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Max The Magnificent
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Take a walk on the wild side...
Max The Magnificent   2/21/2014 7:40:04 PM
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Even if you aren't sure what the problem was, be brave -- take a WAG ("wild xxx guess")

betajet
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Re: Take a walk on the wild side...
betajet   2/21/2014 8:24:58 PM
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The term I learned is SWAG -- Scientific Wild-A*** Guess.

Without reading through all of your text, I'd say you're having a problem subtracting 7-digit numbers with 6-digit floating-point precision.  There's a reason the Unix time() function returns an integer time in seconds rather than floating point.

elizabethsimon
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Re: Take a walk on the wild side...
elizabethsimon   2/21/2014 8:27:43 PM
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the problem is that you used a sideral month instead of a lunar month (29.53059 days). The sideral month would work were it not for the fact that the earth is also moving around the sun....

But what if your inamora is affected by new moons instead of full moons?

 

Max The Magnificent
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Re: Take a walk on the wild side...
Max The Magnificent   2/22/2014 11:46:15 AM
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@ElizabethSimnon: the problem is that you used a sideral month instead of a lunar month (29.53059 days)

You've got it -- I was using the sidereal month with a value of 27.321661 days, when I should have been using the synodic month value of 29.530588 days.

When I was laying in bed working this through in my mind, I knew that my algorithm was being calculated correctly -- by a process of elimination I realized that the only factor remaining was the value I was using for the period of the monthy cycle, so I went back to the web and looked up "lunar cycles" and saw a bunch of entries, including the difference in the definitions of sidereal and synodic months.

I was both "high-fiving" and kicking myself at the same time :-)

bkeller137
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Re: Take a walk on the wild side...
bkeller137   2/24/2014 7:24:41 PM
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I agree in that my guess is the same as Elizabeth's. Since you can see the full moon dates are more than 28 days apart from the table, the period has to adjust to the approx 1/12 arc movement around the sun and so the moon has further to travel to get back to where the sun is iluminating the face of the moon that is facing the earth (approx 27.3/12 or 2.2 days). Also, you need to start with a fractional day (not Feb 14, but Feb 14.7 approx). This should explain the 3 days difference you were seeing.

Garcia-Lasheras
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Re: Take a walk on the wild side...
Garcia-Lasheras   2/22/2014 8:48:08 AM
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Here is my WAG...

Is the problem related with the reference day you took?

If the sideral month 27.321661, and if we assign a integer "label" to each full moon, there will be potential reference days that deviate from its real value. i.e. we will need to assign a real "label" to every reference full moon or, alternatively, take a a reference full moon day in which the "label" is as close to a integer number as possible.

Max The Magnificent
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Re: Take a walk on the wild side...
Max The Magnificent   2/22/2014 11:50:10 AM
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@Garcia: Is the problem related with the reference day you took?

Nope -- check out the other comments to see where my problem lay.

I've since verified my algorithm (using the synodic month) for multiple reference full moons from 1900 through to 2014 -- also I've tried it for ones that started as early as 0:13 in the morning and as late as 23:18 at night (just to check that small errors didn't creap up on me) and thus far it's worked in all cases.

Now I'm moving on to calculating the date of the next blue moon (watch thsi space).

Stargzer
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Re: Take a walk on the wild side...
Stargzer   2/24/2014 12:26:01 PM
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Max said:  Now I'm moving on to calculating the date of the next blue moon (watch thsi space).

Beware the difference between the two definitions of Blue Moon!  The newer one is two full moons in a month, the other is the third of four full moons in a season.  Also note that sometimes astronomical tables reference UTC (Uniform Time Coordinated), which is close enought to GMT for the rest of us.  So something that happens in England can be on a different local date in the US (and elsewhere!).

Wikipedia has a good discussion on this topic, including the origin of the first definition by a misinterpretation of the second in a 1946 article in Sky & Telescope magazine.  A later Sky & Telescope article (referenced in the WIkipedia article) goes into more detail.

Happy Computing!

Max The Magnificent
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Re: Take a walk on the wild side...
Max The Magnificent   2/24/2014 12:42:18 PM
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@Stargzer: Beware the difference between the two definitions of Blue Moon!  The newer one is two full moons in a month, the other is the third of four full moons in a season.

I think I'm on top of this -- I have no truck with the new definition -- I hold to the original definition that it's the third of four full moons in a season.

There's also the problem that the Maine Farmer's Almanac, referenced by a lot of discussions on this topic, defined the start of each season according to the Right Ascension of the Mean Sun -- an idealised, fictional Sun which moves at a uniform speed, giving seasons of equal length. By comparison, the start of the astronomical seasons are defined according to the actual position of the Sun against the fixed stars, which leads to seasons of unequal length. I'm going with the astronomers on this one.

