Good morning all,
i’m just working on some flags which should give me the option to reacht on various “time”. example: Night ist between atroDawn und astroDust of the Astro binding. So far so easy, but in the astro binding i found two type where i am not able to translate them to german or understand them in english, because i find no explanation. Maybe someone could help me out.
morgingNight and eveningNight
Thomas
Interesting question. Generally speaking, these should reflect the difference between different definitions of day and night as per here:
But when I look at the code I see an asymmetry which bothers me:
public String toString() {
return new ToStringBuilder(this, ToStringStyle.SHORT_PREFIX_STYLE).append("sunrise", getRise())
.append("noon", getNoon()).append("sunset", getSet()).append("night", night)
.append("morningNight", morningNight).append("astroDawn", astroDawn).append("nauticDawn", nauticDawn)
.append("civilDawn", civilDawn).append("civilDusk", civilDusk).append("nauticDusk", nauticDusk)
.append("astroDusk", astroDusk).append("daylight", getDaylight())
.append("eveningNight", getEveningNight()).append("eclipse", eclipse).toString();
}
Maybe just me, but there’s an asymmetry between the treatment of morningNight and eveningNight that just seems WRONG.
Bob
Now i created a table for my place with all possible values an found some funny/strange things. Firt here is the table:
MorningNight_Start 00:00
MorningNight_Stop 04:00
Night_Stop 05:02
AstroDawn_Start 05:00
AstroDawn_Stop 05:45
NauticDawn_Start 05:45
NauticDawn_Stop 06:27
CivilDawn_Start 06:27
CivilDawn_Stop 07:02
Sunrise_Start 07:02
Sunrise_Stop 07:06
Daylight_Start 07:06
Noon_Start 13:17
Noon_Stop 13:18
Daylight_Stop 19:27
Sunset_Start 19:27
Sunset_Stop 19:31
CivilDusk_Start 19:31
CivilDusk_Stop 20:06
NauticDusk_Start 20:06
NauticDusk_Stop 20:48
AstroDusk_Start 20:48
AstroDusk_Stop 21:33
Night_Start 21:33
EveningNight_Start 21:33
EveningNight_Stop 00:00
Firt thing i reconized is that sunrise and sunset have a duaration of 4 minutes. Next is that the night stops two minutes after AstroDown and that there is a difference of about one hourbetween Moning Night Stop and Astro Dawn Start /Night Stop.
Could someone give a statement on this? Bob remarked the asymmetry as well.
Thomas
This is from that bastion of accuracy, Wikipedia!
As sunrise and sunset are calculated from the leading and trailing edges of the Sun, respectively, and not the center, the duration of a day time is slightly longer than night time (by about 10 minutes, as seen from temperate latitudes). Further, because the light from the Sun is refracted as it passes through the Earth’s atmosphere, the Sun is still visible after it is geometrically below the horizon.
So I guess the four minutes for the sunset and sunrise events might match the transit of the sun disk across the horizon line?
Thanks for that explanation. After reading it is very clear to me. Now only the other questions are open.
Thomas
Noon looks pretty wrong too!
I don’t see a mistake in noon 
Noon is just a moment, so in principle not even a minute long.
And noon on central european summertime should be at about 13:00, because in summertime we are living in the wrong time zone in summer.
As the CET timezone is bigger than intended, noon can occure earlier or sooner than 1300 in summer or 1200 in winter at your destination…
you can calculate when it should occur (derivation is about a second because of the inconsistenticy of the angular speed of the earth, which also causes the differences between UTC, GMT and UT1, which are in principle same, but can differ by about that amount from each other). For easiness and we are just interested in the minute, we can assume noon to happen at 12:00 UTC at the greewich meridian (0°).
The earth rotates 360° in 24h, makes 15° in 1 hour. So in principle if you are living 15° east of Greenwich your noon is 1h before the noon at Greenwich. That is where the next timezone (UTC+1) should start, but it doesn’t because time zones are “political” and there is summertime (or daylight saving time), which in fact shifts your noon by one hour.
I e.g. live at nearly exact 7.5° East… which means, my noon is (7.5°/360°)(24h60min/h) = 30 min before Greenwich noon = 11:30 UTC, 12:30 CET (UTC+1) or 13:30 CEST (UTC+2).
So there is nothing wrong with the time of @Dibbler42 s noon. It just means he has summertime and is living aproximate another 3.75° more east. I’d guess somewhere between 10,9° and 11° east