astrometry Package¶
trackSmooth
Module¶
oscaar v2.0 Module for differential photometry Developed by Brett Morris, 2011-2013
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oscaar.astrometry.trackSmooth.
quadraticFit
(derivative, ext)[source]¶ Find an extremum in the data and use it and the points on either side, fit a quadratic function to the three points, and return the x-position of the apex of the best-fit parabola.
Called by oscaar.trackSmooth()
Parameters: derivative : numpy.ndarray
The first derivative of the series of points, usually calculated by np.diff()
ext : string
Extremum to look find. May be either “max” or “min”
Returns: extremum : float
The (non-integer) index where the extremum was found
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oscaar.astrometry.trackSmooth.
trackSmooth
(image, est_x, est_y, smoothingConst, plottingThings, preCropped=False, zoom=20.0, plots=False)[source]¶ Method for tracking stellar centroids.
Parameters: image : numpy.ndarray
FITS image read in by PyFITS
- est_x : float
Inital estimate for the x-centroid of the star
- est_y : float
Inital estimate for the y-centroid of the star
- smoothingConstant : float
Controls the degree to which the raw stellar intensity profile will be smoothed by a Gaussian filter (0 = no smoothing)
- preCropped : bool
If preCropped=False, image is assumed to be a raw image, if preCropped=True, image is assumed to be only the portion of the image near the star
- zoom : int or float
How many pixels in each direction away from the estimated centroid to consider when tracking the centroid. Be sure to choose a large enough zoom value the stellar centroid in the next exposure will fit within the zoom
- plots : bool
If plots=True, display stellar intensity profile in two axes and the centroid solution
Returns: xCenter : float
The best-fit x-centroid of the star
- yCenter : float
The best-fit y-centroid of the star
- averageRadius : float
Average radius of the SMOOTHED star in pixels
- errorFlag : bool
Boolean corresponding to whether or not any error occured when running oscaar.trackSmooth(). If an error occured, the flag is True; otherwise False.
Core developer: Brett Morris Modifications by: Luuk Visser, 2-12-2013