Angular Dimension

No, angular dimension is not some alternate reality nor is is a bad new wave 80's band. Angular dimension is the measured size of an object in the sky as expressed, typically, in arcseconds or degrees. In english, "How big does it look in the sky?"

One of the hard things to express to groups sometimes is how big or small stuff is in the sky. A great example is the Andromeda Galaxy. It is 2.5 million light years away and 220,000 light-years wide but how big does it look to us? It is one thing for me to say that is it somewhere around two to three degrees wide but even better to compare it to something we know.

I've often told groups that the moon is only 1/2 a degree wide so they can imagine how big Andromeda would look if only it appeared brighter in our sky.

I wish I always had this photo on hand to show them. Wow.