Method of A. A. Rambaut

The methods of A.A. Rambaut is based on the measurement of one star and and the reduction of the movement in both directions, the declination and th rightascension.

Where in the sky

The declination and the local hour angle can be chosen at will with the exception of the celestial equator and the neighboring region. On the celestial equator the method fails completely.

Is the star trail in one of the directions small then choose a star which has a hour angle which differs about 90^o.

Alignment of the measurement filed and orientation of the axes

The alignment of the measurement field is equatorial.

The positive x-axis points in the direction of the positive rightascension, that means toward East. The positive y-axis points in the direction of the negative declination, that means towards the South.

Duration of the measurement

The duration varies between 10 and 120 minutes.

Zero point

The zero point is the true celestial pole. After the alignment the hour axis has to be lifted by the value Rb towards the zenith.

Procedure

After the star has been centered it is time to track the star without any intervention. Read the position after about 30 minutes on the measurement field. Enter both values X and Y in the fields X direction and Y direction in units of the grid. Enter the measurement duration in seconds into the field Observing period. Enter into the field Resolution per unit the grid unit in arc seconds and hit submit.

Example

With the following parameters

Latitude: +47
Longitude: -7.601
Height: 550
Temperature: 10
Date: 2001:09:30
Time: 22:04:21
Time zone: cest
Observing period: 1371
Rightascension: 279.23458
Declination: 38.783
Correction star Declination: -20
X direction: +0.36
Y direction: +2.32
Resolution per unit: 5

you obtain the following results

Rambaut A : -114.07 arcsec
Rambaut k : 125.14 arcsec
Rambaut h : 328.37 degree
Rambaut lambda : 146.96 arcsec
Move the north end of the hour axis 22.81 units to the WEST
with star at declination -20.00 degree 21.08 units to the WEST
Lower elevation of the hour axis 25.03 units

Comments, questions, corrections? markus.wildi@one-arcsec.org