by Rex Parker, Director

Welcome to the Mid-Summer 2018 Edition of Sidereal Times, the official publication of the Amateur Astronomers Association of Princeton. We hope you’re enjoying the summer and getting a chance to do some astronomy as well. We’ll resume regular monthly meetings on Sept 11 at Peyton Hall, home of Princeton Astrophysics Dept. Meanwhile, we hope to see you at the AAAP Observatory at Washington Crossing State Park (see Observatory tab on the website).

Perseid Meteors (August 11-13). A few of us returned from the NEAF conference in April with out-of-this-world specimens – meteorites! At the Hayden Planetarium in NYC last week we marveled at the Willamette meteorite, the largest ever found in the USA (found near Portland OR) weighing in at 16 tons! The 50 gram specimen that I brought back from NEAF is a fragment of the Canyon Diablo meteorite (Meteor Crater AZ), whose ~30 tons explosively dispersed over a 9 km radius on impact thousands of years ago. Similar to the Hayden giant, the Diablo meteorite is mostly iron with ~7% nickel and 0.5% cobalt. The origin of the iron-nickel class can be traced to the cores of large asteroids and is similar in composition to earth’s core. In contrast, meteor showers originate from cometary material, and from spectroscopic studies appear to have the composition of carbonaceous chondrites. Of course only the rare large meteors make it all the way to the ground, whereas most are only a few grams in mass or even less. Despite low mass, the brilliant incandescence comes from very high kinetic energies with velocities on the order of 100,000 mph.

Meteor showers result from earth crossing the orbit of periodic comets, which over time have “leaked” small particles of dust and debris from the nucleus stretching out along the entire orbit. The Perseids are associated with comet Swift–Tuttle, which has a 133-year elliptical orbit crossing down through the earth’s orbital plane, most recently in 1992 (see Figure below, made using TheSkyX software). According to information provided by the American Meteor Society, most of the Perseid particles have been part of the Perseid meteor cloud for at least a thousand years, while a younger filament in the stream sometimes gives an early mini-peak the day before the main shower. This year the Perseid shower is predicted for the nights of August 11-12 and 12-13 and may reach 70 meteors per hour. The moon’s presence, along with earthly weather and light pollution, are the biggest factors in successfully seeing meteor showers. This year the timing of the Perseids is perfect with only a crescent moon setting early in the night well before the shower intensifies around midnight.

The Perseid meteors originate from the orbit of comet Swift-Tuttle which crosses the plane of earth’s orbit – we come closest on August 11-13. Image by RAP from TheSkyX software.

Mars Dust Storm. The planets have been perfectly positioned this summer for telescope observing. Venus, Jupiter, Saturn, and Mars are all readily accessible now from dusk to midnight. In June, I raised the prospect of top quality Mars observing – at AAAP observatory or wherever you may be – as the red planet approaches opposition (closest approach to earth, within 36 million miles, at the end of July). Unfortunately, the opposition has arrived with a major planet-wide dust-storm raging on Mars. This is bigger in scale than the storm portrayed in the movie “The Martian”, based on the best-selling book by Andy Weir. The dust-storm has obscured surface markings and even major geographic details such as the polar ice caps (not to mention the canals : >). All we can see through telescopes is the intense red color of Mars disk. There is still hope that the storm will abate while we are close to opposition, but there appears to be a correlation of large Martian dust storms and orbital position of the planet. As you’ve probably read, the NASA Mars rovers are affected. The atmosphere became so opaque with dust that Opportunity rover was shut down because its solar panels are unable to recharge batteries. Fortunately, Curiosity rover is powered by plutonium thermo-electricity and is not threatened.

Skynet – Remote Astro-Imaging for Members. AAAP continues to sponsor member access to remote astro-imaging through UNC-Chapel Hill’s Skynet robotic telescope network. The telescopes are located all over the world, typically 16” imaging scopes of Ritchey Chretien pedigree with high quality large format CCD cameras. AAAP has paid for member access to the system under a contract with UNC Astronomy Dept, extending through next June. If you’re a newer member and have not yet tried this out, send me an e-mail note to get set up (). Training videos are included and you do not need prior imaging experience to begin learning with Skynet! Full details are in the June 2017 issue of

Sidereal Times available on the website under Newsletter/Sidereal Times Archives). Also see UNC’s Skynet website, .

Announcement – Mark Your Calendar

Jersey StarQuest (Oct 5-6, 2018). Once again we’ll be hosting the Jersey StarQuest astronomy weekend at the Hope Conference and Renewal Center in north Jersey http://camphope.org. This is a fun, educational, and inspiring observing-oriented event for both Friday and Saturday nights at one of the best relatively dark sky locations in the state. The Hope Center is located just north of I-80 a few miles north of Jenny Jump forest, and offers clean bunkhouse accommodations or camping on-site, and a kitchen for cooking if desired. Restaurants are within a few minutes’ drive. If you’re experienced or just beginning, a new member or veteran, even if you don’t own a telescope, here’s your chance to learn hands-on about astronomy and observing.

• Walk-in registration, no advance payment or pre-registration needed. You can decide to attend at the last minute. We will ask that you send in a non-binding intent-to-participate form to help estimate needs for Hope Center.
• AAAP member-oriented event, a chance to make friends in the club. You’re also welcome to invite family and friends who may not yet be members.
• Low costs. The club subsidizes the costs, we do not make money on the event but the more people attend the better the economic outcome for the club.
• No meals will be provided. You should bring your own food and plates etc or plan to head out to restaurants about 10-15 min away. The Hope Center’s well equipped kitchen will be available.
• Hot and cold drinks and snacks (incl. coffee for staying up late) will be provided.