----- Original Message ----
> From: klauslms <[EMAIL PROTECTED]>
>
> Hello all!
> Is someone so kind and explain what major axis diameter
Major axis is the "long axis" of an ellipse, so this is length along the long
axis of the galaxy.
> at 25mag/arcsec2
More specifically, that's 25 magnitude per square arcsecond- a measure of
surface brightness.
Galaxies fade out gradually at the edge, so it can be hard to say exactly how
large they are (a longer exposure can make them look larger). So apparently
PGC is using 25mag/arcsec^2 as an arbitrary surface brightness level to define
the "edge", in order to specify the size.
-John
> (from PGC catalogue) means and if there is a connection
> to magnitude and size of the objekt and how to compute this?
> Kind regards
> Charly
>
