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Friends Tour Mauna Kea Observatories

by Cheryl Ernst

Subaru Tour>

Friends of the Institute of Astronomy toured Subaru Telescope. Photo by IfA Friend Maria Lowder.

One of the remarkable things about the Friends of IfA field trip to Mauna Kea was how much the professional astronomers enjoyed not only sharing their knowledge, but also participating in our activities.

"I've only done this once, and I was blown away," our coordinator, Robert Jedicke, confided when describing our upcoming opportunity to look through an eyepiece mounted on a major telescope at the summit.

This trip was about getting up close to the remarkable tools involved in making discoveries from Earth's best astronomical vantage point, despite the potential discomforts associated with thin air, crisp temperatures, and winding roads. After a tour of the IfA Hilo building and the Subaru Telescope base facility, and a tasty lunch at the new `Imiloa Astronomy Center in Hilo, we headed for Hale Pohaku, the mid-level complex that provides accommodations for those working on the mountain. While our bodies acclimatized to the altitude, IfA personnel continued to enrich our minds.

IfA Associate Director Klaus-Werner Hodapp provided a brief history of the evolution of the telescope, from the human eye ("a pretty decent optical system, but with limited spectrum and only about 1 percent efficiency") to modern CCD devices, with their wide range and near 100 percent efficiency. Like so many modern inventions, early telescope technology was developed first for military use and then adapted for scientific research. Crude as his telescope was, Galileo identified the four brightest moons orbiting Jupiter. Newton developed a reflecting telescope. By the 19th century, the science community was building some good telescopes.

Astronomer Bo Reipurth explained how telescopes are nothing more than "light buckets"; photons (particles of light) are collected much like water drops in a rain gauge. Instrumentation is nothing more than the measurement and analysis of the "light drops" collected.

With CCDs, or charge-coupled devices, photons are converted to charged electrons, which can be measured digitally. These light-sensitive silicon chips are a hundred times more sensitive than a photographic plate, making them a vast improvement over photos astronomers used to pore over, according to Colin Aspin, who manages the UH 2.2-meter (88-inch) telescope. Think of an astronomical CCD as your digital camera on steroids, capable of images 4,000 pixels squared.

What do scientists do with all those pixels? For every night of viewing, they may spend two months analyzing the raw numbers, removing the "noise" of the instrument's signature and atmospheric interference, and calibrating the data to standards as they measure the astrometry (location), photometry (intensity), spectrometry (wavelength), and polarimetry (optical properties) of the bodies observed, explained astronomer Bobby Bus. Postdoctoral researcher Josh Walawender described how such observations have yielded information about the formation of stars deep inside the dark clouds of gas and dust that are the raw materials of star birth.

2.2-meter telescope control room

Friends in the control room of the UH 2.2-meter telescope prior to using the telescope for a night of observing scheduled just for them. Photo by IfA Friend Maria Lowder.

Then it was on to the summit and a tour of the 8-meter (27-foot) Subaru Telescope. Failing light and falling temperatures signaled the main event. After admiring the spectacular sunset, we took turns viewing the night sky by eye, portable telescope, and the UH 2.2-meter telescope. Imagine the Moon so distinct you can make out shadows cast by craters and the mounds within. Imagine a Jupiter so large and bright that after observing the shadow of a passing moon, you are temporarily night-blind when you step back from the eyepiece.

Imagine … or go on the next field trip and see it for yourself. Next year's trip will be to Haleakala Observatories.

Cheryl Ernst is a Friend of the IfA and creative services director within UH External Affairs and University Relations.


To become a member of the Friends of the Institute for Astronomy, call the Friends line (808) 956-6665 or e-mail  For online information, see