Rittenhouse Astronomical Society

Rittenhouse Astronomical Society RAS was founded in 1888. Considered the oldest astronomy society in the country. Our monthly events feature guest speakers, planet and rocket reports, and more!

We hold live events each month along with occasional zoom meetings, and open houses at the Ryan☀️ observatory. Named for early American astronomer David Rittenhouse, RAS offers all interested persons an opportunity to participate in the activities of an astronomical group. Under normal circumstances, the Society meets monthly at the Franklin Institute in Philadelphia and conducts public events at

Ryan Observatory at Muddy Run in Holtwood, PA, but for the duration of the Covid-19 pandemic we will meet over Zoom.

08/12/2026
08/12/2026

Provided that you have clear skies this evening.... you're in for a show! The Perseid meteor shower peaks tonight. Best viewing time is between midnight and predawn. Make sure to stay away from city lights, dark adapt and enjoy! Wishing you clear skies!

07/20/2026

One giant leap for mankind

History was made on July 20, 1969, when Apollo 11's Neil Armstrong and Buzz Aldrin became the first to set foot on the Moon.

For more than 5 decades, the total number of moonwalkers has remained at 12. NASA will change that with Artemis IV.

06/29/2026

Who's excited for tonight's Strawberry moon! You're going to want to head out as the sun is setting. In the suns fading light you can still see Venus and Jupiter as they set. Looking eastward the strawberry moon will rise as the sun slips away. (You'll see it in about 15 minutes) The strawberry moon is named such, as this moon signaled the time to harvest berries. It won't actually be pink but as it rises it may exhibit a rosey hue, golden tones will be evident. This is caused by Earth's atmosphere, pollution ect. If you're trying some photography remember to drop your exposure down for best views. You may have heard that this is a micro moon. That is because the moon will be at it's furtherest point away from earth in its orbit. Don't worry....you won't notice. Another interesting fact is that it will be in the area of the center of our milky way galaxy. So know as you gaze upon it, you're also looking twords the center of our galaxy! Have fun tonight! Wishing you all clear skies and as always Keep looking up!

Now that the planets are further apart, it's a great time to watch the moon. It looks like the Tortiose from the Ryan Ob...
06/26/2026

Now that the planets are further apart, it's a great time to watch the moon. It looks like the Tortiose from the Ryan Observatory is doing just that, and he's got a great reason. Are you celebrating Moon Joy June?

Wishing you clear skies. Illustration from Sky and telescope.
06/17/2026

Wishing you clear skies. Illustration from Sky and telescope.

06/16/2026

Keep an eye out tonight after sunset. Venus and Jupiter will still be visible in western skies.

06/09/2026

If clouds got in your way last night not to worry. The great thing about conjunctions is that you have more then one chance! Try again tonight. Same time, same place. Wishing you clear skies.

06/08/2026

We may have missed out on the northern lights but take a look tonight. What are those eyes in the western sky? Venus and Jupiter! A Beautiful conjunction indeed! You'll be able to see them pair up until the 10th, but you'll want to head early for this one. You'll want to catch them before they dip below the horizon. About a half an hour after sunset is a good bet. Full disclaimer...clouds could happen...but I hope they aren't where you are! Happy viewing!

06/04/2026

Head outside tonight around sunset. Look northwards and use your cell phone camera to scan the skies. Remember your camera can see things that you may not be able to see visually. There is a very good chance tonight to see the Aurora ( northern lights) in our area. Good luck!

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Philadelphia, PA
19103

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