Class AngSep
The AngSep class lets the user compare the angular separation between
different position.Positions without having to think
too much about units.
Each AngSep object is created with a particular length in a particular
set of units. These are then converted into an internal representation
which is used for all math and comparisons.
All unit checks are performed by checking the first few letters of the
unit string, to provide more flexibility for the user. (eg,
"arc" "arcs" "arcsec"
"arcseconds" will all evaluate to arcseconds.)
All math and comparisons can be done either between two AngSep
objects, or between an AngSep object and a number. In the latter case,
the number is assumed to have the same units as the AngSep object.
Example:
>>>
>>> a=angsep.AngSep(5)
>>> a
5.000000 arcsec
>>>
>>> b=angsep.AngSep(3)
>>> a+b
8.000000 arcsec
>>> a*3
15.000000 arcsec
>>>
>>> p1=P.Position('12:34:45.23 45:43:21.12')
>>> p2=P.Position('12:34:47.34 45:43:23.0')
>>> sep=p1.angsep(p2)
>>> eps=angsep.AngSep(30,units='arcsec')
>>> p1.within(p2,eps)
True
>>> p2.within(p1,20)
False
Note: Angular Separations are inherently positive: negative separations have
no physical meaning, and are forbidden.
| Method Summary |
| AngSep
|
__init__(self,
value,
units) |
| |
__add__(self,
other)
|
| |
__eq__(self,
other)
|
| |
__ge__(self,
other)
|
| |
__gt__(self,
other)
|
| |
__le__(self,
other)
|
| |
__lt__(self,
other)
|
| |
__mul__(self,
other)
|
| |
__ne__(self,
other)
|
| |
__radd__(self,
other)
|
| string
|
__repr__(self) |
| |
__rmul__(self,
other)
|
| |
__rsub__(self,
other)
|
| |
__sub__(self,
other)
|
| Boolean
|
approx(self,
other,
epsilon)
True if "self" and "other" are equal to within
"epsilon". |
| float
|
arcsec(self)
Return separation in arcsec |
| float
|
degrees(self)
Return separation in degrees |
| float
|
radians(self)
Return separation in radians |
| None
|
setunits(self,
units)
Sets the units of the public representation, and converts the
publically visible value to those units |
| Instance Variable Summary |
| string |
units: units in which the magnitude is expressed (arcsec, degrees, or
radians) |
| number |
value: magnitude of the angular separation |
__init__(self,
value,
units='arcsec')
(Constructor)
-
- Parameters:
value -
magnitude of the angular separation
(type=number)
units -
arcsec or degrees
(type=string)
- Returns:
-
AngSep
- Raises:
ValueError -
if value < 0. Negative separations are physically
meaningless and thus forbidden.
|
__repr__(self)
(Representation operator)
-
- Returns:
-
string
|
approx(self,
other,
epsilon)
True if "self" and "other" are equal to within
"epsilon". "epsilon" is considered to have the same
units as self.
-
- Parameters:
other
(type=AngSep or number (units of self))
epsilon
(type=AngSep or number (units of self))
- Returns:
-
Boolean
Note: This is not implemented as 'abs(self-other)<epsilon' because of the
prohibition on negative separations.
|
arcsec(self)
-
- Returns:
-
separation in arcsec
(type=float)
|
degrees(self)
-
- Returns:
-
separation in degrees
(type=float)
|
radians(self)
-
- Returns:
-
separation in radians
(type=float)
|
setunits(self,
units)
Sets the units of the public representation, and converts the
publically visible value to those units
-
- Parameters:
units -
radians, arcsec, or degrees
(type=string)
- Returns:
-
None
|
| Instance Variable Details |
units
units in which the magnitude is expressed (arcsec, degrees, or
radians)
-
- Type:
-
string
|
value
magnitude of the angular separation
-
- Type:
-
number
|