During astronomical observations, amateur astronomers usually use one of such processes: (1) Determining the position of celestial bodies by consulting astronomical almanac, star maps, etc.; adjusting the telescope, looking for the celestial body for observing, after locating the celestial body, setting the photographic equipment to take photos. During the whole observation process, there are a lot of inconvenience, such as, one must consult the relevant information to determine the positions of celestial bodies before each observation as the celestial bodies are constantly moving in the sky, but the ephemeris is heavy and non-intuitive, the simple star chart can only used to observe at specified times due to the moving of the celestial bodies; to adjust the telescope manually is very complicated; and it's not convenient to take photos through the telescope. (2) Using a guiding software and an electric equatorial to achieve automatic star tracking. This method requires calibrating the position of the telescope first, the guiding process is complicated to operate, the interactive interface is unfriendly, and one should have much astronomical background knowledge to complete the operation.
The methods described above all need manual focus to get a good observation effect, it is trouble to operate when tracking celestial bodies or taking a long time exposure for photograph, and there is a high threshold for beginners so it will hinder the spread of astronomical observations.
Meanwhile, when taking the photos of the celestial bodies, a dedicated interface needs to be used to connect the camera to the eyepiece; it is not convenient for immediate viewing and network sharing.
In the prior art, a Chinese patent application with a publication number CN1808207A discloses an automatic finder control device for a portable astronomical telescope, using a main controller with microprocessor and the like, an equatorial drive controllers, GPS and DC motor, to control the telescope for pointing and tracking the target object. The device structure is complex, the main controller obtains data of stars stored in FLASH, using the information of time and location obtained from GPS, to deal with the calculations such as annual parallax calculation, solar parallax calculation, aberration calculation, calculation of precession, nutation calculation, and atmospheric refraction computing, the control process is complicated, and the device can not achieve automatically focus and photograph of celestial bodies.
A China Patent with a publication number CN101017240A discloses a video CCD auto guider method for an astronomical telescope, proposes to use the CCD for telescope auto guiding. However, in this method, the computer obtains video images by a video capture card, which means the telescope connects with the computer via wired connection, so it is typically used for the observatory and other fixed occasions, not suitable for using in mobile occasions by amateur astronomers. At the same time, this method also does not give an automatic focus method.
For ease of movement and control, a Chinese Utility Model with a publication number CN202334667U discloses an astronomical telescope automatic star finding and tracking device based on Android mobile phone control, using the Android phone to select objects to be observed on the touch screen, connected by WiFi to transfer a set of drive parameters to a control module, the control module controls the servo motor to rotate the telescope via the drive module to achieve star finding and tracking automatically. Although this means achieves a wireless control, and is easy to carry and use, but the device does not have the function of autofocus or the photograph of celestial bodies. If transferring the images via the WiFi in normal ways, the image data need for auto finding and auto focus is too large to transfer, it is difficult to achieve real-time image transmission and detection control.
In addition, the prior art lacks suitable auto focus method for portable astronomical observation system. As the distance of the celestial bodies is very large in astronomical observations, the focus method is different with such in conventional photography. The literature “An astronomical telescope automatic focusing system based on image definition evaluation” published in “Astronomical Research & Technology” 2008, 3, disclosed an automatic focusing method for telescope based on image definition evaluation. However, this method is only applicable to fixed stars, using only the near roundness and size of the stars as the basis for focusing, the relationship between the focusing function and the two parameters is not described, that is, the specific calculation method for focusing function is not given, and when using the method in focus searching, it is easy to fall into local maxima without finding the global optimum.
Therefore, a new automated astronomical observation system should be provided to accommodate the needs of amateur astronomers.