Upside down?

Dr Paul Leyland

I understand the reasoning behind why planetary images are generally shown “upside down” but (with one major exception) most everything else these days is displayed with north to the top and east to the left. Look at any major atlas, either on paper or on-line, and it will follow this convention. As far as I can tell, most images in the BAA gallery are similarly aligned though, to be sure, some are not but those exceptions seem to show no particular pattern.

My own images are generally N-up, E-left but that is primarily because that is the result of SWarp’s stacking algorithm rather than any conscious choice of mine. The raw subs are at whatever angle the camera happened to be at the time but a single sub is rarely of much use except perhaps for photometry where the angle and parity doesn’t matter for reporting purposes.

Now the major exception;: M31.  Images generally appear East-up & South-left or NE-up & SE-left. My favoured explanation is that some people prefer to see the galaxy in a landscape view rather than portrait. Hubble’s famous frontispiece to The Realm of the Galaxies adheres to the N-up & E-left convention.