NCU Lu-Lin Observatory
Tsay, Alfred Bing-Chih Chen,
Kuang-Hsiang Chang and Huan-Hsin Li
of Astronomy, National Central University,
Taiwan 32054, ROC
The NCU (National Central University) Lu-Lin Observatory is located at
Mt. Front Lu-Lin, 120o 52' 25" E and 23o 28' 07"
N, a 2862-m peak (Fig. 1) in the Yu-Shan National Park. The construction of
Lu-Lin Observatory was finished on January 14, 1999. The initial study of Lu-Lin
site was started since late 1989. Later on, a three-year project was founded by
the National Science Council (NSC) to support the development of a modern seeing
monitor for this site survey study from 1990 through 1993. The average seeing of
Lu-Lin site is about 1.39 arc-second with average 200 clear nights annually. The
sky background of this site is 20.72 mag/arcsec2 in V band and 21.22
mag/arcsec2 in B band.
The Lu-Lin observatory is developed for both research and education
activity. A homemade 76-cm Super Light Telescope (SLT) and three TAOS's 50-cm
robotic telescopes will be the two major research facilities. We are proposing a
pilot program to perform SLT observations of time-varying astrophysical objects
exploiting the unique geophysical location (e.g. time and longitudinal coverage)
of Taiwan at the Western Pacific Rim in such topics of emerging interest. The
TAOS #1 telescope was installed at Lu-Lin in late March of 2000, while the other
two will be installed in late 2001 for the survey work of Kuiper Belt Objects. A
90 KW/240 VAC power line and a water pipe system have been pulled to this remote
site in early 2001 (Fig. 2). A wireless Network system through A-Li Shan has
been operated at Lu-Lin Observatory while a faster wireless Network system with
11.5 Mbit/sec bandwidth is under designing and will be available in the near
1: Lu-Lin site. Mt. Front Lu-Lin (2862 m) located in the Yu-Shan National Park,
has a relative flat summit for developing astronomical facilities.
2: Lu-Lin Observatory. The SLT is housed in the 6-m dome shown on the left hand
side. TAOS #1 telescope is on the right had side. The green channel
contains power line, water pipe and local Network cable.
NCU started the first site survey for a modern observatory in Taiwan since 1989.
The original plan was trying to move the NCU 24" telescope from campus to a
suitable site at the central high mountain range of Taiwan. Weather station data
and infrared satellite cloud cover data of Taiwan were studied to pre-select
potential sites (Table 1) for further investigation.
1: Potential Sites for Taiwan Optical Telescope
Mt. Front Lu-Lin
Mt. Small Snow site #1 2550
Mt. Small Snow site #2 2990
Among those potential sites, Mt. Front Lu-Lin [2862 m, (Fig. 1) hereafter
referred as Lu-Lin, located within the vast region of the Yu-Shan (Mt. Jade)
National Park and Forest Reservation, about five-hours driving from the home
institution - Chung-Li] been considered with a relative flat summit and
convenient transportation, was selected for a three-years seeing study.
is a special term of astronomy describing the phenomena of stellar image
broadening observed from the ground. When
a stellar image is observed through a ground-based telescope with high power
magnification, the observed image shape usually does not correspond with the
theoretical diffraction pattern of that telescope, but looks like formed by many
"speckles". Instead, the
diffraction ring may be resolved only partly or not at all, and an irregular
motion of the image is often observed. The phenomena of image structure
distortion and image motion may vary considerably with time and with the
location of the observer. These random displacements of part or all of the light
received by the telescope are called "seeing".
Astronomers use the envelope diameter of the first order speckles to
define the visible seeing α,
= 2 * 105 (λ／ro)
is in unit of arc-second, λ
is in unit of μm
, ro is in unit of cm and called the Fried parameter (Fried 1965,
1966), defined as the coherence
radius of the wave-front distorted by the turbulent atmosphere. The Fried
parameter ro is thus a function of the turbulence, the refractive
index, the wavelength of the transmitted light, and the air-mass above the
telescope. Typically at a really good site, the visible seeing, α,
is about one arc-second or less.
Seeing has been considered as the utmost importance factor for most
observations (Woolf 1982). From direct imaging, spectroscopy, and photometry, to
interferometric observations, seeing determines spatial resolution, limiting
magnitude and instrument speed. There are many methods for studying seeing such
as direct visual estimates, star trailing, high-speed photoelectric image
scanning, monitoring of differential image motion and image profile width,
speckle interferometry plus pupil imaging, and shearing interferometry (Ardeberg
For the Lu-Lin site survey, we designed a portable optical seeing monitor
which adapted a Celestron C-14 telescope mounted on Takashi NJP equatorial mount
and a high-sensitivity CCD TV-camera (Philips Amprex NXA 1031/01) as detector
(Fig. 3). This seeing monitor recorded the real-time images of objective stars.
The profiles of these stellar images were then analyzed by an IBM-AT/compatible
clone equipped with a video digitizer board at high speed (~ 1/30 sec). After
three-years seeing study at Lu-Lin site, we concluded the average seeing to be
about 1.39 ±0.34
arc-second, which is according to 757 CCD observations of 682 single star and
75 binary star measurements (Fig. 4 & Fig. 5 ). The annual clear nights at
Lu-Lin are about 200 nights. The sky background of this site is 20.72 mag/arcsec2
in V band and 21.22 mag/arcsec2 in B band carried out from ST-6 CCD
3: Seeing observation
4: Binary star – Castor – measurements.
average seeing of Lu-Lin
site is about
Lu-Lin site, located within the vast region of the Yu-Shan National Park
and Forest Reservation, was studied since late 1989. Further contact with the
Yu-Shan National Park, Ministration of Interiors and the Bureau of Taiwan Forest
took about one year to get the permission of constructing a site survey station
within 100 square meters land on the Lu-Lin summit. Since there was no exiting
driving access to Lu-Lin site, all construction material of site survey station
and survey instruments must be carried up by manpower from the foot to the
summit (Fig. 6). The observing station was first finished in 1991. With no
electrical utility, power supply for all equipments were coming from a generator
during the observation.
