Right now me and my friend (i'm the artist producing the sprites and other visual assets for the game) are arguing over how to deal with a slight problem. Whenever we rotate a sprite the graphic engine drops pixels/etc I really don't know how it works but it ends up having this somewhat noticable shimmering effect.

Right now he is using opengl to handle all the engine related things. We have seen in other games like SPAZ (it happens to be a very similar game to our own in that it being about space ships top down) that the sprites don't really have any hard edges and nothing is sharp enough to really interpolate badly. Is there any particular method to deal with this with very sharp sprites in a game where you can zoom in and out as much as you like?

Here is one of our assets:
I hope this is the right place to post this sort of question. Sorry if I didn't explain clearly enough.