IMTS Insider

Small Manufacturing Device Makes a Galaxy of Difference for World’s Largest Telescopes

Category: IMTS Network Jul 10, 2020

By Kathy Keyes Webster, AMT Exhibitions Content Manager – Correspondence

When astronomers at the W.M. Keck Observatory on the island of Hawaii needed to be more accurate, they turned to HEIDENHAIN, a manufacturer of measurement and control products, for their ultra-precise sensors. Now Keck’s two 300-ton telescopes move to the accuracy of 10 nanometers! (A nanometer is one billionth of a meter. A human hair is approximately 80,000-100,000 nanometers wide1.)

IMTS exhibitor HEIDENHAIN has a long history of making state-of-the-art encoders, which are electromechanical sensing devices that provide information about position, count speed, and direction.

“The ultra-precise HEIDENHAIN optical tape encoders allow such a high level of accurate motion control that researchers are now able to gather data more accurately and quickly than ever before,” says Tomas Krasuski, the Lead Electronics Engineer at Keck Observatory. Krasuski was instrumental in the design and implementation of the telescopes upgrade project that began in 2009 and took nearly 10 years to complete without any downtime.

HEIDENHAIN’s ERA 84XX Tape Encoder

“We are now able to blindly point the telescopes to any star in the sky within Keck’s observable area with an accuracy of 1.0 arcsec. That is an accuracy level of one thirty-six hundredth of a one degree!”

“This is truly where the world of large and small meet,” said Krasuski. “To move these gigantic telescopes to the accuracy of 10 nanometers is absolutely amazing.”

Encoder Design Strategy
Keck Observatory’s Telescope Control System Upgrade project team worked closely with HEIDENHAIN engineers to develop a unique design that uses off-the-shelf, full circle HEIDENHAIN  tape encoders. The design team deviated from the traditional plan, which places optical encoder tapes on dedicated stationary rings at or near the diameter of the azimuth bearing. The team pursued a shorter encoder tape on a dedicated ring located near the center of the telescope axis. To dig into the details, visit HEIDENHAIN’S project description webpage.

W.M. Keck Observatory
The W.M. Keck Observatory atop Maunakea in Hawaii is a renowned astronomy center that features two of the world’s most scientifically productive optical and infrared telescopes with mirrors that are 10-meters in diameter. (For comparison, the diameter of the Hubble mirror is 2.4 meters, giving Keck a 17 times larger collecting area, allowing it to observe significantly fainter objects.)

W. M. Keck Observatory/Andrew Richard Hara

When scientists see interesting findings in other telescopes around the world, Keck is often used to confirm it. Keck has worked with other observatories to figure out more about the universe around us. Its top discoveries span anywhere from the Earth's solar system to the outer reaches of space. To learn about recent discoveries checkout Keck’s Cosmic Matters webpage.

Where else are encoders used?
Encoders are in many things we see and use daily. For example, encoders tell a controller within an elevator that it has reached the correct floor; give motion feedback to robots and cobots; indicate the exact pitch of a wind turbine blade or flood gate controls; and in a printer to activate a print head to create a mark at a specific location.

Have a story about how an encoder or another machine tool improved your project? Tell us about it at

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