Aberration.h

Classes

Aberration -- Aberration class and calculations (full description)

class Aberration

Types

enum AberrationTypes

STANDARD

NONE

B1950

Interface

Public Members

Aberration()

Aberration(const Aberration &other)

Aberration(AberrationTypes type)

Aberration &operator=(const Aberration &other)

~Aberration()

const MVPosition &operator()(Double epoch)

const MVPosition &derivative (Double epoch)

void init()

void init(AberrationTypes type)

void refresh()

Private Members

void copy(const Aberration &other)

void fill()

void calcAber(Double t)

Description

Review Status

Reviewed By:

UNKNOWN

Date Reviewed:

before2004/08/25

Programs:

Tests:

tMeasMath

Prerequisite

Measure class, especially MEpoch
MeasData class for constants

Etymology

Aberration

Synopsis

Aberration forms the class for Aberration calculations. It is a simple container with the selected method, and the mean epoch.
The method is selected from one of the following:

Aberration::STANDARD (at 1995/09/04 the IAU1980 definition)
Aberration::NONE
Aberration::B1950

Epochs can be specified as the MJD (with defined constants MeasData::MJD2000 and MeasData::MJDB1950 or the actual MJD), leading to the following constructors:

Aberration() default; assuming JD2000, IAU1980
Aberration(method) assuming the correct default epoch of JD2000 or B1950
Aberration(method,epoch) with epoch Double(MJD).

Actual Aberration for a certain Epoch is calculated by the () operator as Aberration(epoch), with epoch Double MJD, values returned as an MVPosition.
The derivative (d^-1) can be obtained as well by derivative(epoch).
The following details can be set with the Aipsrc mechanism:

measures.aberration.d_interval: approximation interval as time (fraction of days is default unit) over which linear approximation is used
measures.aberration.b_usejpl: use the JPL database values for IAU1980. Else analytical expression, relative error about 10^-9 Note that the JPL database to be used can be set with measures.jpl.ephemeris (at the moment of writing DE200 (default), or DE405). If using the JPL database, the d_interval (and the output of derivative()) are irrelevant.

Example

Motivation

To calculate the Aberration angles. An alternate route could have been a global function, but having a simple container allows caching of some calculations for speed.
Using MJD (JD-2400000.5) rather than JD is for precision reasons.