6: Survey instruments must be carried up by manpower from the foot to the summit.
After the site survey completed in 1993, the NCU proposed to develop the
Lu-Lin site for a medium size 2-m telescope observatory. We continued to propose
a feasibility study project of constructing a 2-m class telescope.
Following with the requirement of constructing medium size telescope
observatory, the NCU continually rent 300 square meters on the summit of Lu-Lin
for observatory (Fig. 7) and 500 square meters at the foot of Lu-Lin for remote
control center and machine shop.
flat summit of Lu-Lin site.
Until late 1997, a founding from NSC supported the
development of Lu-Lin observatory. A 6-m dome was built for a homemade 76 cm
reflector. The construction of Lu-Lin observatory was finished on January 14,
1999. After then, we started to contact the electrical power company. A 3.3 km
underground electrical power line to the foot of Lu-Lin in the national park
area was built by late 2000. Further electrical power line extended from the
root to the summit of Lu-Lin was installed in early 2001 with funding from the
MoE Excellency project. The TAOS #1 telescope was installed at Lu-Lin in late
March of 2000, while the other two will be installed in late 2001 for the survey
work of Kuiper Belt Objects. Another 50 cm telescope (similar to TAOS telescope
) from Yonsei University, South Korea is planning to join TAOS’s project as
the TAOS #4 telescope.
with the funding of MoE 4-year Excellency project, a 90 KW/240 VAC power line
and a water pipe system can be pulled up to this remote site in early 2001. Also
a wireless Network system through A-Li Shan has been operated at Lu-Lin
Observatory, while a faster wireless Network system with 11.5 Mbit/sec bandwidth
is under designing and will be build up for the near future remote observation.
Lu-Lin observatory is developed for both research and education activity. The
homemade Super-Light Telescope (SLT, Fig. 8), adopted a 76-cm diameter HEXTEK
Honey Comb lightweight gas-fusion mirror, is expected to be fully operated in
the fall of 1999. The maximum field of view (FOV) of SLT, with fast primary
focus (f/1.8) and Ritchey-Chretien focal ratio (f/9) and plate scale around
approaches half-degree square. In the first phase, only one quarter of the FOV
will be used with an Apogee AP-8 thin CCD ( 1K x 1K , 24μm/pixel).
We are proposing a pilot program to perform the SLT observations of time-varying
astrophysical objects exploiting the unique geophysical location (e.g. time and
longitudinal coverage) of Taiwan at the Western Pacific Rim in such topics of
homemade 76 cm Super Light Telescope (SLT).
The Taiwan-American Occultation Survey (TAOS, Chen et al. 1999) is a
collaborative project to conduct a census of comet nuclei in the outer solar
system. The TAOS experiment will initially consist of three 50 cm, wide field
(f/1.9), robotic telescopes, each equipped with a 2K * 2K CCD camera. In the
first phase, the three TAOS’s telescopes will be installed at NCU Lu-Lin site
(2862 m) by the end of 1999 (Fig. 9). A year later, one of the three telescope
will be moved to the West Peak of Jade Mountain (3450 m) with a 6 km base line
in the east-west configuration. This experiment provides the only means to study
the cometary population in the small sized end of the distribution. A great
number of scientific products, notably variable stars, will also derive from the
huge TAOS database.
TAOS # 1 robotic telescope.
With a 4-year funding supported by the MoE and NSC Excellency project,
the NCU is going to build up the facilities at the Lu-Lin Observatory. This
effort, which is coordinated by the Institute of Astronomy of the National
Central University, will focus on the road construction, water and power
supplies, communication links and other items necessary for the establishment
and maintenance of the Lu-Lin Observatory as an inter-university astronomical
facility for research and education. Members currently involved in this joint
venture are Central University (which is operating the Lu-Lin Observatory),
Tsinghua University and Taiwan University, but we have the vision that many more
universities will be included in this consortium in the near future. We believe
that the proposed national infrastructure will promote Taiwan's role in many
first-class astronomical projects-from solar system astronomy to cosmology--in
view of its capability to provide key longitudinal and time coverage.
work would not have been possible without the effort of a lot of people working
on developing the site. We wish to thank the long term supporting from the
National Science Council of Taiwan, the Ministry of Education of Taiwan and the
National Central University.
A. (1987). "Identification,
Optimization, and Protection of Optical Telescope Sites"
Proc. of an International Conf. Flagstaff, AZ.
W.P., Tsay W.S., Lemme C., Wang J. H., "Taiwan-American Occultation
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W.S. et. al., (1999) “The NCU Lu-Lin Observatory and its Future Direction”,
Proceedings of Fourth East-Asian Meeting on Astronomy, Supplement 1999, p24.
Chen: How many nights around the year could be used for the Photometry? How
about the water vapor in Lu-Lin?
Tsay: Around half of the clear nights could be available for the Photometry.
Unfortunately we do not have the measurement of water vapor during the site
Gaustad: Is the absence of a road due to the cost of construction, or to
regulations of the National Park which forbids it?
Tsay: Both. Construction of a road is estimated to cost US$5 millions. But also,
current policy of the Yu-Shan National Park doesn’t allow the kind of road
needed, which must spiral around the mountain. High level political discussion
Mack: Burying the power line is a good idea environmentally. But do you expect
problems of damage from earthquakes?
Tsay: The power line company will be responsible for maintenance of the
underground power line.