![]() #DIFFRACTION SPIKES PLUS#O’Reilly members experience live online training, plus books, videos, and digital content from nearly 200 publishers. Note the eight points this is caused by the 18-70mm DX having 8 aperture blades. Get Astronomy Hacks now with the O’Reilly learning platform. English: Diffraction spikes (sunstars) at f/8. They have a secondary mirror in the light path. The big Newtonian reflectors and SCTs provide a lot of aperture, but they are obstructed scopes. So why would anyone pay so much for such a small scope? In a word, image quality. Even a small apochromatic refractor can easily cost $2,000 or more without a mount. And those refractors, small as they are, aren’t cheap. But mixed in with these mid-size and large scopes, you’ll see a fair number of people using 3” to 5” premium apochromatic refractors, such as those made by Tele Vue, Takahashi, and TMB. There’ll also be a lot of people using 8”, 10”, and 12” SCTs. There’ll be a lot of people using Dobs up to 20” or larger. They provide a lot of decent-quality aperture for not much money.īut if you attend a large star party, you’ll see something puzzling. That’s the reason Newtonian reflectors, particularly Dobsonians, are so popular. The only way to remove them is to reduce exposure time, but for deep space astrophotography where this often isn't practical and you have very bright stars, people will resort to replacing the spider with one that's curved, where the spikes are basically non-existant. They're more prominent on brighter targets. Assuming the larger scope has at least decent optics, you can simply see more with a larger scope than with a smaller one, period. Diffraction spikes are caused by the spider holding the secondary mirror. A larger aperture gathers more light and provides higher resolution of fine detail. The brighter the light, the more prominent the. There’s an old saying among astronomers: Aperture Rules. Those are diffraction spikes, and if you look closely, you’ll see that all bright objects in the JWST images have the same eight-pointed pattern. But a simple, cheap hack can let your inexpensive Dob provide most of the benefits of an expensive apo refractor. Eliminate Diffraction Spikes and Increase Contrastīuild a $0 aperture mask to turn your $500 Dob into a $2,000 apo refractor. ![]()
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