Developing Telescope Baffle for Increasing Contrast of the Very Young Lunar Crescent Visibility (original) (raw)

ANALYSIS OF OBSERVATIONS OF EARLIEST VISIBILITY OF THE LUNAR CRESCENT

The Observatory, 2018

Predicting the visibility of thin lunar-crescents following the new moon is difficult and challenging for several technical reasons. The visibility of the earliest new moon has long been used to determine the lunar-crescent calendar and is still used today. Many criteria exist for the first visibility of the lunar crescent. Here, we test the most-commonly-used criteria for thin-lunar-crescent visibility.We used 545 observations, including both positive and negative sightings, made by professional and highly-trained astronomers over duration of 27 years 1988 2015) and from different locations at latitudes between 20° N and 29° N (within Saudi Arabia). We developed new criterion for lunar-crescent visibility using lunar-crescent width W ) and the arc of vision (ARCV).This new model can be used to predict the visibility of the lunar crescent by naked eye or aided eye, which is fundamental for the lunar-crescent calendar followed by several cultures and religions.

Application of Scientific Approach to Determine Lunar Crescent’s Visibility

Middle-East Journal of Scientific Research, 2012

Abstract: The visibility of lunar crescent has been explained in Islamic Law (fiqh) by previous scholars. Until today, the explanations which were nuance in qualitative sense are still provide vacuum and need to be studied critically with different method particularly in quantitative approach. Therefore, this paper will present the application of scientific approach using sky illumination measurement to explain lunar crescent's visibility. The approach combines computational and observational technique will help fiqh in ...

Predicting the First Visibility of the Lunar Crescent

Academia Letters, 2021

We observe the first visibility of the lunar crescent on the western horizon shortly after sunset, and it is the beginning of the month in the Islamic calendar. There are numerous techniques for predicting the day of the first sight of the Moon, but our interest is in the physical method, which began with the investigations of Samaha, Assad, and Mikhail (1969) and Bruin (1977). To predict when we will observe the first crescent Moon, we need: 1. The topocentric altitude of the Moon; azimuth difference between the centers of the Sun and the Moon (DZ); Sun depression (d); Earth-Moon distance and topocentric phase angle (or selenocentric angle between the observer's position and the center of the Sun). 2. The luminance of the Moon without atmospheric absorption for the phase angle; (we understand luminance as the luminous flux per unit of the luminous area perpendicular to the observation direction and per unit of solid angle). 3. The atmospheric extinction coefficient for the place of observation, which determines the luminance of the Moon Bm at the surface of the Earth. 4. The twilight sky luminance Bs, as a function of d and DZ. 5. The threshold contrast or the threshold illuminance for viewing the Moon in the twilight sky; (we define the contrast by C = Bm/Bs, and the illuminance is the luminous flux that reaches the observer per unit area normal to the observation direction). Photometric measurements of the Moon at large phase angle are difficult since its observation has to be made at a low altitude above the horizon and therefore, is highly affected by atmospheric attenuation; also, the observation has to be done with twilight light, therefore the Moon's own illumination is added to the illumination of the sky, and finally, it must be added

Developing Information System on Lunar Crescent Observations

ITB Journal of Sciences, 2010

We present a progress report on the development of information system of lunar crescent astronomical observations which will be largely accessible for public domain. This consists of calculations of the Moon's ephemeris as well as systematic real-time lunar crescent observations. A well suited small telescope, equipped with a simple digital detector, is connected to a server to provide information on lunar crescent observations. The system has been used and worked well. The only constraint is poor weather condition. Network of small telescopes, installed at various locations in Indonesia, are currently planned to provide plethora of data. In the long term, this will be used to help to determine the astronomical visibility criteria of lunar crescent for Islamic calendar.

Visibility Window of the First Lunar Crescent

We define the width of the window of visibility of the first lunar crescent as the interval of altitudes of the Moon between which we can see the crescent. We define the duration of the visibility window or time during which we see the crescent; and we also define the altitude of optimal vision of the crescent. We check the parameters on which the visibility window depends. We determine the variation of the visibility window with the phase angle, the atmospheric attenuation constant, the latitude of the observation site, and the declinations of the Sun and the Moon.

Bīrūnī's Telescopic-Shape Instrument for Observing the Lunar Crescent

Suhayl, 14, pp. 167–188, 2015

This paper deals with an optical aid named barbakh that Abū al-Ray¬ān al-Bīrūnī (973-1048 AD) proposes for facilitating the observation of the lunar crescent in his al-Qānūn al-Mas'ūdī VIII.14. The device consists of a long tube mounted on a shaft erected at the centre of the Indian circle, and can rotate around itself and also move in the vertical plane. The main function of this sighting tube is to provide an observer with a darkened environment in order to strengthen his eyesight and give him more focus for finding the narrow crescent near the western horizon about the beginning of a lunar month. We first briefly review the history of altitude-azimuthal observational instruments, and then present a translation of Bīrūnī's account, visualize the instrument in question by a 3D virtual reconstruction, and comment upon its structure and applicability.

Computational Astronomy and the Earliest Visibility of Lunar Crescent

Citeseer

Basic techniques of Computational Astronomy are reviewed and presented as the essential tools for simulation of Lunar phenomena. The importance of accurate determination of Julian Date and the Local Sidereal Time is discussed that are essential to determine the local time of sunset and the local coordinates of any object at that time. During the 20 th century, a number of authors have contributed towards the understanding of the problem of earliest sighting of crescent Moon. The work of Maunder, Schoch, Bruin and Schaefer has been crucial in the development of this understanding. More recently, the work of Yallop, Ilyas, Ahmed and Shaukat has received great recognition. The work of Ahmed and Shaukat has been based mostly on the Yallop's Criterion. However almost all the modesl are based on the observational data of Schmidt who made observations from Athens for over 20 years during the late 19 th century. In this work, a model of q-values developed by Yallop is analyzed in view of Maunders and the Indian Criteria along with the actual semi-diameter of the crescent Moon. The basic criterion is modified on the basis of data more recently collected.

The Extended Crescent Visibility Criterion

2017

Crescent visibility has been a concern for determining the start of any lunar month. Various criteria have been offered by the astronomers since the Babylonians. The indigenous criterion proposed in this paper uses the two reliable parameters, altitude and crescent width, and makes it possible to estimate the visibility for any phase of the Moon, not just limited to thin crescents. Though very simple, the algorithm presented here produces rather consistent results. Various visibility graphs are included. In addition is introduced a tool for demonstration.

YOUNG LUNAR CRESCENT VISIBILITY PREDICTION ON TELESCOPIC–BASED VISUAL OBSERVATION

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).

Islamic Historical Review on Middle Age Lunar Crescent Visibility Criterion

Journal of Al-Tamaddun

Middle Age lunar crescent visibility criterion is criterion that was produced during 8th until 17th century. This includes al-Khawarizmi lunar crescent visibility criterion in 8th century until al-Lathiqi lunar crescent visibility criterion in 17th century. Numbers of review on mathematics and astronomy during the Middle Age, however the number of review that specifically written for Middle Age lunar crescent visibility criterion limited, with majority of review is written to study the historical of Middle Age science, astronomy, mathematics and geography as a whole, and not converge on lunar crescent visibility criterion. . Therefore, this article aimed to provide a review on Middle Age lunar crescent visibility criterion. The review is conducted using literature analysis, snowball literature search and specific inclusion and exclusion criteria. The review is performed based on 13 works on lunar crescent visibility criterion that pass the selection criteria. The review found out th...