How big would the apophis asteroid appear to us like in relation to how we see the moon?
If my memory serves me, Apophis is ~300 meters in diameter and at closest approach it will be ~30,000km away. So its angular dimension will be 0.300/30,000=1/100,000 Radians, which when multiplied by (180/pi)X3600=~2 arc seconds. Since the resolution of the human eye is ~1 arc minute or 60 arc seconds, Apophis will not show a disk to the naked eye, but will instead be “starlike”, which is what the word “asteroid” means, anyway. However, a good large aperture amateur telescope in good seeing has a resolution as low as 0.4 arc seconds at maximum magnification, producing an image of ~5-6 pixels across, allowing the resolution of some minimal amount of detail. The Hubble Space telescope and the best professional ground-based telescopes using atmospheric adaptive optics can achieve a resolution of ~0.01 arc seconds, allowing an image of ~200 pixels across, which will be quite impressive and unprecedented for the Earthbound imaging of a smallish asteroid. P.S. Extending my rough calculations
