Astropy: initializing a custom coordinate frame

Question

I am developing a raspberry Pi application for controlling an amateur telescope on an AltAzimutal mount.

The azimuthal axis is not perfectly aligned with the zenith. In this case, you can point to 2 or 3 stars and find the transformation matrix between the apparent telescope and the equatorial coordinates. This method can be seen here . I want to implement this method with astropy, but I don’t understand how I can determine the reference frame of an inclined telescope.

I compute the transformation matrix and give it as an argument for the new frame. But I get an error message.

Here is the code:

 # coding: utf-8

 """ Astropy coordinate class for the tilted telescope coordinate system """

from __future__ import division, print_function

# Third-party
import numpy as np
from numpy import cos, sin

from astropy.coordinates import frame_transform_graph
from astropy.coordinates.angles import rotation_matrix

import astropy.coordinates as coord
import astropy.units as u


__all__ = ["MyFrame"]


import astropy.coordinates as coord


class MyFrame(coord.BaseCoordinateFrame):
    """
    A topocentric spherical coordinate system defined by the telescope on tilted Altzimutal mount
     http://www.geocities.jp/toshimi_taki/aim/aim.htm    

    Parameters
    ----------
    matrix: the transformation matrix obtained by 2 stars method ( http://www.geocities.jp/toshimi_taki/aim/aim.htm)  
    representation : `BaseRepresentation` or None
        A representation object or None to have no data (or use the other keywords)
    Lambda : `Angle`, optional, must be keyword
        The longitude-like angle corresponding to Sagittarius' orbit.
    Beta : `Angle`, optional, must be keyword
        The latitude-like angle corresponding to Sagittarius' orbit.

    """
    default_representation = coord.UnitSphericalRepresentation

    frame_specific_representation_info = {
        'spherical': [coord.RepresentationMapping('lon', 'az'),
                      coord.RepresentationMapping('lat', 'alt'),
                      coord.RepresentationMapping('distance', 'distance')],
        'unitspherical': [coord.RepresentationMapping('lon', 'az'),
                          coord.RepresentationMapping('lat', 'alt')]
    }


    def __init__(self,matrix,*args, **kwargs):
        super(MyFrame, self).__init__(*args, **kwargs)
        self.matrix=matrix


# equatorial (ICRS )  to tilted telescope AltAz coordinates
@frame_transform_graph.transform(coord.FunctionTransform, coord.ICRS, MyFrame)
def equatorial_to_telescope(icrs_frame, telescope_frame):
    """ Compute the transformation from icrs spherical to
        topocentric telescope coordinates.
    """
    matrix=np.matrix(([1,0,0],[0,1,0],[0,0,1]))
    C0=icrs_frame.represent_as(coord.CartesianRepresentation).xyz.value

    l0=matrix.dot(C0)

    altAZ=coord.SkyCoord(x=l0[0,0],y=l0[0,1],z=l0[0,2],frame='altaz',representation='cartesian').represent_as(coord.UnitSphericalRepresentation)

    return MyFrame(az=altAZ.lon.to(u.deg),  alt=altAZ.lat.to(*u.deg))

Here is the call to this class:

import myFrame as fr
import astropy.coordinates as coord
import astropy.units as u
import numpy as np

matrix=np.matrix(([1,0,0],[0,1,0],[0,0,1]))

m=fr.MyFrame()
icrs = coord.ICRS(152.88572*u.degree, 11.57281*u.degree)
mfr=icrs.transform_to(m)

Here is the error code:

TypeError                                 Traceback (most recent call last)
<ipython-input-14-33f2cd1fa087> in <module>()
----> 1 mfr=icrs.transform_to(m)

/home/maksim/MyPython/astropy/coordinates/baseframe.pyc in transform_to(self, new_frame)
    839             msg = 'Cannot transform from {0} to {1}'
    840             raise ConvertError(msg.format(self.__class__, new_frame.__class__))
--> 841         return trans(self, new_frame)
    842 
    843     def is_transformable_to(self, new_frame):

/home/maksim/MyPython/astropy/coordinates/transformations.pyc in __call__(self, fromcoord, toframe)
    915                     frattrs[inter_frame_attr_nm] = attr
    916 
--> 917             curr_toframe = t.tosys(**frattrs)
    918             curr_coord = t(curr_coord, curr_toframe)
    919 

TypeError: __init__() takes at least 2 arguments (1 given)

: astropy BaseFrame.

BaseCoordinateFrame ?

Answer 1

__init__ , . , , , , FrameAttribute, : http://docs.astropy.org/en/stable/coordinates/frames.html#defining-a-new-frame

, , , . , , __init__ / - , . , .

matrix , (.. self.matrix) .

, , , - FrameAttribute, ( ). __init__, .