AGK3, SAO

Depends on the location of the image on the Schmidt plate:

0.2 acrcseconds (near the plate center)
to
1.0 arcsecond (near the plate edges)

Model: Chebyshev polynomiaL
Method: Least squares of of model using GSCP I

Overall quality: 0.15 mag

Average over all plate for objects far from the photometric calibrators: 0.3 mag