judhistira judhistira | Indonesia University of Education (original) (raw)
Papers by judhistira judhistira
by A. Warsito, Jehunias Leonidas Tanesib, Jehunias L E O N I D A S Tanesib, C. Kunjaya, M. Yusuf, Hesti Retno Tri Wulandari, E. Akbar, Premana Premadi, anton Jaelani, Andriyan Suksmono, Falahuddin Arief, and judhistira judhistira
Experimental Astronomy, 2014
We report the first measurements of radio frequency spectrum occupancy performed at sites aimed t... more We report the first measurements of radio frequency spectrum occupancy performed at sites aimed to host the future radio astronomy observatory in Indonesia. The survey is intended to obtain the radio frequency interference (RFI) environment in a spectral range from low frequency 10 MHz up to 8 GHz. The measurements Exp Astron (2014) 37:85-108 permit the identification of the spectral occupancy over those selected sites in reference to the allocated radio spectrum in Indonesia. The sites are in close proximity to Australia, the future host of Square Kilometre Array (SKA) at low frequency. Therefore, the survey was deliberately made to approximately adhere the SKA protocol for RFI measurements, but with lower sensitivity. The RFI environment at Bosscha Observatory in Lembang was also measured for comparison. Within the sensitivity limit of the measurement equipment, it is found that a location called Fatumonas in the surrounding of Mount Timau in West Timor has very low level of RFI, with a total spectrum occupancy in this measured frequency range being about 1 %, mostly found at low frequency below 20 MHz. More detailed measurements as well as a strategy for a radio quiet zone must be implemented in the near future.
Based on data record of young lunar crescent (hilal) observations around the world, now we have b... more Based on data record of young lunar crescent (hilal) observations around the world, now we have basic scheme of hilal visibility judgement (i.e. hilal can be observed with naked eye, requiring the help of an optical instrument, or hilal can not be observed at all) according to certain physical parameters chosen. Hitherto a mathematical model that predicts the hilal visibility for a particular location only consider Moon-Sun geometry configuration and twilight sky brightness factors. This paper discusses hilal visibility predictions on telescopic-based visual observations which include the age of the observer, the light transmission in the optical instrument, the size of the mirror/lens as light collector and the magnification of the telescope used as well. The model accommodates all of the above factors are then applied to predict the next hilal visibility for the beginning of Ramadan, Shawwal and Dul-hijjah 1435 Hijri (2014 AD).
Kastner visibility function model for near-Sun objects has been used to make predictions on visib... more Kastner visibility function model for near-Sun objects has been used to make predictions on visibility of hilal of Ramadan and Shawwal 1434 H for a number of locations within the National Hilal Observation Network. Predictions made for the mode of visual observation both using naked eye and telescope-aided observation. Due to weather constraints, the model predictions for the case of the beginning of Ramadan 1434 H (July 8, 2013) did not obtain confirmation from the entire sites. Meanwhile, for the case of Shawwal 1434 H (August 7, 2013) there were confirmations on hilal visibility from several places. We consider only the witness from Makassar that provide authentic evidence of a digital picture of hilal. Based on this, Kastner model proved capable of providing predictions in good agreement with the observational result. Interestingly, prediction of Odeh model, which is the more established one, was in opposite results with prediction of Kastner model.
by A. Warsito, Jehunias Leonidas Tanesib, Jehunias L E O N I D A S Tanesib, C. Kunjaya, M. Yusuf, Hesti Retno Tri Wulandari, E. Akbar, Premana Premadi, anton Jaelani, Andriyan Suksmono, Falahuddin Arief, and judhistira judhistira
Experimental Astronomy, 2014
We report the first measurements of radio frequency spectrum occupancy performed at sites aimed t... more We report the first measurements of radio frequency spectrum occupancy performed at sites aimed to host the future radio astronomy observatory in Indonesia. The survey is intended to obtain the radio frequency interference (RFI) environment in a spectral range from low frequency 10 MHz up to 8 GHz. The measurements Exp Astron (2014) 37:85-108 permit the identification of the spectral occupancy over those selected sites in reference to the allocated radio spectrum in Indonesia. The sites are in close proximity to Australia, the future host of Square Kilometre Array (SKA) at low frequency. Therefore, the survey was deliberately made to approximately adhere the SKA protocol for RFI measurements, but with lower sensitivity. The RFI environment at Bosscha Observatory in Lembang was also measured for comparison. Within the sensitivity limit of the measurement equipment, it is found that a location called Fatumonas in the surrounding of Mount Timau in West Timor has very low level of RFI, with a total spectrum occupancy in this measured frequency range being about 1 %, mostly found at low frequency below 20 MHz. More detailed measurements as well as a strategy for a radio quiet zone must be implemented in the near future.
Based on data record of young lunar crescent (hilal) observations around the world, now we have b... more Based on data record of young lunar crescent (hilal) observations around the world, now we have basic scheme of hilal visibility judgement (i.e. hilal can be observed with naked eye, requiring the help of an optical instrument, or hilal can not be observed at all) according to certain physical parameters chosen. Hitherto a mathematical model that predicts the hilal visibility for a particular location only consider Moon-Sun geometry configuration and twilight sky brightness factors. This paper discusses hilal visibility predictions on telescopic-based visual observations which include the age of the observer, the light transmission in the optical instrument, the size of the mirror/lens as light collector and the magnification of the telescope used as well. The model accommodates all of the above factors are then applied to predict the next hilal visibility for the beginning of Ramadan, Shawwal and Dul-hijjah 1435 Hijri (2014 AD).
Kastner visibility function model for near-Sun objects has been used to make predictions on visib... more Kastner visibility function model for near-Sun objects has been used to make predictions on visibility of hilal of Ramadan and Shawwal 1434 H for a number of locations within the National Hilal Observation Network. Predictions made for the mode of visual observation both using naked eye and telescope-aided observation. Due to weather constraints, the model predictions for the case of the beginning of Ramadan 1434 H (July 8, 2013) did not obtain confirmation from the entire sites. Meanwhile, for the case of Shawwal 1434 H (August 7, 2013) there were confirmations on hilal visibility from several places. We consider only the witness from Makassar that provide authentic evidence of a digital picture of hilal. Based on this, Kastner model proved capable of providing predictions in good agreement with the observational result. Interestingly, prediction of Odeh model, which is the more established one, was in opposite results with prediction of Kastner model.