Problems:

1.Size of diffraction image

2.Ross effect (shrinking of high exposed star images in the photographic emulsion)

3.Halo by diffusion of light in the photographic emulsion

4. Scintillation

Methods of improving the observation conditions are as following:

1.Deformation of diffraction image with quadratic or other formed masks

2.Diffraction gratings render possible a better measurement but don’t avoid Ross effect and halo of diffusion.

The halo of diffusion can reach much more of diameter than the original image.