I am going to agree naming a son after a female deity is not a good route. I name similar to Juno is Juni, which i happen to like. I have no idea where the name comes from, except it appears as a character in Stone of Tears by Terry Goodkind. It is meant to be a masculine name, and sounds like a boys name to me. Mikel does sound a lot like Nikel. Jonathan, Daniel, and Jason are very common names, so if you are going for something unique, it might not be the path. Astro does remind me of the Jetsen's dog, along with Cosmo Crammer for some reason. I've never heard the name Ajel before, the closest thing is a weapon in the Terry Goodkind's booked called an Agiel. Which is only used by women, and causes immense pain, possibly killing a person. Why do want the name to be Christian? If your going to raise the child to be christian, does the religion of the name really matter, unless it is a name that condradicts something in the religion. I like the name Gavriel though, it is Christian and a boys name. Its the original hebrew form of Gabriel, an archangel. Zerachiel is a name of another archangel, and ive never seen this name used, and it doesnt come off wierd to me.
Perhaps look up names that would mean something to you, like a deffination of what you would like the name to mean. I know personal your son will ask why you choose that name, and 'just because' or 'some people on a forum liked it" might not go over well. Best of luck to you.