Method for adjusting an equatorial or altazimuth mount
The present invention relates to a method for readjusting a parallactic or azimuthal mounting, comprising a device which is intended for positioning and moving a telescope with a camera and can be aligned and readjusted by means of at least one image sensor and an electromotorized controller, characterized in that the image sensor acts as a main recording sensor of the camera and at the same time as an alignment sensor and readjustment control sensor, wherein before and after a main image is taken at least one control image is taken with a shorter exposure time and these control images are compared with one another, or at least a main image itself acts as a control image and is compared with at least one previous main image, or a short-exposed control image is compared with the main image itself and the correction values for the readjustment of the mounting are determined by the image offset and the time difference of the images taken. The method is the prerequisite for easy, error-free operation of an astronomical mounting for the purpose of long-exposure astronomical photography.
1. A method for adjusting an equatorial or altazimuth mount with electric motors based on data received from an image sensor, the mount carrying a telescope with a camera,
wherein the image sensor serves a main recording sensor of the camera and also as an alignment sensor and adjustment control sensor,
and wherein before and after a main image is taken two control images with a shorter exposure time than the main image are taken and these control images are compared to one another,
or at least one main image serves as a control image and is compared to at least one previous main image,
or a short exposure control image is compared to a main image,
and wherein correction values for the adjustment of the mount are determined by an image offset and a time difference (dt) of the images taken,
wherein a correction value for a movement of axes of the mount is determined and an error in the adjustment is regularly measured comprising:
a) taking a control image (K(n));
b) taking a main image (H(n));
c) taking a further control image (K(n+1));
d) determining a time difference (dt) between the control image (K(n)) and the further control image (K(n+1))
e) determining a subpixel accurate image offset in image x-coordinates (BVx) and in image v-coordinates (BVy) between the control image K(n) and the further control image K(n+1);
f) determining an offset in celestial right ascension coordinates (HVRa) and celestial declination coordinates (HVDek) based on the image offset in image x-coordinates (BVx) and the image offset in image y-coordinates (BVy) and a position of the image in celestial coordinates right ascension (HRa) and declination (HDek);
g) calculating an angular position of a right ascension axis (Ra(t)) and an angular position of a declination axis (Dek(t)) over time (t), based on a sidereal angular velocity (Vsidereal) as
Ra(t)=Vsidereal*t,
Dek(t)=0;
h) determining a corrected right ascension angular velocity (VRaKorr) and a corrected declination angular velocity (VDekKorr) on the basis of the time difference (dt), the sidereal angular velocity (Vsidereal), the offset in celestial right ascension coordinates (HVRa) and the celestial declination coordinates (HVDek) as
VRaKorr=(HVRa−deltaRaRefrakt)/dt+Vsidereal,
VDekKorr=(HVDek−deltaDecRefrakt)/dt;
i) moving the right ascension axis (Ra(t)) and the declination axis (Dek(t)) over time (t) based on
Ra(t)=VRaKorr*t,
Dek(t)=VDekKorr*t;
j) determining a new corrected right ascension angular velocity (VRaKorr′) and a new corrected declination angular velocity (VDekKorr′) on the basis of the time difference (dt), the offset in celestial right ascension coordinates (HVRa), the celestial declination coordinates (HVDek), and the previously determined corrected right ascension angular velocity (VRaKorr) and the previously determined corrected declination angular velocity (VDekKorr) as
VRaKorr′=HVRa/dt+VRaKorr,
VDekKorr′=HVDek/dt+VDekKorr; and
k) repeating steps i)-k).
2. A method for adjusting an equatorial or altazimuth mount with electric motors based on data received from an image sensor, the mount carrying a telescope with a camera,
wherein the image sensor serves a main recording sensor of the camera and also as an alignment sensor and adjustment control sensor,
and wherein before and after a main image is taken two control images with a shorter exposure time than the main image are taken and these control images are compared to one another,
or at least one main image serves as a control image and is compared to at least one previous main image,
or a short exposure control image is compared to a main image,
and wherein correction values for the adjustment of the mount are determined by an image offset and a time difference (dt) of the images taken,
wherein a correction value for a movement of axes of the mount is determined and an error in the adjustment is regularly measured, comprising:
a) taking a control image (K(n));
b) taking a main image (H(n));
c) taking a further control image (K(n+1));
d) determining a time difference (dt) between the control image (K(n)) and the further control image (K(n+1))
e) determining a subpixel accurate image offset in image x-coordinates (BVx) and in image y-coordinates (BVy) between the control image K(n) and the further control image K(n+1);
f) determining an offset in celestial right ascension coordinates (HVRa) and celestial declination coordinates (HVDek) based on the image offset in image x-coordinates (BVx) and the image offset in image y-coordinates (BVy) and a position of the image in celestial coordinates right ascension (HRa) and declination (HDek);
g) calculating an angular position of a right ascension axis (Ra(t)) and an angular position of a declination axis (Dek(t)) over time (t), based on a sidereal angular velocity (Vsidereal) as
Ra(t)=Vsidereal*t,
Dek(t)=0
h) determining a corrected right ascension angular velocity (VRaKorr) and a corrected declination angular velocity (VDekKorr) on the basis of the time difference (dt), the sidereal angular velocity (Vsidereal), the offset in celestial right ascension coordinates (HVRa) and celestial declination coordinates (HVDek), and a differential right ascension refraction (deltaRaRefrakt) and differential declination refraction (deltaDecRefrakt) as
VRaKorr=(HVRa−deltaRaRefrakt)/dt+Vsidereal,
VDekKorr=(HVDek−deltaDecRefrakt)/dt;
i) moving the right ascension axis (Ra(t)) and the declination axis (Dek(t)) over time (t) based on
Ra(t)=VRaKorr*t,
Dek(t)=VDekKorr*t;
j) determining a new corrected right ascension angular velocity (VRaKorr′) and a new corrected declination angular velocity (VDekKorr′) on the basis of the time difference (dt), the offset in celestial right ascension coordinates (HVRa), the celestial declination coordinates (HVDek), the previously determined corrected right ascension angular velocity (VRaKorr) and the previously determined corrected declination angular velocity (VDekKorr), and the differential right ascension refraction (deltaRaRefrakt) and the differential declination refraction (deltaDecRefrakt) as
VRaKorr′=(HVRa−deltaRaRefrakt)/dt+VRaKorr,
VDekKorr′=(HVDek−deltaDecRefrakt)/dt+VdekKorr; and
k) repeating steps i)-k).