# What is the meaning of a negative Galactic longitude?

What is the meaning of negative longitude in Galactic coordinate system, for instance in this article? Does the longitude $-65^\circ$ equal $295^\circ$?

Yes, this is usually what is meant by a negative longitude, it's just a convenient way to express a range that happens to straddle the zero-point. And in the context of the HiGAL survey you were looking at, this is precisely what is meant.

• If you add the source to your question and add a comment here (so that I notice) I can have a look. Commented Jun 30, 2016 at 3:50
• I don't know if this is what he refers, but the Galactic Coordinate System does mention negative declination on Wikipedia: en.wikipedia.org/wiki/Galactic_coordinate_system Commented Jun 30, 2016 at 4:39
• @userLTK Declination is not the Galactic coordinate system, and it's a latitude coordinate, not a longitude. It runs from $-90^\circ$ to $+90^\circ$. Commented Jun 30, 2016 at 6:14
• I was going through the documents of HiGAL survey of Herschel. It says that the HiGAL surveys the longitude range, -65<l<65 and latitude b<=|1| .
– Rian
Commented Jun 30, 2016 at 14:58