Parabolic Mirror Test

I played Ronchi Test for almost one week. First, I didn't get any pattern as I saw on website. Try a lot of different distance, still no sign.
Later, I read manual again, found a serious problem---no grating for source. All right, I added and found a clear view. Unfortunately, it looked so nice if I use my eyeball to see the mirror, it's terrible once after I use Ronchi Test and put image in the monitor.
I paged brad, he suggested I should use one single grating for source and monitor since bow lines may be caused by bending or misaligning two grating for source and monitor respectively.
I tried, however, still got same thing. I'm pretty sure it's not because of monitor lens since this time I use my eyes to see it.

Anyway, I will use webcam for this test tomorrow, so I can save the image on the computer and print.