# Research Topics

## Double Star

Double star research has been carried out since the beginning of the Bosscha Observatory was established. The Zeiss double refractor telescope is specifically designed for this purpose.

## Exoplanet

Exoplanet means a planet orbiting another star besides our Sun. Since 1995 until now, around 3900 confirmed planets have been found orbiting other stars.

## Variabel Stars Study

A variable star is a star which its brightness changes periodically. Some of the causes of this light variability include star’s companion (double/binary or even more) which periodically cover each other (like an eclipse), either partial or fully covered; another cause is the star regularly changes its size (also called a pulsating star).

## Occultation

Occultation is the event of a celestial object being covered by another celestial object, where the angular size of the obscured object is smaller than the object who cover them (for example, the star is covered by the Moon). Astronomers could do study about binarity (or even multiplicity) of the stars i.e to know whether a star has a companion(s) or not. Astronomers also could measure angular diameter of the star, with a very high resolution (order of milliarcseconds or mas ) with a modest telescopes (diameter $\phi <$ 1 m).

## Photographic Plate Digitization

Bosscha Observatory is the oldest Astronomical research institute in Indonesia which is still operating today. In the early days of its existence, Astronomy research was carried out using visual methods and taking pictures with photographic plates. As technology develops, the use of digital sensors replaces the photographic plates so that Bosscha Observatory has a lot of photographic plates that are still intact and are feared to be damaged. This work is aimed primarily at digitizing existing photographic plates, in addition, we are trying to do better archiving of this legacy, as well as conducting research using authentic data from the early era of Bosscha Observatory.

## Crescent Moon Observation System Development

Indonesia is a country with majority of its citizen has Islam as their religion/faith. Bosscha Observatory has been involved in observing young crescent that marks the beginning of the Hijri month, especially Ramadan, Shawwal, and Dhu al-Hijjah since 2007. The youngest crescent that can be observed after sunset is known as Hilal in Bahasa Indonesia. The observation techniques which we used continue to evolve, following technology advancement and our technical understanding of the hilal observation itself. The detectors being used are also varied: from simple webcam, DSLR camera, CCD camera, to CMOS camera. The use of filters also changed: from without using one, the use of ND filters 0.3 + 0.6, and the use of (near)-infrared filters.