A perfectly aligned and aberration free optics should image a star as a diffraction limited pattern (Airy’s disk) at the scope focal plane. This is an important point, on which one shall return later onįor the time being let’s assume that the starlight is a plane wave indeed when reaching a telescope aperture. However this is a random process, which averages out overtime, therefore long term analyses deal essentially with plane waves too. The atmospheric turbulence (seeing) distorts the wavefront. For many years the starlight travels without any perturbation in the space before reaching the Earth’s atmosphere.Īt the top of our atmosphere the starlight wavefront is a plane wave.Īlthough if the last 20km takes only 66 micro-seconds, they have a significant impact on the instantaneous wavefront shape. ![]() Stars are far away and can be seen as punctual sources. Shack-Hartmann analyzer: Theory of operation The second row shows the Shack Hartmann wavefront modal reconstructions, color coded (red for maximum, blue for minimum phase error). Then for a 70 nm rms wave aberration (l/8) due to: (2) coma only, (3) astigmatism only, and (4) spherical only. However wavefront analysis provides a precise quantitative evaluation of the all optical system and related aberrations, even under a less than optimal seeing.īelow, first row from left to right, the point spread function (PSF) of: (1) a perfect diffraction limited scope. It is a necessary, but not sufficient condition. But as we shall see below even if the rings are eventually made concentric, this is not in any way, an indication of a good collimation, or optics. The “star test” is looking for such asymmetries. A gross optical element misalignment result typically in on-axis coma, which skews and offsets the otherwise concentric diffraction rings surrounding a star. The popular and traditional “star test”, looking at the Airy disk shape, is quite limited by seeing and more importantly by the type of aberration which can be revealed with such simple technique. Optimal guiding Excel calculator download. ![]() StarWave wavefront analyzer documentation & tutorial.SkyGuide/Guard, SkyWave documentation & tutorial.ONAG & accessories documentation & tutorial.TeamViewer Customer Support Module Download. ![]() ON Axis Guider – How does an ONAG work?.Telescope collimation using AI based wavefront sensing SkyWave mathematical models for telescopes & PPU credit reloads.SkyGuide, SkyGuard (SKG) & SkyWave (SKW).
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