AstorPearls - Astronomy Software

Welcome to DarkMatters…

DarkMatters is not just a Moon phase displaying program; it is designed mainly to provide you with information about how much darkness you have within the day. This makes it useful for planning stargazing trips, star parties, and even fishing and hunting trips!

How it works?

DarkMatters uses both the Moon rise/set time and the Sun twilight begin/end times to figure out how much darkness you’ll have between the two consecutive twilights – Twilight end of today and Twilight Begin of tomorrow. It allows you to choose between three types of twilights: Civil, Nautical, and Astronomical. DarkMatters also allow you to use you custom twilight by setting the twilight angle you desire.

What information it provides?

With three display views available, you’ll find all information you need about Moon, Sun, and dark time very easily. Each view is explained in details below

One Day View

One Day view

This is the first display view you’ll see when you start DarkMatters. It will show you detailed information about Moon, Sun, Twilight, dark period for this day. Here is a list of information displayed:

  • Dark Period:

    • Length: length of the dark period today.

    • Start: Time of the beginning of the dark period. This time will depend on the moon rise/set and twilight events for this day and the following day. It also depends on your twilight choice.

    • End: time when darkness end.

    • Darkness Bar : This is a bar that represents the length of the dark period. The longer the dark period, the longer the bar will be. This provides a very effective way to evaluate the day (in terms of darkness) in one glance!

  • Moon rise and set information.

  • Sun rise and set information.

  • Twilight information: including the three types of twilight (Civil, Nautical, and Astronomical).

  • Moon phase : this will not only display the phase of the moon, DarkMatters takes into consideration the position angle of the moon. So you’ll see the moon as it appears in the sky in the selected day.

  • Special Day marks : DarkMatters will mark the New Moon’s day with special icons allowing you to recognize these important events in a glance.


When you start DarkMatters it will display today’s information for your current day. You can use the navigation bar at the top to jump to next day, previous day, or go back to today’s information. Information will be updated as you navigate

One Month View

##Month view

This view provides a unique display of the dark time over a month by displaying a bar chart for the darkness over the selected month period. It provides a very convenient way for planning your observing trip . It will also show the moon phase for a selected day and the start of darkness. Bars will have the icons for the New Moon’s day allowing you to recognize this day very quickly.


  • You can navigate to next/previous month or go back to current month using the Navigation bar at the top.

  • Click the blue bar for the day (or the text of the day’s date) to see phase and start of darkness for this day. ___

Ten Days View

Ten days view

With the One Day view you see lots of details for a single day. With the Month view, you see information about darkness over the whole month with fewer details about each day. This view comes in the middle! It provides you with a great balance between amount of details and darkness over 10 days. Navigation and selection can be used in this view as well giving you maximum flexibility.

Settings (some info apply only to desktop version)

DarkMatters allows you to save different settings configurations for different location of interest. You can switch to your favorite location by simply selecting the configuration settings for this location.

  • Location: you can either select your country/state/city from hundreds of built in locations, or select Custom Site (first item in the country list) then set your longitude, latitude, and time zone offset (difference from Greenwich).

  • Time Zone: allows you to select time zone for your region.

  • Dark Period Settings: these settings controls how the dark period is calculated

    • Twilight Used: Which twilight used by DarkMatters to calculate the dark period. You can choose one of the three types of twilights or choose Custom Angle and enter the angle you desire.

    • Moon offset: moon offset is the time added to the moon set time and subtracted from the moon rise time before calculating dark time. This offset allows you to ensure the maximum amount of darkness. Dark periods will be shorter if you choose large offset. Following are values possible:

    • No Offset: DarkMatters will use the moon rise/set times as is.

    • Automatic: DarkMatters will choose a value for you based on the illumination ratio of the moon.

    • Custom Offset: you can choose an offset between 15 – 60 minutes.

  • Display Settings: allow you to choose user interface language and time format (12hr or 24hr).

  • Settings Configurations: here you can add more configurations for other locations of interest. To add a configuration:

    • Click the text area and write a name for the new configuration.

    • Click Add.

    • Customize your settings by choosing location, time zone…etc

    • You are done! Your settings will be saved automatically.

Questions? Email us at and we’ll be happy to answer any question you have.