S top or N top

Martin Lewis

Hi Peter,
It’s good to have a convention to make images easier to compare images and can’t see a reason not to stick with the existing arbitary one rather than change it after several centuries. Jupiter with a GRS at the bottom and a Mars with Syrtis Major at the bottom – to me they just don’t look right.

It is arbitary whether it has been chosen to be north up or south up but south up is the existing astronomical convention. In the northern hemisphere that’s the view in an inverting telescope but from the southern hemisphere that is the view in an non-inverting set up. There is no such thing as the right way up or wrong way up just the conventional way up and the unconventional way up.

I am intruiged by your comment that you see visually a view with North at the top when you view through an SCT with no diagonal. Surely an SCT with two mirrors should give an inverted view. I though it was only through a diagonal that  you would get a non-inverted view but it would be mirrored L-R.

Cheers, Martin