Amateur Astronomers Association of Princeton

by Rex Parker, PhD
director@princetonastronomy.org 

Upcoming AAAP events.  We’re working on a variety of activities to make this the most accessible and fun year ever for astronomy in the AAAP.  In addition to the regular public meetings each month on the Princeton campus, here are a few upcoming events being planned for members to participate in. More detailed info will be forthcoming next month.

• Field trip to the US Naval Observatory in D.C. (spring)
• Members-only special night at Washington Crossing Observatory (spring)
• Regular public open house Friday nights at the Observatory (April-Oct)
• Observing weekend at the renowned astronomy dark sky site, Cherry Springs State Park in northern Pennsylvania (July)
• Easy road trip to see the famed Bell Labs Horn Antenna, Holmdel NJ, where the cosmic microwave radiation was first discovered (summer)

The recent AAAP tour of Princeton Plasma Physics Lab was a hit, with  about 25 members participating in a private, behind-the-scenes look at the leading U.S. center for fusion energy and plasma physics research (see PPPL article and photos elsewhere in this issue).

Beware the Ides of March? From history and the arts, a sense of danger accompanies the phrase “beware the Ides of March”.  Back in 44BC, Julius Caesar was forewarned by a seer that he’d come to harm not later than the Ides of March, a prophecy which came to pass and drastically changed the Roman Republic.  Okay, admittedly I’ve not seen Shakespeare’s “Julius Caesar” where the famous line is spoken, but at least have met his heir Octavius in “Antony and Cleopatra” at McCarter this winter.  The Roman calendar was based on moon phases with the Ides occurring at mid-month (day 15 for March) corresponding to the full moon.  So really the Ides of March no longer casts a foreboding spell but announces the end of winter and rebirth of spring with the coming equinox!

Spring is galaxy season.  With the equinox, we can begin getting outdoors again in both day and night.  More galaxies can be seen in moderately-sized telescopes in spring than any other season, with the incredibly dense galaxy clusters in Virgo leading the pack. If you’ve never seen a galaxy through the eyepiece of a good telescope, this spring will be a great opportunity to try it.  Upgrades now underway at AAAP’s Washington Crossing Observatory from our recent equipment acquisition and video astronomy technology project will make it even more fun.  We hope that recent and long-time members will come out to experience the celestial wonders “hands-on” this spring.  Those interested in learning to use the equipment for your own studies and to be a part of our extensive public outreach programs are urged to attend the regular meetings and talk to Observatory co-chairs, Gene Ramsey and Dave & Jennifer Skitt to develop a plan for your training (e-mail:  observatory@princetonastronomy.org).

Should AAAP join the Night Sky Network?  Here’s an opportunity for AAAP to join a national organization of affiliated astronomy clubs with connections to NASA/JPL.  The Night Sky Network is a coalition of amateur astronomy clubs designed to bring astronomy and the excitement of NASA missions to communities. Applying for club (free) membership can bring several benefits that are described on the Network website, https://nightsky.jpl.nasa.gov/index.cfm.  The Network is a partnership of amateur astronomy clubs, the Astronomical Society of the Pacific, and other organizations.  The goal is to help amateur astronomers share knowledge, time and telescopes to bring amazing and emerging aspects of astronomy to the public. Ongoing research by the Astronomical Society of the Pacific and the Institute for Learning Innovation shows that amateur astronomers need and desire support of their outreach efforts. The Night Sky Network was inaugurated and has been expanded to help meet these needs.  Please browse their website, and we can discuss it at the AAAP meeting on March 10.

Messier-106, a Seyfert galaxy in Canes Venatici. Image taken by Rex Parker in Titusville NJ. Equipment: SXVR-M25C camera, AG Optical 12.5-inch Dall-Kirkham astrograph, Paramount-MX mount. Processed in Maxim DL v.5 and PS-CS5.

Color in the deep sky — under New Jersey skies? The beautiful intense colors in astrophotos of the Messier and other deep sky objects, with glowing reds and blue-greens emitted by vast ionized hydrogen and oxygen gas clouds among the stars, have become familiar sights on NASA and Hubble internet sites and in those big glossy coffee table books. Galaxies also emit intense light energy in the violet, blue, and red bands due to numerous regions where young stars are being born (the H-II regions). But the deep sky color pallet is actually quite subtle and almost never visible in a telescope eyepiece due to the limits of human eye physiology and the faintness of the light captured by the telescope.  We rely on CCD imaging techniques which fortunately have advanced remarkably over the past 15 years or so.

Experts, often working in high altitude desert locations with very dark skies, usually approach color astro-imaging using the “LRGB” method.  Here many subframes are taken over the course of several hours with a high sensitivity monochrome CCD through a telescope using a sequence of color filters (Luminance, Red, Green, Blue = LRGB).  The individual filtered subframes are then calibrated and combined and balanced in the computer to create the final color images.  Here in central Jersey our less-than-pristine skies introduce serious challenges even with top-notch equipment.  Moon and skyglow backgrounds along with light pollution gradients conspire with changing weather, humidity, and seeing conditions over the course of a single New Jersey night, often introducing nearly intractable noise and light gradients in the LRGB-derived images.

NGC4631, the “Whale Galaxy” in Coma Bernices. Image by Rex Parker, taken in Titusville NJ. Equipment: SXVR-M25C camera, AG Optical 12.5-inch Dall-Kirkham astrograph, Paramount-MX mount. Processed in Maxim DL v.5 and PS-CS5.

But there is hope for New Jersey astronomers!  Whether you are considering astrophotography, or are already on the learning curve, you don’t necessarily have to buy that remote property or telescope time-share in the desert southwest.  After more than 12 years using the LRGB imaging method, I began to consider whether a “one-shot color” astronomical CCD camera would potentially produce better results under New Jersey skies.  The much reduced hardware complexity and lower weight and telescope balancing issues with one-shot color cameras add to their potential attractiveness over the LRGB technology.  The one-shot color approach uses a CCD sensor with a Bayer-matrix of RGB filters directly on the sensor itself (like terrestrial DSLR cameras). Once acquired the images are “de-Bayered” to convert to color using software after many subframes are calibrated and stacked.  The idea of using a one-shot color camera disputes much of the expert advice out there, which warns that these cameras are unsuited to light-polluted areas.  I wanted to test whether this was true, and theorized that the ability to capture all colors simultaneously in each subframe could actually minimize the noise/gradient issues which change over the course of an imaging run here in New Jersey. Further, it is proposed that the final resolution could equal that of the LRGB method if the image scale is appropriately selected (that is, CCD pixel dimensions must be carefully matched to telescope focal length).

Perhaps it should have been obvious that testing this hypothesis during winter would mean working in near-zero temperatures – that slowed things down a bit for me! The images above are a couple of first attempts (from February) to see color in galaxies imaged from central New Jersey using the one-shot color CCD method. The plan going forward is to make comparisons of both color approaches for a variety of deep sky objects, to determine if the one-shot color method is truly a better option than LRGB for our local sky conditions.