Article
Rising sign with longitude
The simple hour model gets geographic longitude added. It is still a paper sketch, without latitude, a time zone, or an ephemeris.
The Rising sign with longitude calculator does this. It is entertainment and a tradition lesson, not a reading and not life advice.
The idea in brief
The simple hour model gets geographic longitude added. It is still a paper sketch, without latitude, a time zone, or an ephemeris.
You want a rising sign with a place. This card adds longitude to the hour model: hours plus longitude/15, then floor(/2). Latitude and time zone do not enter.
Longitude is not the horizon
A full rising sign needs latitude, a time zone, and an ephemeris. Popular “city calculators” pretend that Warsaw or New York alone closes the case.
Here the hourly model gets longitude: hours plus longitude/15, then floor(/2). 15:00 at 21°E is about 16.4 and a different shift than 15:00 alone. Latitude still stays out. This is a clock correction, not a rise on the horizon.
Words on this page
The short forms below belong to this card only. Another page with a similar name may compute a different rule.
- longitude
- East degrees, range -180 to 180. Warsaw is about 21, New York about -74.
- effectiveHours
- Hour plus longitude/15, then floor(/2). No latitude and no time zone.
- 21°E at 15:00
- About 16.4, so a different shift than 15:00 alone.
What 21 degrees add
Longitude shifts the clock by one hour per 15°. That is a longitude correction, not a rise on the horizon.
A full rising sign needs latitude, a time zone, and an ephemeris. Popular "city calculators" often pretend a name closes the case. Here you can see what is missing.
When this helps
| Situation | What the card shows |
|---|---|
| How is this different from the plain rising sign? | There, shift = floor(hour/2). Here you first add longitude/15 to the hours. |
| How do I type Warsaw or New York? | Warsaw about 21, New York about -74, range -180 to 180. That is longitude, not a city name. |
| Does latitude count? | No. There is no horizon and no houses. |
How to read it
The simpler rising sign uses shift = floor(hours/2). Here we add longitude/15 to the clock first, then take floor(/2).
In east degrees: Warsaw ≈ 21, London ≈ 0, New York ≈ -74, Tokyo ≈ 139. Range -180...180.
Example from the card
15:00 at 21°E
15 + 21/15 = 16.4. floor(16.4/2) = 8. Without longitude floor(15/2) = 7. One extra shift step. 15 May at 8:00 at 21°E is still a sketch, not Warsaw's horizon.
Typical numbers from the card
| Question from the card | This card's answer |
|---|---|
| How does this differ from plain rising sign? | The simpler rising sign uses shift = floor(hours/2). Here we add longitude/15 to the clock first, then take floor(/2). |
| How should I enter longitude? | In east degrees: Warsaw ≈ 21, London ≈ 0, New York ≈ -74, Tokyo ≈ 139. Range -180...180. |
| Does latitude count? | Not in this model. We do not build a horizon or houses. It is only a longitude nudge to the “clock”. |
Typical mistakes
| Mistake | What goes wrong | How to avoid it |
|---|---|---|
| You type "Warsaw" as text. | The field is a degree number. | Type 21, not a name. |
| You expect the same result as software at 52°N. | Latitude does not enter, so the horizon is different. | Read it as a clock correction. |
| 15:00 at 21°E should match 15:00 with no longitude. | 21/15 = 1.4, so 16.4 and another floor(/2). | Check effectiveHours before you compare. |
Before you treat the result as a reading
- effectiveHours = hour + longitude/15, then floor(/2).
- Warsaw ≈ 21, London ≈ 0, New York ≈ -74, Tokyo ≈ 139.
- Latitude and time zone do not enter.
- This is still not a sky map.
Frequently asked questions
How does this differ from plain rising sign?
The simpler rising sign uses shift = floor(hours/2). Here we add longitude/15 to the clock first, then take floor(/2).
How should I enter longitude?
In east degrees: Warsaw ≈ 21, London ≈ 0, New York ≈ -74, Tokyo ≈ 139. Range -180...180.
Does latitude count?
Not in this model. We do not build a horizon or houses. It is only a longitude nudge to the “clock”.
Why can the result differ from the no-longitude tool?
Because effectiveHours can cross the next 2-hour threshold. E.g. 15:00 at 21° becomes 16.4 → a different shift than 15 alone.
Is this a real sky rising sign?
No. A full rising needs an ephemeris, latitude and a time zone. Here you get a repeatable teaching model.
Which time format?
HH:MM in 24-hour form, e.g. 08:00 or 14:30. Hour 0-23, minutes 00-59.