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## Class Position

The basic class in the coords library. The Position class is designed to permit users to define a position and then access many representations of it.
Method Summary
Position ```__init__(self, input, equinox, system, units)```
string `__repr__(self)`
`angsep.AngSep` ```angsep(self, other)```
Computes the angular separation (great circle distance) between two Positions.
(float,float) ```b1950(self, timetag)```
Return the position in Mean FK4 B1950 coordinates
(float,float) `dd(self)`
Return position in decimal degrees
string `details(self)`
Return system & equinox
(float,float) ```ecliptic(self, timetag)```
Return the position in IAU 1980 Ecliptic coordinates
(float,float) ```galactic(self, timetag)```
Return the position in IAU 1958 Galactic coordinates.
string `hmsdms(self)`
Return position in hms dms
(float, float) ```j2000(self, timetag)```
Return the position in Mean FK5 J2000 coordinates
(float,float) `rad(self)`
(float,float) ```tpmstate(self, endstate, epoch, equinox, timetag)```
This method allows the expert user to call the blackbox routine of the TPM library directly, for access to more state transitions than are supported in this interface.
Boolean ```within(self, other, epsilon, units)```
returns true if "other" is within "epsilon" of "self"
None `_parsecoords(self)`
Convert from input string into internal representation (decimal degrees) by invoking the appropriate type of Coord.
`_set_tpmstate(self)`
Define the state for TPM based on equinox and system

Instance Variable Summary
`Coord` `coord`: a "smart" representation of the position
`equinox`: at which the coordinates were specified
`input`: the input used to create the Position
string `system`: celestial, galactic, ecliptic
string `units`: in which the coords were specified (degrees, radians)
(float,float) `_internal`: the internal representation of the position (decimal degrees)
integer `_tpmstate`: the TPM state of the position

Method Details

### __init__(self, input, equinox='J2000', system='celestial', units='degrees')(Constructor)

Parameters:
`input` - coordinates of the position
(type=string (hh:mm:ss.ss +dd:mm:ss.sss) or tuple of numbers (dd.ddd, dd.ddd))
`equinox` - in which the coords are specified
(type=string)
`system` - celestial, galactic, ecliptic, etc
(type=string)
`units` - degrees or radians
(type=string)
Returns:
Position

Returns:
string

### angsep(self, other)

Computes the angular separation (great circle distance) between two Positions.
Parameters:
`other` - another `Position`
Returns:
angular separation
(type=`angsep.AngSep`)

### b1950(self, timetag=None)

Return the position in Mean FK4 B1950 coordinates
Parameters:
`timetag` - Timetag of returned coordinate
(type=`astrodate.AstroDate`)
Returns:
(ra, dec) tuple in decimal degrees
(type=(float,float))

### dd(self)

Returns:
Position in decimal degrees
(type=(float,float))

### details(self)

Returns:
system & equinox
(type=string)

### ecliptic(self, timetag=None)

Return the position in IAU 1980 Ecliptic coordinates
Parameters:
`timetag` - Timetag of returned coordinate
(type=`astrodate.AstroDate`)
Returns:
(le,be) tuple in decimal degrees
(type=(float,float))

### galactic(self, timetag=None)

Return the position in IAU 1958 Galactic coordinates.
Parameters:
`timetag` - Timetag of returned coordinate
(type=`astrodate.AstroDate`)
Returns:
(l,b) tuple in decimal degrees
(type=(float,float))

### hmsdms(self)

Returns:
Position in hms dms
(type=string)

### j2000(self, timetag=None)

Return the position in Mean FK5 J2000 coordinates
Parameters:
`timetag` - Timetag of returned coordinate
(type=`astrodate.AstroDate`)
Returns:
(ra, dec) tuple in decimal degrees
(type=(float, float))

Returns:
(type=(float,float))

### tpmstate(self, endstate, epoch=None, equinox=None, timetag=None)

This method allows the expert user to call the blackbox routine of the TPM library directly, for access to more state transitions than are supported in this interface. Little documentation is provided here because it is assumed you know what you are doing if you need this routine.
Parameters:
`endstate` - as defined by the TPM state machine
(type=integer)
`epoch` - in Julian date; default J2000
(type=float)
`equinox` - in Julian date; default self._tpmequinox
(type=float)
`timetag` - Timetag of returned coordinate
(type=`astrodate.AstroDate`)
Returns:
transformed coordinates in decimal degrees
(type=(float,float))

### within(self, other, epsilon, units='arcsec')

returns true if "other" is within "epsilon" of "self"
Parameters:
`other` - Another position
(type=`Position`)
`epsilon` - angular separation
(type=`angsep.AngSep` or number)
`units` - of the angular separation, if it's specified as a number
(type=string ('arcsec','degrees'))
Returns:
Boolean

### _parsecoords(self)

Convert from input string into internal representation (decimal degrees) by invoking the appropriate type of Coord. Default float values will be interpreted as decimal degrees; radians will have to be specified as such.

Legitimate units: hmsdms, decimal degrees, radians
• hmsdms = "hh:mm:ss.ss -dd:mm:ss.ss"
• decimal degrees = (ddd.dd, -ddd.dd)
Returns:
None

To Do: add support for 3vectors ("xx.xxx yy.yyy zz.zzz")

### _set_tpmstate(self)

Define the state for TPM based on equinox and system

Instance Variable Details

### coord

a "smart" representation of the position
Type:
`Coord`

### equinox

at which the coordinates were specified

### input

the input used to create the Position

### system

celestial, galactic, ecliptic
Type:
string

### units

in which the coords were specified (degrees, radians)
Type:
string

### _internal

the internal representation of the position (decimal degrees)
Type:
(float,float)

### _tpmstate

the TPM state of the position
Type:
integer

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