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Dawes Limit
0.5800 arcsec
Dawes Limit vs Aperture Diameter
公式
## Telescope Image Resolution The resolving power of a telescope is limited by diffraction at the aperture. ### Dawes Limit **theta = 116 / D** where D is in mm. This empirical limit gives the smallest angular separation at which two equal stars can be distinguished. ### Rayleigh Criterion **theta = 1.22 * lambda / D** At 550 nm this is 138.4 / D arcseconds.
计算示例
200 mm aperture telescope.
- 01Dawes limit = 116 / 200 = 0.58 arcsec
- 02Rayleigh limit = 138.4 / 200 = 0.692 arcsec
常见问题
Does atmospheric seeing limit resolution?
Yes. At most sites, seeing limits resolution to about 1 to 3 arcseconds, regardless of aperture. Adaptive optics or space telescopes can overcome this.
What is the difference between Dawes and Rayleigh limits?
The Dawes limit is an empirical rule for equal-brightness star pairs. The Rayleigh criterion is a theoretical diffraction limit. Dawes is slightly more optimistic.
Does magnification affect resolution?
No. Magnification enlarges the image but cannot reveal detail beyond the diffraction limit. Over-magnifying just makes a blurry image bigger.