Image taken at 18mm are very distorted. This is why it is very difficult to platesolve this kind of image.
Also, even if platesolve was possible, imagine than you only have 3 or 4 pixels for a star. That means that photometry cannot be accurat.
In addition, your image presents a huge vignetted inverted. That means that your calibration is wrong. Photometry needs a flat image to give good results.