B1950 to J2000 Modern Reconverter
Static approximate B1950-to-J2000 orientation-only rotation using conventional matrix; E-terms, proper motion, epoch propagation and FK4/FK5 catalog conversion omitted explicitly.
Description
B1950 to J2000 Modern Reconverter: return approximate right ascension degrees, approximate declination degrees, full fk4 fk5 conversion applied.
B1950 and J2000 identify different historical astrometric reference conventions. A simple orientation matrix is only part of a full FK4/FK5 conversion.
This tool returns approximate right ascension degrees, approximate declination degrees, full fk4 fk5 conversion applied. Use the stated units and model convention when interpreting these fields.
When to use this tool
Use this tool when the supplied inputs match the specific operation described above and you need a repeatable result under its stated convention.
- Check the supported input and output contract against an existing calculation or observation.
- Use the complete example to confirm units, selector spelling and result interpretation.
How to use the tool and how it works
- Enter every field in the input table using the stated units and the exact supported selector spelling where applicable.
- Run the tool. Correct input errors before interpreting an output.
- Read the result fields below; use accompanying flags and the stated sign, boundary or model convention when interpreting a number.
Convert right ascension and declination to a unit vector, multiply by the fixed stored matrix, then recover angles with atan2. Normalize right ascension into [0,360).1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| rightAscensionDegrees | Right ascension degrees. Degrees. | Finite number; from 0 to 360 inclusive |
| declinationDegrees | Declination degrees. Degrees. | Finite number; from -90 to 90 inclusive |
| Output field | Interpretation |
|---|---|
| result | Object containing the following named result fields. |
| result.approximateRightAscensionDegrees | Approximate right ascension degrees; use the stated units and sign convention. |
| result.approximateDeclinationDegrees | Approximate declination degrees; use the stated units and sign convention. |
| result.fullFk4Fk5ConversionApplied | Always false: the fixed-matrix result is only an approximate rotation. |
{
"input": {
"rightAscensionDegrees": 0,
"declinationDegrees": 0
},
"output": {
"result": {
"approximateRightAscensionDegrees": 0.6407058145774651,
"approximateDeclinationDegrees": 0.27834100655414085,
"fullFk4Fk5ConversionApplied": false
}
}
}Limitations and assumptions
- The approximation omits proper motion, E-terms and a full catalog-system transformation. fullFk4Fk5ConversionApplied is false.
- Every declared field is required and unexpected fields are rejected. Numeric inputs must be finite; input errors are distinct from a valid false result or an explicitly qualified output.
- Extremely large inputs and nonfinite or excessively large outputs are rejected. List positions reported by the tool use zero-based indices unless stated otherwise.
Alternative or Complementary methods
Check the underlying observations, units and conventions independently before using the result in a larger workflow. The tools listed below address nearby tasks; compare their inputs and scope before substituting one for this operation.
References
Similar or alternative tools
- J2000 to B1950 Besselian Coordinate Legacy Converter
Static approximate J2000-to-B1950 orientation-only rotation using conventional matrix; E-terms, proper motion, epoch propagation and FK4/FK5 catalog conversion omitted explicitly.
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Annual aberration traces an ideal ellipse whose shape depends on ecliptic latitude.