Ceiling Stain

+1 for folex. Amazing stuff.

Try some Folex you can get it at Lowes and other places.

You may have to clean it a few times to get the stain out. It wicks from the inside to the outside until gone. Ammonia and water may lighten it. We recently had a small leak on a slide with a brown stain. We noticed it before it had a chance to dry and used a shop wet vac on it. It pulled all the brown out and no stain now. Maybe if you try cleaning again and while wet used a good shop vac to suck all the moisture back out and repeat as necessary you may get it out. Don't saturate it or the adhesive could let loose.

I had good luck with a small handheld steam cleaner and vacuum cleaner. Use distilled water to avoid crud in tap water. Maybe a very soft brush.

Without knowing how large a stain this might be in advance, you might build a decorative round piece of wood with the antenna crank hole in the middle, then put that on the ceiling to conceal the stain.