Any way to allow an object to show through another in blender?

Is there a way to have an object (like a sun) show through another object (like the sky)? I don’t want to use over/underlay scenes, because I’ll already have three scenes layered (HUD, MAIN, SKY).

You could make your skybox object transparent (bottom of the materials window in the properties menu) enough to be able to see the sun, but that’s the only way I can think of to do that.
Have you considered putting your sun just inside your skybox?

Do you have a background scene already?

Place the sun object in the background scene inside of the skydome and use a script to rotate a static camera in the overlay scene to match the rotation of the main camera.

I wanted the sun behind the skydome (along with the moon). That way I can change the atmosphere’s transparency so the moon will become invisible during the day, but cause a solar eclipse when the moon is in front of the sun. MichelleSea has a good idea, and I might alter the moon transparency to help it become invisible when the day goes by. I may also try over-saturating the object colour channels.