![]() The small wavy modulations are errors which originate either from a lens distortion error (Polaris was not centered in the field of view) or improper centering. Star trails flatten and become identical in length, however (Over-plotted a spherical coordinate system to better track the coordinate transformation in the next step). Create an animation of what the sky would look like in real time, the stars will wink out whenever they are obscured by a small cloud.īy playing the animation at a suitable speed, the cloud motions and positions should be obvious.Then subtracting the star trail for it, then repeating with the next fainter star, until all the stars have been analyzed. Use the star positions to begin recovery of the temporal light curve for each star by starting with the brightest star,.Determine the coordinates of all the stars in the deconvolved image.Deconvolve the star trails using uniform horizontal motion blurring software in Right Ascension only (phi or x-axis).Detect left edge discontinuities in each pixel row and provisionally assign a star position or.Un-smear the star images in spherical coordinates with special consideration of the cyclic boundary conditions on the left and right borders (phi=0 and 360).When using a star coordinate database skip to step 9.Star trail length must beĬonstant in spherical coordinates because they subtend equal angular displacements (common sense really). If the length of star trails are not a constant then redo step 3 until they are. Determine the total arc length of star trails.Star trails must be perfectly linear horizontal streaks in spherical coordinates. If the star trails show any curvature redo step 3.Using Photoshop CS2 Filter/Distort/Polar Coordinates/Polar to Rectangular or.Map the image to spherical coordinate theta (Declination) and phi (Right Ascension),įlattening the star trails and making them all of equal length.Locate celestial pole or Polaris, if absent extrapolate.Obtain a star trail image(s) : The Flickr Star Trail pool is a good source.The output of the program is a series of polynomial coefficients which can be plugged into Photoshop distortion correction software or plugins. Size of the camera and because star positions are highly accurate (except for atmospheric refraction). ![]() The program can be used to model and eliminate lens distortion because the stars are at 'infinity' relative to the small Of course this could be done in a much easier way by taking hundreds of short exposures,īut I like challenges. ![]() Is to reconstruct the motion of small clouds by analyzing the luminosity versus time behavior of the brighter star trails. Small clouds passing in front of these stars are attenuating the light. In star trail photos there are often small notches in the star trails when viewed at high resolution. Star Trail Analysis Software by John Talbot ![]()
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