Tick Labels for geo plots?

I’m using a scattergeo to mark locations on the celestial sphere for an astronomy application. The Mollweide projection while hiding the continents and showing the grid works well. The only shortcoming I’ve found is that I can’t seem to figure out how to add tick labels. It would be nice if the grid for this geo layout was able to display tick labels (lat and long) for at least some of the grid lines. Any ideas?