I'm planning on going to the John Glenn Astro park to take nighttime photos. That park closes at 11pm. Does the campground remain open so that I can get into my site after 11pm?

The park does not close at 11:00 p.m. It closes at dusk. However, John Glenn park is open during the night and that is the only area you can legally go into after dusk (barring the campground) and you have to actively be viewing astronomy to be there. You need to get on the John Glenn Astronomy Park FB page to get a ticket/register online to go there. If you are a registered camper, you can get back into the campground any time.

Campgrounds are open 24/7 at least that was how it was a month ago. Quite time around the camp ground is around 11pm

Campgrounds are usually open