We propose a new Hilaal (lunar crescent formed immediately after conjunction) visibility criterion apply to tropical region utilizing modified mathematical model of near-sun objects visibility. By using only naked eye positive sightings of Hilaal, then we are calculating the Moon and Sun observation parameters to obtain the visibility function for each case. Moon – Sun altitude difference (ARCV – Arc of Vision) and elongation (ARCL – Arc of Light) at the first observable moment have been chosen as parameters and used in developing new visibility criterion. The data show that the minimum ARCV and ARCL value for naked eye observation at the moment of Hilaal is observed are 8.4° and 7.1°, respectively. Our results can be proposed as a scientifically criterion for constructing Hijri calendar for tropical region (including Indonesia) as an alternative to Jakarta Recommendations criterion.

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Meteorological parameters such as wind speed, air temperature and pressure have been measured in the Menara Timur, FPMIPA UPI, Bandung, Indonesia during the Tropical Cyclone Cempaka Dahlia (TCCD) from November 27 until December 2, 2017. In this paper, we propose to analyze them by using distance measurement for time series data. The following steps are conducted: data collecting, splitting, dimensionality reducing, and distance calculation. The final results show cluster memberships of the three parameters on 3 time frames: one week before, the TCCD week, and one week after. After doing some simulations, it can be seen that profiles of temperature and pressure at the time frame before and during are similar. However, for wind speed we can see that the profile of the time frame before and after is quite similar compared with the others. In conclusion, the wind speed parameter is strongly affected by TCCP with an increase in the wind speed up to 74% compared by wind speed before TCCP

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