Plan your visit.

The Custer Institute and Observatory is Long Island's oldest public observatory (est.1927). Open to the public every Saturday evening from dusk until midnight, our staff of volunteers will give you a tour of the facilities and the night sky through our powerful telescopes.

Wait a minute - what do you mean "sunset", "dusk" and "dark"?
What time can we expect to observe?

First, the sky needs to be dark and clear, and then we need Custer Staff, which are all volunteers.

Custer is staffed with volunteers dedicated to astronomy and to the goal of educating people about the universe around them. We are either coming from work or some other engagement, need time to eat dinner, get to Custer, open up, settle in, and prepare for our visitors - and wait for dark. Saying we open at dusk or dark has, admittedly, been a little vague.

Sunset, which is the point at which the earth has rotated enough that the sun is no longer visible from the local horizon, but is still too bright for much observing. Dusk is the point where you need a light to read outside.  Dusk is the beginning of darkness in the evening and when when the earth has rotated enough that the center of the sun is at 6 below the local horizon. It just starts to get dark after this.

You can't see too much in the sky unless it's dark! You can see Venus, Mercury, or the Moon if they are up and visible - but not much else until its good and dark. This roughly translates as the following times when the observatory staff will be ready for visitors:

  • 7pm-midnight January - March
  • 8pm-midnight April
  • 9pm-midnight May - August
  • 8pm-midnight September
  • 7pm-midnight October - December

Some things to keep in mind when planning your visit to the Custer Observatory:

A Full Moon makes it difficult to see much else in the night sky. It can almost be blinding. Its a fine time to study the layout and geography of the Moon, but little else. If any of the brigher planets are visible, you can see them despite the bright moon. We always manage to have a good time.

Generally, the less moon - the better.
  If you're going to pack up the kids and come out to Custer for the night, aim for a night when the moon is half, crescent, or in New Moon phase. Check this moon calendar and aim for a darker week if possible. We want you to get the most out of your visit with us.

Clouds, rain, fog are BAD for optical astronomy (looking through a telescope). . The hopeful sounding, yet vague "partly cloudy" usually means poor viewing that night. Just because you can see a few stars through the clouds doesn't automatically mean it's a good night for observing. Looking at stars with a telescope really doesn't reveal too much more than what you see just by looking up at them naked eye. It is the deep sky objects, planets, and a sliver of the moon that satisfy most visitors. We can get them on a good observing night. (Radio Astronomy does work through clouds!)

To have a good observing night,
we need a dark, cloudless, non-hazy sky.

Don't forget to check our weather.


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