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Deep Sky Darkness calculator

 
To open the Deep Sky Darkness calculator double click on Darkness Clock
located in the Status panel of the Main Screen or with Alt+D shortcut.
 
The Deep Sky Darkness (DSD) calculator gives possibility to see details for different events in the current or selected night. Maybe the most important feature of imaging night is time of complete darkness that can be used for collecting data for deep sky objects. This calculator is mainly focused on this and calls it - Deep Sky Darkness Time (DSD Time). To have DSD the Moon has to be below the horizon and the astronomical twilight should be already ended or not started yet. The calculator also allows searching for a night with desired DSD Time.
 
Take a look on the free (yes, free - no ads or marketing) Androind and iOS versions of the Deep Sky Darkness Calculator - Darkness Clock
 
Deep Sky Darkness calculator
 
1

Night dates

1.  Night dates
 
The dates of the night that is currently displayed. It can be the current or selected night.
 
2

Night Bar

2.  Night Bar
 
The night bar shows the events in the selected night and the Moon phase. Used is the same events coding as in Darkness Clock.
 
3

Evening - Morning

3.  Evening - Morning
 
In the left column are the selected evening events - time of the sunset, the end of the nautical twilight and the end of the astronomical twilight which is the actual start of the night.
In the right column are the selected morning events - the start of the astronomical twilight which is the actual end of the night, the start of the nautical twilight and the time of sunrise.
 
4

The Moon

4.  The Moon
 
Here are the Moon events.
 
  • The first line shows the moon rising and setting times in the selected night.
  • Illu Range - shows the illumination percent in Moon rise and set moments in the selected night.
  • Age Range - shows the age in Moon rise and set moments in the selected night.
  • Current Illu - shows the illumination percent in the current moment (uses the computer clock)
  • Current Age - shows the age in the current moment (uses the computer clock)
 
 
5

Darkness

5.  Darkness
 
Shows when the when starts/ends the time suitable for imaging of deep sky objects - Deep Sky Darkness (DSD) in the selected night. DSD = No Moon and twilight.
 
6

The total dark time

6.  The total dark time
 
Shows how long Deep Sky Darkness (DSD) will be in the selected night. DSD = No Moon and twilight.
 
7

Change Night

7. Change Night
 
Allows to change the night which events are loaded. The Prev/Next buttons change the date with one day. You can also enter particular date  and press the Enter key to recalculate.
 
If you press the Enter key on empty edit box, APT will use the current date.
 
8

Find Night

8. Find Night
 
You can search for the closest night which has Deep Sky Darkness (DSD) Time equal or more to the entered one. The value is in hours and accepts decimal numbers like 6.5