Signs and Seasons, Days and Years

Home » Writeups » Astronomical Calendar

Astronomical Calendar

See also:
Years -5000 to -900, Regulus-oriented 
Years -900 to 3200, Regulus-oriented
Years -5000 to -900, Spica-oriented
Years -900 to 3200, Spica-oriented

Introduction

The purpose of this calendar is to bring together into one place the documentation of various astronomical events whose co-occurrences are sometimes found to be meaningful. Things currently included:

  • Dates of all new moons and full moons, including the angle of separation between Sun and moon for each case. The angle of separation provides a way to determine where eclipses are likely to have occurred. For a new moon, the separation between Sun and moon can be as much as about 5.01 degrees. If the separation was 1.5 degrees or less, the new moon may have been a Solar eclipse. If 1.4 degrees or less, it’s very likely to have been an eclipse. For a full moon, a separation of 179 degrees or more means that there was a lunar eclipse of some kind. More specifically, 178.466 – 179.024 degrees marks a Penumbral eclipse, 179.004 – 179.579 degrees marks a Partial eclipse, and 179.530 – 179.999 degrees marks a total eclipse. Note that there is some overlap in these ranges, meaning that in the marginal cases these separation angles don’t give us quite enough information to accurately predict the nature of the eclipse. If we need more precision for a particular case, this can be found at http://eclipse.gsfc.nasa.gov/lunar.html or http://eclipse.gsfc.nasa.gov/solar.html. But for the non-marginal cases – for solidly-total lunar eclipses for example, these separation angles give us all we need to determine when such eclipses occurred, and to tell us in which month of the lunar year this occurred. Colored highlighting is used to mark the type of the eclipse – total, partial, or penumbral – and the marginal cases are given the benefit of the doubt, being highlighted as the fuller type of eclipse. This means that for a few of the eclipses which are highlighted as total, on closer inspection they will be found to have actually not quite reached the total phase. Similarly, a few highlighted as partial will be found to not actually have entered the partial phase. So after having used this chart to locate an eclipse of potential interest, be sure to double-check the specifics using the links shown above.
  • Conjunctions between the following:
    • Regulus and the Sun. This marks out the beginning and end of the “year” most relevant to the occurrence of triple conjunctions of the planets with Regulus.
    • Venus & Regulus within 0.6 degree. This limits the conjunctions shown to two every eight years on the average. This comes from two concurrent 8-year series’ offset from each other by 3-5 years, with the conjunctions of one series getting a bit closer every 8 years while the conjunctions of the other are a bit farther apart every 8 years.
    • Mercury & Regulus within 0.4 degree. This limits the conjunctions shown to about two every 13 years.
    • Jupiter & Regulus within 1.5 degree. This allows about a planet-width gap at the closest approach of the planet to the star to still be counted as a conjunction. This defines the boundary between double and single conjunctions. Any larger gap than this, and a double conjunction is demoted to single. In a similar way it also defines the boundary between triple and double conjunctions.
    • Saturn & Regulus within 1.5 degree. Just as with Jupiter, this allows about a planet-width gap at the closest approach of the planet to the star to still be counted as a conjunction. This defines the boundary between double and single conjunctions. Any larger gap than this, and a double conjunction is demoted to single.
    • Mars & Regulus within 4.5 degrees. I’m not fully content with this. For the boundary between single and double I’d like to be able to use 1.5 just like with Jupiter and Saturn. But in many cases this would cause the middle conjunction of a triple to be missed. To include these, the 4.5 setting was needed.
    • Venus & Jupiter within .0167 degree. This catches just the very close conjunctions of 1 minute (60 seconds) or less. This was found to be a meaningful setting for Venus on Jupiter, so I’ve used it for the others as well. The reason for strictly limiting the output to only the closest conjunctions for Venus and Mercury is that otherwise we’d have way too much data to deal with. But it would be good to more fully investigate these cases to see if maybe some valuable data is being excluded.
    • Venus & Saturn within .0167 degree.
    • Venus & Mars within .0167 degree.
    • Mercury & Jupiter within .0167 degree.
    • Mercury & Saturn within .0167 degree.
    • Mercury & Mars within .0167 degree.

The calendar is essentially a lunar calendar, showing the dates of all new moons and full moons, and using the Spring Equinox to determine which new moon to take as the beginning of month 1. No effort has been made to nail down the precise day that each lunar month is likely to have begun. Taking the first visible crescent moon at Sunset to mark the beginning of the first day of the month, we’ll find that this typically occurs two days after these new moon dates. So just adding 2 days to the new moon dates can provide a rough approximation of when the months began. If more precision is needed for a particular date, www.TorahCalendar.com can provide that. It produces more finely-tuned results by calculating the probable actual visibility of the crescent moon.

The Equinox rule used here chooses month 1 such that the Equinox will always be between the full moon of the last month of the previous year and the full moon (Passover moon) of month 1. This gives results very similar to those of TorahCalendar.com, but probably not identical. The TorahCalendar equinox rule chooses month 1 such that the Equinox never falls after Passover, which is not quite the same as the Passover moon. They sometimes are the same, but the timing of the full moon with respect to Passover can actually vary by several days. So for marginal cases, this calendar and TorahCalendar will sometimes be found to differ by one month in where month 1 of the year begins. 

The calendar has been split into two pieces because of size limitations. To facilitate more trouble-free scrolling in the Excel Web App, after opening, click on the spreadsheet, press Ctrl-End to go to the bottom, and then Ctrl-Home to go back to the top. This fully loads the spreadsheet so that the scroll bar can work correctly.

Years -5000 to -900, Regulus-oriented
Years -900 to 3200, Regulus-oriented

The above calendars show conjunctions of the planets with the primary normal star, Regulus.
To see conjunctions of the planets with the second normal star, Spica, the calendars below are now available:

Years -5000 to -900, Spica-oriented
Years -900 to 3200, Spica-oriented

 

Advertisements

1 Comment

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: