To work on companion tutorial for BOB Chapter 1 - Celestial Sphere

Contents include:

• WCS
• plot dist in different projections. alt/az, ra/dec, glat/glon
• proper motion, ephemeris
• observation planning tool
• some problem demonstrating cos dec issue

Whether there will be a narrative is to be determined. The initial workflow will be on Google Colab, and a link will be posted in this conversation later.