Method and astrophotographic apparatus for acquiring images of targets in sky area

A method for acquiring an image of a target in a sky area, comprising:

• step 1, driving an image acquisition device through a controlled rotatable component to point to a position near the target in the sky area, and acquiring an image of the sky area through the image acquisition device according to a target right ascension coordinate and a target declination coordinate corresponding to a target celestial body received;
• step 2, analyzing the image of the sky area to obtain a right ascension coordinate and a declination coordinate of a center point of the image of the sky area for synchronizing the right ascension coordinate and declination coordinate to the controlled rotatable component, and determining that the image acquisition device is directed toward a position at which the right ascension coordinate and the declination coordinate are located;
• step 3, driving the image acquisition device by the controlled rotatable component to point to a target position of the target right ascension coordinate and the target declination coordinate corresponding to the target celestial body for the image acquisition device to acquire the image of the target in the sky area according to the target right ascension coordinate and the target declination coordinate corresponding to the target celestial body, as well as the right ascension coordinate and the declination coordinate currently pointed by the image acquisition device;
• and
• step 4, performing an image processing on the image of the target in the sky area to obtain a processed image of the target in the sky area;
• wherein, the controlled rotatable component is an equatorial mount, and step 1 comprises following steps:
• A, performing a polar axis alignment to the equatorial mount of an astrophotographic apparatus to enable a right ascension axis of the equatorial mount to be parallel to the axis of rotation of the Earth;
• step A comprises the following steps:
• S1, taking a first image through the image acquisition device, analyzing the first image to obtain a first coordinate file, and establishing a mapping relationship between a pixel coordinate of the first image and an equatorial coordinate through the first coordinate file;
• S2, acquiring a second image by rotating the image acquisition device to a certain angle around a polar axis, analyzing the second image to obtain a second coordinate file, and establishing a mapping relationship between a pixel coordinate of the second image and the equatorial coordinate through the second coordinate file;
• S3, calculating a pixel coordinate of an image rotation center according to the first coordinate file and the second coordinate file;
• S4, converting the pixel coordinate of the image rotation center into an equatorial coordinate of the image rotation center;
• S5, converting the equatorial coordinate of the image rotation center into a horizon coordinate of the image rotation center;
• and
• S6, calculating a difference between the horizontal coordinate of the image rotation center and a horizontal coordinate of a celestial pole, and determining whether the difference is lower than a preset first threshold;
• if the difference is lower than the preset first threshold, terminating the polar axis alignment;
• if the difference is greater than the preset first threshold, adjusting a pointing direction of the equatorial mount according to the difference, and acquiring an nth image through the image acquisition device, calculating the difference between the horizontal coordinate of the image rotation center and the horizontal coordinate of the celestial pole, and determining whether the difference is lower than the preset first threshold.