# Research Instruments

## Zeiss Double Refractor Telescope

Telescope name Zeiss
Diameter 0.6 m (double)
Focal length 1080 cm (or 10.8 m)
Focal ratio f/18
Plate scale 18.4”/mm

The 0.6 m Zeiss Double Refractor Telescope, or Zeiss Telescope for short, is located in the only dome-shape building at Bosscha Observatory which has been a landmark of Northern Bandung for more than 85 years. This telescope building was designed by renowned Bandung architect, K.C.P. Wolf Schoemacher, who is also teacher of first Indonesian president, Soekarno. This telescope and its building was donated by K.A.R. Bosscha and then officially handed over this observatory to the Dutch East Indies Astronomy Association in June 1928. The dome weights 56 tons with a diameter of 14.5 m and is made of 2 mm thick steel. Today, Zeiss Telescope is the largest and the oldest telescope at Bosscha Observatory.

So far, this telescope is still working properly thanks to our technicians who do a consistent maintenance. Photographic detector systems were used in this telescope until 1980s. Since the early 1990s, digital detector technology (using astronomical CCDs) began to be used at Bosscha Observatory to improve detector sensitivity. In addition, telescope instrumentation also continues to be modernized. This telescope is a refractor (it is using a lenses) and it consists of 2 main telescopes and 1 finderscope. The diameter of the main telescope is 0.6 m with a focal length of almost 11 m. Finderscope has a smaller diameter of 0.4 m. The field of view of the finderscope is 1.5 degrees or about 3 times the diameter of the full Moon. This wide field of view makes it easy to identify the target star to avoid mis-detection by comparing it with sky map or sky chart of this particular sky region. This telescope can observe stars 100000 times dimmer than stars that can be seen by the naked eye. This telescope has been used for a variety of astronomical studies, including for astrometric observations to obtain information on the position of celestial bodies accurately in the order of a tenth of a arcseconds, to construct a visual double-star orbit. Up until now, there are about 10000 visual double-star observation data obtained using this telescope. In addition, this telescope is also being used for observing the proper-motion of stars in star clusters. This telescope is used for measurements of stellar parallax to determine the distance of stars. CCD imaging is also used for observing comets and planets, e.g. Mars, Jupiter and Saturn. We also did a spectroscopic study of Be Star by attaching BCS (Bosscha Compact Spectrograph) onto this telescope.

## Bosscha Robotic Telescope (BRT)

Telescope type Corrected Dall – Kirkham
Optical Tube Assembly Planewave CDK 14
Diameter 14 inch (0.36 m)
Focal length 2592 mm
Focal ratio f/7.2
Detector CCD FLI PL 11002

This is one of new telescopes in Bosscha Observatory. This telescope could produce distortion-free area around 70 mm thanks to its design (i.e. Corrected Dall-Kirkham). With carbon-fiber truss, this telescope is relatively lightweight (less than 30 kg). This telescope system also equipped with automatic focus system and temperature regulation system to avoid dew in its main mirror. Accompanied by pro-class Astrophysics 1600 GTO mounting, we could point to and track celestial bodies with high accuracy.

We mostly use this telescope for exoplanet study, and occassionally is being use for detecting NEA (Near Earth Asteroid). We also use this telescope to observe variable stars. We manage to make this telescope robotic i.e. programmable to minimize human interaction and could adapt to sky condition. We also could operate this telescope remotely by using internet network.

## STEVia Telescope

Par. Main Telescope Guider Scope
Telescope type Schmidt – Cassegrain Reflector Refractor
Diameter 279 mm (0.279 m) 66 mm
Focal length 1760 mm 388 mm
Focal ratio f/6.3 f/5.8
Detector CCD SBIG ST – 8 XME CMOS ZWO ASI 120MM
Filter BVRI (narrow band) and LRGB (broad band) -
Field of View 26.8 $\times$ 17.9 arcmin 43 $\times$ 32.3 arcmin

STEVia telescope (Survey Telescope for Exoplanet and Variable star) is telescope system at Bosscha Observatory which was assembled in 2013. The building where STEVia reside is a historic building, once occupied by legendary Unitron telescope. This telescope system is computerized and could be operated remotely by using internet network.

