Arc Seconds

[spudicus]

Hi All,

I've noticed a lot of planets are measured in arc seconds, for example Mars is currently 11 Arc Secs and in November will be 20 Arc Secs.

How do I actually wqork out what size that is???

Cheers

Spud

[Astroman]

An arc second is 1/60 of an arc minute, an arc minute is 1/60 of a degree and a degree is 1/360 of a circle. So, 360 degrees in a circle, 60 arc minutes in a degree and 60 arc seconds in an arc minute.

It refers to how large an object is against the sky. The Moon for instance subtends 30 arcminutes.