I cold not find any specific answer in SR5, but I could have missed it.
1. Could an Awakened character with the Summoning Skill and capable of Astral Projection, summon a spirit while in Astral?
2. If yes, since Conjuring can be perceived, as per Perceiving Magic (SR5, pages 280-281), what would the astral projecting character's body be doing to reveal the character is summoning a spirit? Would the body twitch? Would incoherent words escape their mouth? Would there be a visual indicator of mana, based on the Force of the spirit summoned?