questions and answers

Question?

Answer.

Q: I don't understand how to set my time zone on the moonstick. What is "UT"?

A: UT (Universal Time) is the standard time on the prime meridian. (Standard time means "not daylight saving time".) The prime meridian is the line of longitude that runs through Greenwich, England. It is the origin of the world longitude system, just like the equator is the origin of the world latitude system. So for example, if there is a new moon @ 12pm on January 1 in the Eastern Standard Time zone, then there is a new moon @ 9am on January 1 in the Pacific Standard Time zone. These are actually the same time as measured form two different places. If you use the middle mark on the left side of ruler 5, then the results are presented in Universal Time (Greenwich time). EST is 5 hours behind UT (Universal Time), so it is designated UT-5h. So if it is 12pm UT then it is 7am EST. So if you want the moonstick to just give you EST then set UT-5h on the left side of ruler 5. The middle line on the left side of ruler 5 is UT (labeled). Then next one down is UT-6h (not labeled, CST). Next is UT-12h. Next is UT-18h. Then is UT-24h (labeled). No countries of the world really use anything past UT-13h, but the marks are there just in case.

Q: How does the moon reflect light from the sun back to the Earth when the moon is so far from the Earth and the sun?

A: Yes to moon is far from the sun, about 93,000,000 miles. The earth is also about 93,000,000 miles from the sun, yet practically all of the light that we see by in the daytime comes from the sun. How does the light make it so far? Well, the earth is very far from the sun, but the sun is also very big (about 1,000,000 miles across). The proportion of the distance of the sun to the size of the sun is about 93 to 1. About the same as a regular light bulb 18 feet away. So actually the light has no problem at all making it that far. But how does it reflect off the moon and travel an additional 250,000 to the Earth. The moon receives only about 8% of the amount of sunlight the Earth receives because it is smaller than the Earth (by an approximate factor of 3.5). The moon reflects about 10% percent of the light that it receives from the sun because it has a gray color. White would reflect 100%. This light goes out in many directions. When the moon is full, the Earth intercepts only about .025% of this light. In the end, the earth receives 444,000 times less light from a full moon than it does from the sun.

Q: Are the phases of the moon the same in the northern and southern hemisphere?

A: Yes. They just look up-side-down.

Q: How are the scales applied to the rule's surface? - adhesive laminate? -surface paint? -machined grooves painted over (i.e.: scale are depressed and paint is below surface)?

A: This was actually a major source of difficulty (and stress) during manufacture. The original plans were to put the marks "below the surface". To do that, the markings have to be embossed into the mold. (Machining is very expensive.) So when the part has set, it obviously can't slide out the end of the mold, because the embossing on the mold for the markings would not let it slide. So the mold would have to separate lengthwise. But if the mold opens that way, it is practically impossible to hold the precise equilateral profile required for the rulers to slide correctly. So I reluctantly had to let the engraving go. The marks are put on with surface paint, not laminate. I do believe that the marking method does justice to the cost and general integrity of the overall manufacturing method. I have taken one slide and slid it all the way back and forth 3652 time (once a day for ten years) and the marks showed no wear. (In the future I hope to produce a more durable (probably more expensive) model, maybe out of brass.)

Q: How readily do the slides stay in place once set? -are they loose? -tight?

A: They will stay in place up to about 5 meters per second per second horizontal acceleration (about one half the acceleration of gravity sideways or about 0 to 60 in 5.3 seconds in an automobile) or about a 30 degree tilt. (I would say that they are not tight or loose, but in-between.)

Q: How are the rule's 'fixed' segments attached to each other? -screwed? -glued? -combination? -other?

A: I used a commercial adhesive. My tests revealed that the straps will likely break before they will come loose from ruler 0.

Q: How accurate is the rule? -less than a day? -days?

A: For all of the common definitions of moon phase, it will always be accurate within 13 hours. If you use the "mean" definition (which is the most fundamental definition of moon phase) it is accurate within 1.5 hours (90 minutes).

Q: Will your slide rule also determine time of sunrise and sunset?

A: Unfortunately, no. Sunrise/sunset is a very complex calculation (as you may have noticed from the demonstration on the web site). I have puzzled over how to produce such a device and have not had any real success yet. If I ever do get plans that I think are feasible, it will still be a while before the item is manufactured. (I am kind of waiting to see how the moonstick turns out.)

Q: I have a set of old scientific slide rules (you remember - the ones that predate handheld calculators). Is it possible to calculate predictions for the moon phases? -sun rises & set?

A: As far as I know, a slide rule aids in the four basic arithmetic operations, just like an electronic calculator except analog. So I would have to say that a standard slide rule would help you no more than a electronic calculator.

Q: What is a "blue moon"?

A: My understanding is that a blue moon is a second full moon in a calendar month. It happens about ever three years. (Not that unusual.) Besides, it is of no fundamental significance. "Blue moon" could better be defined as when a calendar month straddles two lunar months so that it contains the full moon from both.

Q: In the calculation for sunrise etc. what do you mean by old & new Style?

A: In the year 1582, ten days were omitted, resulting in a year of only 355 days. The rules for leap years were also changed at this same time. After this change, the calendar is referred to as New Style (NS). Before, it is referred to as Old Style (OS). Almost all countries today use the New Style Calendar (including the US).

Q: How does the position of the moon change relative to the horizon features?

