[geuis]

I don't think that's right. The author clearly states its 0.004% of the sky, not 0.00004%. Simply adding a percent sign doesn't change the number.

[iclelland]

Yes it does, actually: "per cent" means "per 100", so, divide by 100.

50% is 50/100, or 0.5 of the whole

0.004% of the sky is 0.004/100, or 0.00004 of the whole sky.

[prophetjohn]

It's right. 0.004% == 0.00004

Just like 100% is equal to 1. If the image were 100% of the sky, you would divide by 1, not 100.

[tadfisher]

Yes, and 0.002 cents == $0.002.