Setting

Default

Description

Maximum magnitude difference

1

Establishes the maximum magnitude difference from image to image, where the object is still seen as the same object. (Applies to moving objects only.)

Maximum rate

150

Establishes the maximum movement rate in pixels per hour from image to image, where the object is still seen as the same object. Use larger values for near Earth objects; use smaller values to avoid spurious detections. (Applies to moving objects only.)

Maximum linear pixel variation

1.5

Establishes how far out of line an objects can be and still be considered one object across multiple images. CCDSoft predicts where the object should be on the third and subsequent images, and then looks within a radius equal to this pixel variation to see if it can find an object. If you increase this too far, CCDSoft will find object that aren’t in a line, resulting in spurious detections. (Applies to moving objects only.)

Minimum movement

3

Establishes the minimum movement from image to image for an object to be considered a candidate minor planet. If this is set to too small of a value, you will find too many spurious candidates. (Applies to moving objects only.)

Computed vs. measured maximum

3

CCDSoft computes the next position of the minor planet based on the time of each exposure. If your orbital elements are inaccurate, you might need a higher value for this parameter so that CCDSoft can find the minor planet candidate. (Applies to moving objects only.)

Deblending sub-thresholds

32

An integer value. Deblending is the separation of overlapping objects. 32 is the maximum useful number of thresholds. Smaller numbers can be used to reduce the amount of memory used for deblending, but deblending performance may suffer as a result.

Pixels above threshold

5

An integer value. Specifies an area in pixels that defines the smallest possible object found.

Detection threshold

1.25

Larger numbers mean fewer objects will be detected.

The Source Extraction manual states that this parameter should be less than or equal to 2. However, Software Bisque has found that setting this value to 10 or higher can give good results for star detection in galaxies and nebulas.

Use the Show Inventory command to compare the number of objects that are detected in a given image using different values for the Detection Threshold.

Analysis threshold

1.5

Threshold in brightness (relative to background) at which star-related parameters operate.

Minimum contrast

0.005

The useful range of values is between 0.001 and 0.1. Smaller numbers lead to more aggressive deblending, and thus more objects being found. A value of 1 effectively turns off deblending.

Mask type

None

The available mask types are none, blank, and correct. Masking is applied to neighbors for photometry. None turns off masking; blank puts pixels belonging to neighbors to zero; correct replaces values with pixels at an equal distance on the other side of the object centroid.

Aperture diameter

5

The aperture, in pixels, used for scanning the image.

kron factor

2.5

A scaling parameter related to the first-order moment.

Minimum radius

3.5

Minimum radius is based on the units of A_IMAGE and B_IMAGE

Saturation level

65000

Saturation level for your CCD camera. Defined as the full-well capacity divided by the gain.

Magnitude zero point

10

Zero point offset applied to all magnitudes.

Mesh size

32

Defines how finely or coarsely the background filtering mask is divided in order to search for objects. If the mesh is too fine, the mesh boundaries can fall on objects too often and lead to locally inaccurate results. The mesh size is the size of the cell in the mesh, in pixels.

Filter size

Size of a median filter applied to the background. 1 means no filtering. Use a filter (e.g., 2x2 or 3x3) to compensate for small mesh sizes or in the case of large artifacts in the image.

Detector gain

0

The gain of the CCD detector.

Size of pixel

1.4

Pixel scale in arcseconds.

Seeing

1.2

The FWHM (full width at half maximum) of the stars in the image.

Clean

unchecked

When checked, faint (spurious) detections are removed from the object catalog before writing to disk.

Cleaning efficiency

1

Determines the aggressiveness of the cleaning.