stella.util
Class BeamSplitterFit

java.lang.Object
  stella.util.BeamSplitterFit

All Implemented Interfaces:

Multidimensional

public class BeamSplitterFit
extends Object
implements Multidimensional

This class tries to fit data from the guider ccd to a double-peaked gaussian to resemble the STELLA-I guiding setup. The function fitted reads as

   f(x,y) = I_0·exp(-((x-x_0)²+(y-y_0)²)/2σ_0²+
        k_I I_0·exp(-((x-x_0-Δx)²+(y-y_0-Δy)²)/2σ_0²·k_s²+sky;
   

The values fitted are I_0, x_0, y_0, σ_0, k_I, k_s, and Δx, Δy, which are the peak intensity and the peak center on the CCD, the peak width, the offset of the secondary peak in Δx,y and the realative intensity k_I and relative width k_s. It is guaranteed, that Δx and Δy are constant and also k_I and k_s should not vary. So, determining these coefficients once leaves only four parameter that vary from frame to frame. The Δx Δy and k's might also be used for fitting the star plus the hole, with signs on Δ's reversed. Solving for the parameters is done with a simplex method. For each x/y coordinate pair, the function above is evaluated, the difference to the counts is calculated and squared and the squared difference is weighed with a poisson noise plus a readout noise. The sky value is estimated from the median of the outermost pixel.

Nested Class Summary

static class

BeamSplitterFit.FitsFile Reads a fits-file, extracts the counts out of it and does a beam-splitter fit.

Field Summary

private int[][]	counts The count arra, normally deduced from a fits file, x is first index.
private double	deltax On declaring hole fitting, we set the binning factor and get deltax.
static double	DELTAX After averaging some non-pinhole images, the secondary peak offset.
private double	deltay On declaring hole fitting, we set the binning factor and get deltax.
static double	DELTAY The average secondary peak offset in the mirror.
static double	FWHMMIRROR The average fwhm factor between direct and mirror in best focus.
private boolean	hole If this is true, we fit to double gauss plus pinhole.
static double	IMIRROR The average intensity factor between the direct and the mirror image.
private double	intensity On hole fitting, we set the direct intensity and get the mirror i.
static double	KI The average intensity factor of the secondary peak.
static double	KS The average fwhm relation between primary and secondary peak.
private double	sigma On hole fitting, we set the direct fwhm and get the mirror sigma.
private double	sky The sky count.
private double[][]	weight The weight of each pixel, calculateed from readout noise and Poisson.

Constructor Summary

BeamSplitterFit(int[][] ccd, double gain, double readout, boolean weigh)
Constructs a new beam splitter that can readily be used for Amoeba.

Method Summary

int	dimension() Returns 8 for normal fits, 6 for pinhole fits.
double	evaluate(VectorG fit) Evaluates the functional fit.
private double	evaluate(VectorG fit, boolean print) Evaluates the functional fit.
void	evaluateHole(int binx, int biny, double idirect, double fwhmdirect) If we want to fit the double gaussian and the pinhole as negative gaussian, we can do that here.
private static double	gauss(double i0, double x, double y, double sig) Calculates a two-dimensional gauss.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DELTAX

public static final double DELTAX

After averaging some non-pinhole images, the secondary peak offset.

See Also:

Constant Field Values

DELTAY

public static final double DELTAY

The average secondary peak offset in the mirror.

See Also:

Constant Field Values

KI

public static final double KI

The average intensity factor of the secondary peak.

See Also:

Constant Field Values

KS

public static final double KS

The average fwhm relation between primary and secondary peak.

See Also:

Constant Field Values

IMIRROR

public static final double IMIRROR

The average intensity factor between the direct and the mirror image.

See Also:

Constant Field Values

FWHMMIRROR

public static final double FWHMMIRROR

The average fwhm factor between direct and mirror in best focus.

See Also:

Constant Field Values

counts

private int[][] counts

The count arra, normally deduced from a fits file, x is first index.

weight

private double[][] weight

The weight of each pixel, calculateed from readout noise and Poisson.

sky

private double sky

The sky count.

hole

private boolean hole

If this is true, we fit to double gauss plus pinhole.

deltax

private double deltax

On declaring hole fitting, we set the binning factor and get deltax.

deltay

private double deltay

On declaring hole fitting, we set the binning factor and get deltax.

intensity

private double intensity

On hole fitting, we set the direct intensity and get the mirror i.

sigma

private double sigma

On hole fitting, we set the direct fwhm and get the mirror sigma.

Constructor Detail

BeamSplitterFit

public BeamSplitterFit(int[][] ccd,
                       double gain,
                       double readout,
                       boolean weigh)

Constructs a new beam splitter that can readily be used for Amoeba.

Method Detail

evaluateHole

public void evaluateHole(int binx,
                         int biny,
                         double idirect,
                         double fwhmdirect)

If we want to fit the double gaussian and the pinhole as negative gaussian, we can do that here. First test showed too high error if we also fit the height and with of the mirror star, but from comparison with non-pinhole affected images, we can derive the mirror intensity and the mirror fwhm from first solving on the direct image, then multiplying the intensity and fwhm of the direct image with IMIRROR and FWHMMIRROR, respectively. In this method, we have to give the intensity and the fwhm of the direct solution.

evaluate

public double evaluate(VectorG fit)

Evaluates the functional fit. The vector passed over must have a dimensionality of nine and must provide the data in the following form, ordered by index number.

• Intesity maximum of the brighter peak
• pixel-x of intensity maximum.
• pixel-y of intensity maximum.
• sigma of intensity in pixel
• relative intensity of secondary peak
• delta-x of secondary peak
• delta-y of secondary peak
• relative scaling of fwhm of secondary peak.
• level of sky background.

For each pixel pair, the deviation to the functional fix is evaluated and squared, this deviation is added together with a weighing according to Poisson noise of the data.

Specified by:

evaluate in interface Multidimensional

evaluate

private double evaluate(VectorG fit,
                        boolean print)

Evaluates the functional fit. The vector passed over must have a dimensionality of nine and must provide the data in the following form, ordered by index number.

• Intesity maximum of the brighter peak
• pixel-x of intensity maximum.
• pixel-y of intensity maximum.
• sigma of intensity in pixel
• relative intensity of secondary peak
• delta-x of secondary peak
• delta-y of secondary peak
• relative scaling of fwhm of secondary peak.
• level of sky background.

For each pixel pair, the deviation to the functional fix is evaluated and squared, this deviation is added together with a weighing according to Poisson noise of the data.

Parameters:

print - If true, we print x/y count fit count-fit

dimension

public int dimension()

Returns 8 for normal fits, 6 for pinhole fits.

Specified by:

dimension in interface Multidimensional

gauss

private static final double gauss(double i0,
                                  double x,
                                  double y,
                                  double sig)

Calculates a two-dimensional gauss.