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> Procyon has the same diameter and brightness as Saturn. How could he possibly that have determined? I don't think that Brahe could measure this he hadn't eve
by chopin 7y ago
> Procyon has the same diameter and brightness as Saturn.
How could he possibly that have determined? I don't think that Brahe could measure this he hadn't even a telescope. The apparent diameter you see from stars is diffraction limited.
- antepodius 7y agoThey didn't know that, and assumed the apparent diameter was the true diameter (as you would).
- shadowprofile77 7y agoYes but diffraction of light wasn't understood at the time, or until a couple centuries later.
- anovikov 7y agoTycho was pre-telescope... so he had no idea that Saturn has a bigger visual diameter than Procyon... But, he could at least figure it out indirectly - by noticing that all stars twinkle a lot, while planets do not (or only a bit, on the worst nights).