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 is BAD for observing anything else - even the moon appears flat, washed out, and blinding. This is OK if you want to study the layout and geography of the Moon, but little else. The problem is this: the bigger the moon (more full), the brighter it is and that bright moonlight washes out all the other deep sky objects our visitors come to enjoy.

Generally, the less moon - the better.
  If you're going to pack up the kids and come out to Custer, aim for a night when the moon is a 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. 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.

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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