URCUN is an HTML/JS application which can be accessed by the WEB browser of any device to obtain the Moon Crescent Visibility Map of any lunation between 1901 and 2099 (JavaScript must be enabled). The desired date may be selected as Gregorian or Hijri, such that the application can also be used as Gregorian / Hijri calendar converter. URCUN computes the visibility according to the Extended Crescent Visibility Criterion. Detailed explanation about the Analytic Derivation & Topographic Application of the Crescent Visibility Parabola Function can be found here.


If the solar calendar is to be used, then the Gregorian Date field on the form should be selected. You can change the date over a pop-up calendar or by up-down buttons (depending on your browser) on this field. The associated Hijri Date is automatically displayed on the next field. If the lunar calendar is to be set instead, then enter the Hijri date into the Hijri Date field. The Hijri day must be a value between 1 and 30, and the year between 1319 and 1523. The Hijri month should be selected from the drop-down menu. If the selected month has only 29 days and you entered 30 into the day field, the application automatically decreases the day to 29. You can see the associated Gregorian Date after entering the Hijri Date. When the form is loaded the first time, the current date will be shown in both date fields. The common need for a visibility map is to determine the onset of a new lunar month, so the application shows the first visibility of a new (waxing) crescent as default. However, you may also need to analyse the last visibility of an old (waning) crescent. For this case, select the "Waning" option from the Crescent drop-down menu.


The Extended Crescent Visibility Criterion regards the altitude (a.s.l.) as a parameter, so you may as well adjust the altitude on the form, by entering a value between 0 and 4,000 into the Altitude field. If you check the Auto box, the application calculates the visibility using the altitude information of each location automatically and displays the topographic visibility map, where the zones are no more smooth parabolas. In this "Auto" mode, the Altitude value is disregarded and it cannot be entered manually.


Every time a parameter is changed, the application redraws the visibility map. If you move the pointer over the map, the coordinates of the pointed location, together with the altitude, will be shown. Just click on the map if you want to extend it to see the next day (or the previous day for the case of the waning crescent). You will return back by clicking again.


The time and location of the first/last visibility for each zone is printed below the map. The violet line on the map represents the Best Visibility Line.

The zones are defined as following:

  • Zone-A: Easily visible even by naked-eye
  • Zone-B: Usually visible by naked-eye; easily visible by optical aid
  • Zone-C: Rarely visible by naked-eye; usually visible by optical aid
  • Zone-D: Not visible by naked-eye; rarely visible by optical aid
  • Zone-E: Not visible even by optical aid


Furthermore, the application can sketch a regional map according to the Isha-based Regional Moonsighting concept, which relies on the ittihad-ul-matali principle. To obtain this map, select the "Regional" option from the Crescent drop-down menu.


In this case, the zone colors will be defined as:

  • Crescent globally visible before local isha
  • Crescent globally visible before 1/3 of local night
  • Crescent globally visible before 1/2 of local night
  • Crescent globally visible before local fajr
  • Crescent globally visible AFTER local fajr


Click to go to the URCUN application