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A sequential number for the measurement

Image

The name of the image that was measured

Obj

The source number. If sources touch and are merged during the detection process, one of the numbers is discarded, making the Obj values generally not a continuous sequence.

<X>

The mean X position, measured in world coordinates. If Precision Centroid or Precision FWHM is checked on the Post-process page, this is measured in the same way as an interactively marked centroid using the settings on the Centroid page.

<Y>

The mean Y position, measured in world coordinates. If Precision Centroid or Precision FWHM is checked on the Post-process page, this is measured in the same way as an interactively marked centroid using the settings on the Centroid page.

Col

The mean Column position, measured in pixel coordinates. If Precision Centroid or Precision FWHM is checked on the Post-process page, this is measured in the same way as an interactively marked centroid using the settings on the Centroid page.

Row

The mean Row position, measured in pixel coordinates. If Precision Centroid or Precision FWHM is checked on the Post-process page, this is measured in the same way as an interactively marked centroid using the settings on the Centroid page.

Total Lum

The total luminosity (intensity) of the source relative to zero. This value disregards the background setting but, as with all properties, includes only those pixels that satisfy the threshold condition on the Detect page.

Net Lum

The net luminosity (intensity) of the source above the background. If you think of pixel value as defining a 3 dimensional surface, the Lum value is the volume of the surface above the background as configured on the Background page. However, pixels are only included in this volume if their value satisfies the threshold condition on the Detect page.

Mean Lum

The net luminosity (Net Lum value) divided by the area.

Std Dev

The standard deviation of the net luminosity (Net Lum value).

Ellip

The ellipticity, measured as 1 – (minor axis / major axis).

Angle

The angle of the major axis relative to the positive X axis (0 degrees), increasing through the positive Y axis (90 degrees). The angle is adjusted to fall in the range -90 to +90 degrees.

Area

The area, in pixels, of the source above the threshold. This is threshold dependent.

Maximum

The maximum intensity. This is the pixel value of the highest pixel inside the source.

Minimum

The minimum intensity. This is the pixel value for the threshold value above the background.

FWHM

(Precision FWHM)

The Full Width at Half maximum brightness. This measures the point spread function of the source profile. This is reported only of the Precision FWHM option is checked on the Post-process page.

CI

Concentration Index. This is the ratio of the Effective Diameter divided by 2 times the radius of gyration. The Effective diameter is the diameter of a circle having the same area. The radius of gyration is the radius for the second moment of the intensity distribution (analogous to the moment of inertia of a rotating mass distribution). This is threshold dependent.

Major Axis

The major axis length in units of pixels. This is threshold dependent.

Minor Axis

The minor axis length in units of pixels. This is threshold dependent.

Kurtosis

The source profile kurtosis. This measures the "flatness" of the intensity distribution.

X Skew

The source profile skewness in the X direction. This measures the asymmetry of the intensity distribution.

Y Skew

The source profile skewness in the Y direction. This measures the asymmetry of the intensity distribution.

Background

The background value evaluated at the average position of the source (at <X> and <Y>).

Mag

(Aperture Photometry)

The magnitude of the source above its local background. It is integrated within an elliptical aperture surrounding the object. The Zero point value specified in the Aperture Photometry Setup dialog is also applied. This value and its related measurements are reported only if the Aperture Photometry option is checked on the Post-process page.

Error

(Aperture Photometry)

The uncertainty in the magnitude (Mag). This is computed using the signal and an error estimate based on variation in the pixel values inside the background annulus surrounding the source.

Error(T)

(Aperture Photometry)

The theoretical estimate of the uncertainty in the magnitude (Mag). This is computed using signal at each point along with the gain, readout noise, and exposure time for the image.

Net Count

(Aperture Photometry)

The total signal of the source above its local background. This is also known as "count volume". It is integrated within an elliptical aperture surrounding the object, and is used to compute the magnitude.

S/N

(Aperture Photometry)

The Signal To Noise ratio for the detected signal inside the aperture that measures the magnitude and net count.

Bg Local

(Aperture Photometry)

The precision background measured from pixels inside the annulus between the inner and outer background apertures. This is more accurate for a precision intensity measurement than is obtained using the Background surface value at the position of the source. This value is effective at the center position of the object.

FWHM Peak

(Precision FWHM)

The Peak value (above background) from the FWHM calculation. This is measured only if FWHM is selected in the post-processing options. This is not threshold dependent. This is reported only of the Precision FWHM option is checked on the Post-process page.

FWHM Bg

(Precision FWHM)

The background value from the FWHM calculation. This is measured only if FWHM is selected in the post-processing options. This is not threshold dependent. Compare its value with the computed background value based on the Background strategy. This is reported only of the Precision FWHM option is checked on the Post-process page.

Min X

The minimum Column position of the source.

Max X

The maximum Column position of the source.

Min Y

The minimum Row position of the source.

Max Y

The maximum Row position of the source.

X at Min Y

The Column position at the minimum Row position of the source.

X at Max Y

The Column position at the maximum Row position of the source.

Y at Min X

The Row position at the minimum Column position of the source.

Y at Max X

The Row position at the maximum Column position of the source.

X at Min Lum

The Column position at the minimum Intensity of the source.

X at Max Lum

The Column position at the minimum Intensity of the source.

Y at Min Lum

The Row position at the minimum Intensity of the source.

Y at Max Lum

The Row position at the minimum Intensity of the source.