Ruwe From Fit Normalization
Derive RUWE from chi-square, fit degrees of freedom, and caller-supplied magnitude/color normalization; no catalog calibration table is embedded.
Description
RUWE divides a fit's unit-weight error by a supplied magnitude/color normalization.
RUWE divides a fit's unit-weight error by a supplied magnitude/color normalization. The normalization is source-dependent and is separate from the fit's chi-square and degrees of freedom.1
Derive RUWE from chi-square, fit degrees of freedom, and caller-supplied magnitude/color normalization; no catalog calibration table is embedded.
When to use Ruwe From Fit Normalization
Use this tool to derive RUWE from chi-square, fit degrees of freedom, and caller-supplied magnitude/color normalization; no catalog calibration table is embedded.
Prepare the source, detector or coordinate measurements. Confirm frame, epoch, angular units, axis directions and the stated RA proper-motion convention before entering values.
How to use Ruwe From Fit Normalization and understand its results
- Prepare the source, detector or coordinate measurements. Confirm frame, epoch, angular units, axis directions and the stated RA proper-motion convention before entering values.
- Enter chiSquare, goodObservations, fittedParameters, normalizationU0, maximumRuwe using the field table and calculation rules, then run the tool.
- Read unitWeightError, ruweValue, passesSuppliedCriterion. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| chiSquare | Chi square | number | Required |
| goodObservations | Good observations | integer | Required |
| fittedParameters | Fitted parameters | integer | Required |
| normalizationU0 | Normalization u 0 | number | Required |
| maximumRuwe | Maximum ruwe | number | Required |
Enter nonnegative chi-square, positive integer observation count, nonnegative integer parameter count, positive u0 and positive RUWE threshold. Degrees of freedom must be positive. Return UWE, RUWE and an inclusive passesSuppliedCriterion flag. Zero chi-square gives zero errors.
UWE=sqrt(chiSquare/(goodObservations−parameters)); RUWE=UWE/u0 Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| unitWeightError | Unit weight error | number |
| ruweValue | Ruwe value | number |
| passesSuppliedCriterion | Passes supplied criterion | boolean |
{
"input": {
"chiSquare": 20,
"goodObservations": 10,
"fittedParameters": 5,
"normalizationU0": 2,
"maximumRuwe": 1.4
},
"output": {
"unitWeightError": 2,
"ruweValue": 1,
"passesSuppliedCriterion": true
}
}Limitations and assumptions
No catalog normalization table or universal quality cutoff is embedded. A passing result does not prove a single-star model or reliable astrometry, and correlated/error-model defects are not diagnosed.
Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors. A successfully returned false flag is an evaluated outcome; its meaning is explained above.
Alternative or Complementary methods
Use Astrometric Reduced Chi Square: Evaluate weighted astrometric residual chi-square and a supplied reduced-chi-square criterion; independent correctly estimated errors are assumed. For a complementary task, use Five Parameter Design Rank: Audit rank of a position/proper-motion/parallax design from supplied epoch offsets and RA*/Dec parallax factors; conditioning and measurement weights are not assessed.
References
-
Ruwe From Fit Normalization — tool.io
Similar or alternative tools
- Astrometric Reduced Chi Square
Evaluate weighted astrometric residual chi-square and a supplied reduced-chi-square criterion; independent correctly estimated errors are assumed.
- Five Parameter Design Rank
Audit rank of a position/proper-motion/parallax design from supplied epoch offsets and RA*/Dec parallax factors; conditioning and measurement weights are not assessed.