Thank goodness this isn't complicated LOL

mhrackin
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Re: Take a walk on the wild side...
mhrackin   2/24/2014 2:39:59 PM
This "problem" was solved COMPLETELY about 2500 years ago.  The Jewiah calendar is  so-called "solunar"one.  To maintain the Jewish festivals in the correct seasons, and to circumvent the original method of having "spotters" to identify new moons (the demarcation that defined the first evening of each month), the rabbis came up with a calculated calendar that is based on a 19-year cycle, with some years having 12 months, others with 13. The months themselves can have either 29 or 30 days.  It's incredibly accurate, and has maintained solar and lunar average synch ever since!  Try looking up the details! It's both fairly complex in implementation, but astoundingly simple conceptually!  It actually has fewer "prototype" pages in the 19-year "perpetual" version than the present adjusted Gregorian.

mhrackin
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Re: Take a walk on the wild side...
mhrackin   2/24/2014 2:41:44 PM
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I forgot to mention that this required ONLY integer math!

Max The Magnificent
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Re: Take a walk on the wild side...
Max The Magnificent   2/24/2014 2:47:12 PM
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@mhrackin: I forgot to mention that this required ONLY integer math!

Oooh -- now you're talking my language :-)


mhrackin
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Re: Take a walk on the wild side...
mhrackin   2/24/2014 2:50:51 PM
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Or you could follow the current model and use a 19-year look-up table....  according to Wikipedia, it does lag the Gergorian by a day every 224 years, but then again, the Gregorian is gaining time on the "sol" part, with the equinox dates coming earlier.  Even the recent addition of the 400-year "leap skip" doesn't fix that completely.

Rcurl
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Re: Take a walk on the wild side...
Rcurl   2/24/2014 5:41:38 PM
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It occurs to me that the Prognosticator should have a knob labeled "Gibbous Compensation". The scale should be zero center with the extremes labeled "Wax" and "Wane" 

Max The Magnificent
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Re: Take a walk on the wild side...
Max The Magnificent   2/26/2014 1:30:53 PM
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@Rick: It occurs to me that the Prognosticator should have a knob labeled "Gibbous Compensation"

I like it -- I certainly thing we need to have a "Gibbous Compensation Function" -- just remember that anny annotations will be in Elven script LOL

Max The Magnificent
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Re: Take a walk on the wild side...
Max The Magnificent   2/24/2014 2:46:16 PM
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@mhrackin: This "problem" was solved COMPLETELY about 2500 years ago.  The Jewiah calendar is  so-called "solunar"one

I've heard of this, but I have to admit that I'd then forgotten all about it. I will take a look -- it would be interesting to see how well that syncs with my current algorithm.

Bellhop
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Grandfather Clocks
Bellhop   2/26/2014 2:51:22 PM
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Does anyone know what the makers of Grandfather Clocks did? My dad had one, but since he was always tinkering with it, I'm not sure what it was capable of.

Max The Magnificent
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Re: Grandfather Clocks
Max The Magnificent   2/26/2014 2:56:09 PM
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@Bellhop: Does anyone know what the makers of Grandfather Clocks did?

What? In their spare time?

Bellhop
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Re: Grandfather Clocks
Bellhop   2/26/2014 3:04:00 PM
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It's common for Grandfather Clocks to have a "Moon Dial" that shows the phases of the moon. I remember that the actual dial looks like a sawblade with two stylized "Moons" painted on the face. The dial was held steady by friction and a pawl poke up from the clock mechanism (from a cam?) to push the dial a notch each day.

Max The Magnificent
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Re: Grandfather Clocks
Max The Magnificent   2/26/2014 4:48:22 PM
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@Bellhop: It's common for Grandfather Clocks to have a "Moon Dial" that shows the phases of the moon.

Ah Ha! Now I see what you mean -- I tell you, they were amazingly clever in ye olden times -- now you have me wondering -- did you see the comment earlier about the Hebrew lunar calander that was calculated using only integers -- this would easily map onto using clockwork gears/cogs.

Douglas442
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Re: Grandfather Clocks
Douglas442   3/6/2014 5:53:44 AM
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Max,

Given the nature of your project, it would not be unreasonable to widen the range of applied technologies. If you have FPGA's, microcontrollers, and vacuum tubes, then why not relays and gears as well?

Anyway, clever methods for constructing astronomical clocks, orrery mechanisms, and such like have been around for awhile. Classic examples, that include Moon dials, include the 1500's era Astrarium of Giovanni de Dondi:

http://www.clockmaker.it/ingle37astrario.htm

All the way back to the Antikythera Mechanism, which may owe at least part of it's design to Archimedes. Some beautiful amateur build sites, heavy with technical details, can be found at:

http://www.cnccookbook.com/CCOrreryNotes.html

http://www.tatjavanvark.nl/antikythera/antikythera.html

And a more modern example would be the utterly awesome and astonishingly magnificent design of The 10,000 Year Clock, with funding and preparations currently underway by The Long Now Foundation:

http://www.longnow.org/

There are many horological sites dedicated to detailed examining of such builds, both amateur and professional. Fortunately, one site rounds many of these up for you:

http://www.astroclocks.nl/html/Astroclocks10.htm

---------------------------------------------------

Speaking of things that are reliable... has there been a temporary suspension or reorganization of the designlines newsletters? Mine had suddenly stopped arriving... about one month ago. ALL of them. At the same time. 

betajet
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Re: Grandfather Clocks
betajet   2/26/2014 4:41:49 PM
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I suspect clockmaker John Harrison played football in his spare time.  Why else would he have named his temperature-compensated device the Gridiron Pendulum?



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