LNB (or eyepiece in the case of a telescope). _http://en.wikipedia.org/wiki/Cassegrain_reflector _http://en.wikipedia.org/wiki/Gregorian_telescope [/QUOTE]
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Satellite TV receivers & systems support forums
DISH SETUP: Single sat, Multi-Sat & Motorised
C-Band Reception, UK and Europe
Disaster!!
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