This paper studies the effect of ionospheric refraction upon auroral radar backscatter under conditions where the aspect angle appears far from ideal, i.e., when the unrefracted ray path trajectory is at least a few degrees from the perpendicular to the Earth's magnetic field. It is found that wave trapping by curved electron density layers can cause ionospheric refraction as large as 20¿, even at 150 MHz. This suggests that many so-called off-orthogonal VHF echoes are in reality due to backscattering at near-orthogonal aspect angles, the discrepancy arising from increased ionospheric refraction by curved or tilted layers. ¿ American Geophysical Union 1994