![]() ![]() ![]() That sounds like a lot of work and waste to get rid of diffraction spikes. I'm not sure if they did over 4 times the primary mirror grinding just to use an off-axis circle-ellipse that's less than a quarter the area of the mirror. They've been built by hobbyist astronomers (even with truss tubes holding the secondary/eyepiece section and a "tube" made out of cloth to block stray light). Yes that does seem like the best possible scope design. Perhaps if relative costs for these telescopes come down in the future, they will be more common. I am not saying that stray light or diffraction effects are never a problem, just that this is not a top problem and, if we need to trade down in size at all for an off-axis design, most astronomers would not accept it. If a nearby star is producing a bothersome diffraction spike, one can usually rotate the field to avoid this. ![]() Galaxies are not bright enough to produce diffraction patterns and the issue of stray light from nearby bright objects is far less of a problem than the foreground stars, zodiacal light, and night sky light actually in the line of sight. There is additional strain required to rotate and support an asymmetric structure like this, i.e. Diffraction spikes professional#The total weight of optics and supporting structures of professional telescopes can be many tons. The extra mechanical costs may be greater than the extra costs for the optics. However, for most astronomical work the additional costs are just not worth it, yet. Off-axis is particularly helpful in solar observations because it reduces stray light and eliminates a rotating diffraction pattern which can be severe when the sun is the target. There is a 1.6 meter off-axis telescope for solar observation at Big Bear Observatory called the New Solar Telescope (NST). ![]()
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