APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)

[Chris Peterson]

Astronomical images, by convention, should be presented with east counterclockwise from north. (And ideally with north up, but this convention is often ignored in order to match the geometry of the object to that of the camera, or sometimes for purely aesthetic ends.) This is what we see when we look at the sky, and what telescopes with an even number of reflective surfaces produce. Images presented with with east clockwise from north (as with today's APOD) are considered mirrored (and harder to work with).

What do you mean by east counterclockwise from north? Can you give me an example with a picture?

This is how I learnt it: In astronomical images, north should be up and east to the left.

Ann

That's the ideal presentation. But rotation isn't a big deal because images and charts still line up. Mirroring is what should be avoided, though. (Imagine driving with your GPS map. If the map isn't north up it probably isn't a problem. Indeed, many GPS maps are set up so that up is the direction you're traveling. But if it's mirrored? A left turn looks like a right turn on the map? That's not good!)