Image Processing Reference
for higher-order aberrations. However, this system laid the groundwork for more
experiments in the area.
The astronomical observatories at Mauna Kea, Hawaii, all enjoy the excellent
astronomical seeing at the site. For many astronomers who worked on Mauna Kea,
the seeing was so good that it drove them to explore different ways to further im-
prove the performance of their telescopes. This quest led to the development of the
first modern tip-tilt systems to correct for low-order image motion. Thompson and
Ryerson (1983) reported on the success of the ISIS (image stabilizing instrument
system) tip-tilt system used on the Cassegrain foci of the University of Hawaii 2.2
m as well as the CFHT 3.6-m telescope. While ISIS was the first reported tip-tilt
system at the Mauna Kea Observatory, other researchers at CFHT began work on
the high-resolution camera (HRCam) (McClure et al. 1989).
For astronomical image stabilization, the most common systems are of the
moving mirror or moving lens type. Both ISIS and HRCam used a moving mirror
and sensor system to provide image stabilization. This system provided significant
correction of atmospheric and telescope-induced jitter in the final focal plane,
while maintaining very high light throughput. Corrections were measured down to
about 0.5 arcsec with this system.
The following sections contain a partial list of active projects that use im-
age-stabilization systems and more advanced adaptive optics systems.
7.3 Programs Using Image Stabilization
Image-stabilization systems are an integral part of both natural and laser guide star
adaptive optics systems. In addition, many telescopes use sophisticated pointing
and tracking or autoguiding systems that have incorporated image stabilization
through mechanical control of the telescope. Observatories and telescopes with im-
age correction systems are listed in alphabetical order, followed by references to
more information about that facility. Many of these facilities have excellent Web
sites. Typically, the Web site can be easily located by entering the name of the facil-
ity in an Internet search engine. Internet addresses are not provided here as they
tend change over time.
Calar Alto Observatory
The Calar Alto Observatory, located in the Sierra de los Filabres in the province of
Almeria, Spain, is operated by the Max Planck Institute. The observatory has three
primary telescopes with apertures of 1.2, 2.2, and 3.5 meters at an altitude of 2168
meters. A 1.5-m telescope is hosted on the site and operated by the Madrid Obser-
vatory. The 3.5-m telescope is equipped with a laser guide star adaptive optics sys-
tem known as ALFA (adaptive optics with a laser for astronomy), which uses a sep-
arate tip-tilt mirror in addition to a high-order corrector.