STEVia is equipped with guider scope to ensure stable tracking of celestial bodies, especially when take data/image with long exposure time.

Main purpose of this telescope is star cluster survey to find new exoplanet and variable stars. This telescope also being use for impromptu observation e.g. supernova and occultation phenomena.

## GAO-ITB RTS (Remote Telescope System)

Telescope type Schmidt - Cassegrain reflector
Diameter 279 mm (0.279 m)
Focal length 2790 mm
Detector SBIG ST - 8 XME
Spectrograph NEO - R1000

GAO-ITB RTS (RTS = Remote Telescope System) is established in 2005, and is one of remotely-capable and computerize telescope at Bosscha Observatory. This telescope is a result of joint-research collaboration between ITB and GAO (Gunma Astronomical Observatory) Japan. In several occassion, this telescope is remotely-controlled by our colleagues in Japan to observe star lies on Southern Hemisphere, mostly for educational purposes.

From 2015, the main scope was renewed with a slightly larger aperture (0.28 m in diameter) and switch the mounting, from takahashi Temma EM200 to Losmandy G11. This telesope also equipped with a new spectrograph as collaboration between ITB and Kyoto Sangyo University, Japan which intended to use as spectroscopic study of emision line of extended object such as comet, supernovae, and planetary nebulae.

## Surya Telescope

The Surya Telescope or Solar Telescope is a digital telescope system which consists of 3 Coronado telekop with 3 different filters, equipped with a fully self-made Sun image projection telescope. This facility could be established thanks to donations from the Ministry of Education, Science, and Culture, the Netherlands; Leids Kerkhoven-Bosscha Fonds; and the Ministry of National Education, and the State Ministry of Research and Technology. This new facility can be used for research, education, and for community service. In terms of public services, this facility will be an important part of informal education that can be provided by the Bosscha Observatory to the public. All of this is a form of the Bosscha Observatory efforts to modernize itself while still maintaining its history. This solar telescope facility stands on land of a former transit telescope that is no longer in use, and was once used as a topographic observation point. This building was designed by Dr. Wijaya Martokusumo from SAPPK-ITB.

This facility consists of two telescope systems, the first of which is a digital telescope working at 3 wavelengths: H-$\alpha$, Calcium II, and white light aimed at observing sunspots. The second telescope is a coleostat aimed at making analog projections and solar spectra. Thus both can function as real-time telescopes, and can be seen through the internet network. With this system, this facility can collect scientific data as well as public education. Variations in the appearance of the sun can be monitored and the public is expected to perceive the phenomenon of space weather.

The Solar telescope facility is also equipped with posters containing information about the Sun and World Wide Telescope software that was donated by Microsoft Indonesia to the Bosscha Observatory.

## Portable Telescope

This telescopes are intended to use as mobile system. They have various diameters range from 66 mm to 0.2 m. Students usually use this telescope for their laboratory works, internship, or for public services. They are two monopod that could be use with the telescope as semi-permanent system.

## Bamberg Telescope

Diameter 37 cm
Focal length 700 cm
Focal ratio f/18.9
Filter Solar filter

The Bamberg Telescope is one of refractor telescopes at the Bosscha Observatory, with the diameter of 0.37 m and a focal length of 7 m. This telescope is reside in a half-cylinder roofed building with a sliding roof. Because of the shape of the building, the telescope is only limited to observing celestial bodies with a zenith distance of 60$^\circ$, or for celestial objects higher than 30$^\circ$ and azimuth in the East-South-West sector. For celestial objects in the northern sky or the azimuth East-North-West sector is practically inaccessible by this telescope. This telescope was installed early in 1929 and its tracking system is feed by a gravity pendulum system which automatically regulates the speed of the telescope moving westward following the stars in the field of view of the telescope in accordance with the speed of rotation of the earth. This telescope has also been equipped with a modern detector in the form of a CCD camera.

The Bamberg Telescope is used for observing the light curves of variable stars, as well as photometric eclipses of stars. This telescope is also used for observing the Sun and the surface of the Moon. The Bamberg Telescope is also often used for public education, for example on Public Nights. Visitors are usually fond to see Moon’s craters, visual double stars, star clusters, planets and other celestial bodies directly through the eyepiece or ocular.

