Following the Footsteps

Pereira spends about 1½ hours each clear night (regardless of the Moon's phase) searching for novae. With three visual finds, he follows in the footsteps of the world's two greatest visual nova discoverers — the late George E. D. Alcock of Peterborough, England, and Peter Collins, "the George Alcock of the Americas." Alcock has made five nova discoveries and Collins four.

Like Collins and Alcock, Pereira doesn't rely on traditional star charts to check for novae. Instead he creates his own mini-constellations out of the stars he sees with binoculars and then memorizes their patterns. Alcock pioneered the "mini-constellation" technique decades ago; beginning in the 1950s, he memorized the Milky Way star fields down to about 8th magnitude as seen through 40- and 80-millimeter binoculars. "This stands as one of the great observational feats of the 20th century," says Collins.

To date, Pereira has memorized fields in about 14 constellations. Depending on the richness of the star regions, he searches to either magnitude 7.5 or 9.0. His entire hunting grounds cover some 2,000 square degrees of sky along the plane of the Milky Way, and he has the positions of more than 3,000 stars memorized. If fate continues to shine favorably on Pereira, the 37-year-old amateur has the potential to become the greatest visual nova discoverer of all time.

New Stars on Film

Despite the outstanding efforts and successes of visual hunters like Pereira and others, the preferred way for amateurs to discover novae is through photographic searches. And the most successful photographic nova hunter in the last decade has been William Liller of Viña del Mar, Chile. Using little more than a 35-mm camera, an 85-mm lens, Kodak Technical Pan 2415 film, and an orange filter, this 74-year-old professional-turned-amateur has discovered nearly two dozen novae — the most recent being a discovery on March 3, 2002, in the Large Magellanic Cloud.

The success of Liller's program — aside from his desire to photograph the Milky Way whenever possible — can be attributed to his use of a homemade, 25-power stereo viewer. One eye looks at the new sky photograph; the other at an archival image. When a star appears in one image but not the other, further investigation is required.

Other searchers use a blink comparator, a device that allows them to display in quick succession two alternating images of the same field taken at different times. The process is called "blinking" because if a nova erupts, its image appears to "blink" in and out of view. Although electronic images taken with CCD cameras can also be blinked on a computer monitor, many nova hunters still prefer a camera and film over CCDs for two reasons: first, a photographic camera lets them record large areas of the sky at one exposure, and second, the cost of film and processing is negligible compared to that of a CCD camera and its ancillary equipment.

Blinking films has been undeniably effective. Besides Liller, a handful of other photographic nova hunters have risen to fame in recent years. Since 1990 Paul Camilleri (Cobram, Victoria, Australia) has discovered nine novae with an 85-mm lens, and several Japanese amateurs have discovered in total some 20 novae. Top among them is Minoru Yamamoto (Okazaki, Aichi, Japan), who has used a 200-mm f/4 lens and Kodak T-Max 400 film to discover six novae.