If you saw my other question, well, there is still a little problem:
Basically, the frame rate is very bad on the actual device, where for some reason the animation is scaled (it looks like the left side on the video). It is quite fast on the simulator where it is not scaled (right side).
For a test, I submitted this new changeset that simply hard-codes the smaller size (in SDL_CreateWindow() and in glViewport()), and as you see in the video, now it is slow even in the simulator (left side shows the small size, right side shows the original size -- otherwise the code is the same).
I'm clueless why it's soooo slow with a smaller galaxy, in fact it should be FASTER.
The question is not about general speed optimization like reducing screen resolution or joining glBegin(GL_POINTS)/glEnd() blocks.
Update: For a test, I simply reduced the screen size to 320x480 and compiled it to OS X desktop -- got the same speed as with 800x800, so this size-specific slow-down is on iOS only. Will post this on the SDL mailing list now.