There are two basic methods for astrophotography through telescopes-direct focus method (referred to as the direct focus method) and the magnified photography method (referred to as the magnification method). At this time, the telescope is best installed on an equatorial mount with an electric tracking function and a steady On a tripod.
- The magnification photography method
This is relatively simple, just use the camera to take a picture of the image in the eyepiece. Since the sun image is bright, this method is completely feasible for shooting the sun. We only need to visually make the image of the sun clear first, and then hold the digital camera and stick the lens to the eyepiece. At this time, the optical zoom of the digital camera itself should be placed at the widest angle end. Pay attention to fine-tuning the angle and direction of the lens to ensure that the lens and eyepiece are coaxial (the left hand can simultaneously pinch the camera lens and eyepiece to help them coaxial, as shown in Figure 1), then you will see the center of the LCD screen of the digital camera A round bright spot appears, which is the field of view of the eyepiece, and the dark part around it is the dark corner of the optical system. Then we use the optical zoom to slightly extend the focal length to expand the field of view and reduce the vignetting. When the sun is evenly displayed on the LCD screen, half-press the shutter, and the camera will usually focus automatically (sometimes you need to set the focus mode to macro mode to achieve autofocus). If the image is shaken due to the lack of features on the solar surface, or wind, it may cause the focus to fail. At this time, we can only use the camera’s manual focus function (if your camera does not have this function, there is no way).As for other shooting parameters, the white balance is recommended to be set to “daylight”, and the exposure parameters can be tried using the camera’s automatic gear (be sure to turn off the flash). If it does not meet the requirements, use the M gear to manually set it. If the telescope does not have an electric tracking device, the exposure time must be short to ensure that the sun does not drag the line on the photo (for example, shorter than 1/250 second). But the total brightness of the sun is limited, so you can only use a lower magnification (but too low magnification will lose a lot of details), or set a higher ISO (that is, the sensitivity, but the higher the sensitivity The more noise in the picture), how to find a balance among these parameters should be flexibly mastered according to the brightness of the sun at the time, the condition of the equipment in your hand, and your requirements for the picture.
- The direct focus method is relatively troublesome
To use this method, you must use a digital SLR camera. The lens of this camera can be removed. After removing it, remove the eyepiece of the telescope, and then connect the body of the DSLR to the main mirror of the telescope through an adapter ring. Together, this is equivalent to using a telescope directly as the lens of a camera. The advantage of this method is that the optical system that passes through is the least and simplest, so it can guarantee the best quality imaging-although the image obtained in this way is not as large as the magnification method. The most critical device of the direct focus method is the adapter that connects the camera and the telescope. This kind of adapter can be bought in astronomical equipment stores, but pay attention to the brand of the camera. Different brands of digital SLR have different interface models; also pay attention to the size of the telescope eyepiece port. Generally speaking, the common eyepiece end interface The size of the telescope is 1.25 inches, and some better telescopes use a large 2-inch interface, while the interface of an older model of a small telescope may be a small 1-inch interface.After connecting the camera to the back of the telescope, all you have to do is to use the camera’s viewfinder as an eyepiece, find the sun and use the telescope’s focusing device to adjust it clearly, then set the camera’s exposure mode to M, and set the sensitivity manually And the shutter value. Because the sun is very bright, the sensitivity can generally be set to the lowest, and the shutter speed can be used to find the most suitable value through real shooting and playback. If possible, it is best to use a shutter release or remote control to shoot, because pressing the shutter by hand may cause vibration and blur the picture.