## GOTO Telescope

Diameter 45 cm
Focal length 540 cm
Focal ratio f/12
Plate scale 38.2”/mm
Status under maintenance

GOTO telescope is using mirror as a collector of light. We call this design a reflector telescope. This telescope has Cassegrain design with a mirror diameter of 45 cm. The main mirror which has a parabolic shape has a focal length of 1.8 m and the secondary mirror that has a hyperbole shape has a focal length of 5.4 m. This telescope was aided by the Japanese Ministry of Foreign Affairs through the ODA (Overseas Development Agency) program, Ministry of Foreign Affairs, back in 1989. This telescope was the first telescope at Bosscha Observatory which was fully driven by computer control and was equipped with CCD cameras and other instruments. This telescope control system was damaged due to lightning and now been completely replaced with a control system that is compatible with ordinary PCs.

This telescope is used mainly for observing variable stars, exoplanet, observing asteroids, star spectroscopy, and planetary imaging.

## Schmidt Bimasakti Telescope

Diameter 71 cm
Focal length 127 cm
Focal ratio f/1.8
Status under maintenance

The Schmidt Telescope was installed in 1960 and was a donation from UNESCO to the Bosscha Observatory. This type of telescope is rare in the world. The Schmidt Bimasakti Telescope has a Schmidt optical system so it is often called the Schmidt Camera. This telescope has 51 cm corrector lens, 71 cm of main mirror, and 127 cm focal length. This telescope also has the smallest relative f-ratio among the large telescopes at Bosscha Observatory whic is f/2.5, so it is similar to an ordinary camera f-ratio. Therefore, this telescope is even called fast system, while the Zeiss Double Refractor is a slow system. it means that it takes longer exposure take an image of the same object when using a Zeiss refractor compared with Schmidt telescope.

This telescope has a wide field of view, approximately $5 \times 5$ square degrees, so this telescope are very good for survey purposes. We used this telescope for observing celestial objects from blue wavelengths to near infrared, equipped with objective prisms and Racine prisms. Because of its fast-nature system, this telescope is very sensitive could easily disturbed by light pollution. In the past, this telescope is used for observing hydrogen emission line stars, class M stars, and Wolf-Rayet stars.

## Hidrogen Radio Telescope 6 m

Status: under maintenance

This telescope is called Teleskop Radio Hidrogen which has a diameter of 6 m. We use this telescope mainly for observing neutral hidrogen emission on frequency of 1420.4 MHz (it corrresponds to wavelength of 21 cm). This telescope will be developed into interferometry system and that will be the first of its kind in Bosscha Observatory.

There are several tests conducted by both students and researcher from ITB for more that 6 months. Data acquisition of galactic plane continuum to obtain Brightness Temperature ($T_\mathrm{b}$) as function of Right Ascension (RA) drift was done as part of students’ final project. Please see work by Mumtahana (2012) for further details.

Status: under maintenance

The 2.3 m Bosscha radio telescope is an SRT (Small Radio Telescope) type of radio instrument designed by the MIT-Haystack Observatory and made by Cassi Corporation. This telescope works at a wavelength of 21 cm or in the frequency range of 1400-1440 MHz. Within that frequency range there is a neutral hydrogen line transition, so this telescope is very suitable for neutral hydrogen observations, for example in our galaxy, the Milky Way. In addition, this telescope can be used to observe distant objects such as extragalaxies and quasars. The Sun is also an interesting object to study in this radio wavelength. Exotic objects, such as pulsars, will also be the target of observation with this radio telescope.

This telescope can be used for observation in spectral mode with a resolution of 7.8 kHz for 1.2 MHz bandwidth, or with a very high resolution of 1.8 kHz but with much shorter bandwidth. Mapping can also be done, but with a beam resolution of only about 7 degrees. Observation in continuum mode gives a bandwidth as wide as 40 MHz with a bin of 1 MHz. This telescope is installed at the top of the former meteorological tower at Bosscha Observatory to get maximum sky coverage (without being blocked by trees). A control room is located below it. This telescope got its first light in December 2008 and is initiated the development of radio astronomy in Indonesia and will continue to be developed into a multi-element radio interferometer.

Length $\sim$ 7 m