Knowing the earth rotation and revolution correctly makes it possible to calculate the time and angle of sunset precisely for any location on Earth as we did with sunrise. We should be aware that there are areas near the poles where the sun remains visible or invisible the whole day. We can calculate sunset from… Continue reading Sunset Calculation

## Sun Rise Calculations

Knowing the earth rotation and revolution correctly makes it possible to calculate the time and angle of sunrise precisely for any location on Earth. We should be aware that there are areas near the poles where the sun remains visible or invisible the whole day. We can calculate sunrise from longitude and equation of time.… Continue reading Sun Rise Calculations

## Sun Distance

Sun distance from earth ranges from 147 million kms to 152 Million kms. Sun distance depends on the time of the year and it is less in winter and more in Summer. The following web app gives this value for any day during the year: Year Sun Distance Today : – Created with Apache Echarts… Continue reading Sun Distance

## Equation of Time

Equation of time is the difference between apparent solar time and mean solar time. EOT = apparent solar time – mean solar time Wikipedia defines EOT by the follwoing: The equation of time describes the discrepancy between two kinds of solar time. The word equation is used in the medieval sense of “reconcile a difference”.… Continue reading Equation of Time

## Sun Right Ascension

Wikipedia defines Right ascension (RA) as the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the (hour circle of the) point in question above the earth. When paired with declination, these astronomical coordinates specify the location of a point on the celestial sphere… Continue reading Sun Right Ascension

## Proportion Test – Example

In the previous post, we explained how to calculate P-value and thus perform hypothesis testing for categorical data. In this post we will give an example. A study was performed to see if there is a difference between males and females who use cannabis regularly. The sample size was 134 , 51 Females and 83… Continue reading Proportion Test – Example

## Proportion Test

The parameter of interest when we deal with categorical data is the sample proportion. An example of a sample proportion could be the proportion of people that are use cannabis. Imagine that we want to compare the proportion of males that are cannabis users to the proportion of females that cannabis users. Our two groups… Continue reading Proportion Test

## Null Hypothesis

Null hypothesis is effectively stating the default situation. It is as you said there is nothing going on. When some one puts forward a claim the null hypothesis is that this claim is not true and needs to be proven. When we are testing between a new claim and the null hypothesis, a null hypothesis… Continue reading Null Hypothesis

## Islamic Prayer Times

Moslems Must Observe the apparent movement of the sun across the sky in order to performs prayers. There is no consensus on the times of the prayers among different Moslem factions and developing an algorithm was affected by this fact. For example, Sun depression angle considered to calculate Fajr and Isha prayers are not agreed… Continue reading Islamic Prayer Times

## Directions On Map

The direction between any two places on Earth can be calculated using the spherical trigonometry. We can use the following equation to do that Direction Angle =tan-1 (sin(longitude2 – longitude1)/cos(latitude1)*tan(latitude2)-sin(latitude1)*cos(longitude2-longitude1)) In spherical trigonometry values of latitude and longitude represent angles as in the following diagram: Example One famous example is The Islamic Qibla. Muslims need… Continue reading Directions On Map