processing method
Let me add that the imaging ring brightness of general optical systems
It is not uniform, but a gradational image with dark in the middle and bright around. Generally, when taking a single picture before, as long as the optical system is good enough
The peripheral dimming is not very serious, and the image quality is not critical, in fact, can be ignored, but now more and more people like to play multiple splicing
The peripheral dimming needs to be dealt with, or a large piece of cloth will be made. The method is to use a telescope to aim at objects with uniform light and take a few pictures, and then divide them evenly
Remove astronomical images. If you have only one telescope, use the same camera to shoot the flat field at the same focal length only once
In addition to the astronomical photography function, if you want to do magnitude measurement, you can measure the magnitude only after you finish leveling. (This material is quoted... so it is in traditional Chinese.)
PS: Some astronomical tools are equipped with flat field devices
1. PHOTOSHOP can be done, but it's troublesome
2. Metamorph image processing software can
3. There are similar in SAMPLE of ZEMAX
4. There is an example in the optical technical manual, which you can refer to. It reminds you that the seven piece model can achieve near theoretical value without FK2 to ensure good processability