A: The general motion of the moon through the sky can be understood with a simplified Earth/Moon/Sun model. The orbit of the Earth around the Sun and the Moon around the Earth are in the same plane. But the rotation of the earth is tilted to this plane by 23 degrees. Thus the northern hemisphere leans one way (approx. toward Cancer) and the southern hemisphere the other way (approx. toward Capricorn). The earth orbits the sun in 365 days. The moon orbits the earth in about 27 days. Proper interpretation of this information will lead to the following conclusions. The moon passes between the Earth and the Sun about every 29.5 days. The moon passes thorough the northern hemisphere about every 27 days. Thus, in a days time, the moon will rise in the east and set in the west much like the sun. When the moon is between the Earth and Sun, the moon will rise in the morning and set in the evening. When the moon is on the other side of the Earth, it will rise in the evening and set in the morning. Also, when the moon is in the northern hemisphere, it will travel across the sky like the June sun. When it is in the southern hemisphere it will travel across the sky like the December sun.

Q: Relative to the sun, how does the moon's position change?

A: At the beginning of the cycle of 29.5 days, the moon will be very near the sun. Then about a week later, it will be about 90 degrees east of the sun. Another week and it will be about opposite the sun, 180 degrees away. Then after about another week it will be about 90 west of the sun. And then after another week the moon is very near the sun again and thus the cycle repeats.

Q: How does any variation relate to the phase?

A: When the moon is between the Earth and Sun. We obviously are viewing the unlighted side of the moon. When the moon is opposite the sun, the moon is obviously lighted from the front and appears lit up. When the moon is 90 degrees from the sun, we would see half of the dark side and half of the bright side.

Q: I am a minister in a church which keeps the biblical Holy Days (from Leviticus 23), which are based on observed lunar events (new and full moon). My question this: Is the full moon an occurrence that is first observable at one place (Time Zone) on earth and then wraps around to the other time zones as does the setting sun, or is it somehow different?

The reason I ask has to do with when a Holy Day (which should commence with the full moon) should be kept. I believe that it should be kept when the observer sees it in the location (TZ) where he is, while another believes the day should begin when the full moon is observed in a fixed place (e.g., Jerusalem) and then everywhere else around the earth as that day comes to them.

I believe this would cause one NOT in Jerusalem to observe the day either before or after the full moon has occurred in his local area. The other person believes my way would cause the day's observance to span two earth days before everyone observed the full moon and hence, the Holy Day.

So again, does the observance of the full moon occur everywhere on earth within a 24 hour period or does it actually take two days for it to be observed by every time zone on earth?

A: The short answer is "yes, it take 24 hours from the first sighting of the full moon until everyone has seen it. (see below, actually this is wrong)"

Let me play out both methods for you so you can be sure you understand.

These example apply to latitudes 60°S through 60°N. In the "polar" regions the exact sequence of events would be more complicated.

First of all, we will define a full moon to be a moon that rises after the sun sets.

Method 1 "Everyone observes the holy day based on local observation" If the moon is 5° north of the ecliptic (which is regularly the case (about every 11 months)), the first people (between 60°S and 60°N) to see the FM will be at 60°S on the longitude where the sun happens to be setting when the FM first becomes "available". Actually now that I am working it out in detail, I see that these people could see the full moon first. Then it could take 36 hours or maybe longer for the first sighting on the equator. And then another 36 hours to be sighted at 60°N. And then another 24 hours for everyone a 60°N to get a chance to see. So if we add all that up, it looks like it could take as much as 4 days from the first sighting (between 60°S and 60°N) until everyone (between 60°S and 60°N) gets a chance to see. Okay so maybe I was wrong.

Now you could define full moon by a different definition. Now lets say the moon is full when it is the brightest. This would occur everywhere on Earth in less than 4 hours. Then within 24 hours, every one would get a chance to see it. Back to the old definition now.

Method 2 "Observation is based in Jerusalem. When Jerusalem sees the moonset after sunset they signal the world that holy day begins on the very next sunset (which is occurring immediately in Jerusalem). The beginning of Holy Day would then circle the Earth to the West following the sunset terminator. In about 24 hours the sunset terminator would return to Jerusalem. Now, just for an instant, Holy day would be in progress everywhere on the Earth. But immediately after, holy day would end in Jerusalem and given another 24 hours would be ended every where on Earth. This method presents a strange side effect. The people just east of Jerusalem would always celebrate holy day on the "following day". As you can probably see from the example, their sunset will occur just before that in Jerusalem, but they can't begin holy day until Jerusalem gives the OK. So even if Jerusalem gives the OK, their sun has already set and they will have to wait until the next day to celebrate holy day. Oh well, nothing is simple. Is it?

Q: Please allow me to ask one additional follow-up question. You said that if one defined the full moon to mean when the moon is at it's brightest, then this would occur within 4 hours everywhere on earth and then within 24 hours everyone on earth would get a chance to see it. This actually might be the answer to my dilemma. Could you explain this in a bit more detail for me? And also in this case, what would be the best way to determine when this occurs? I am especially interested in a method which I could use to predict into the near future (next 5-10 years). Are there charts available or a formula or other source (e.g., Old Farmer's Almanac)?

A: Hmmmm..... brightness is not something that could be easily determined from just looking at the moon. You would need special photometric equipment because human eyes just aren't that accurate. Also you would have to correct for atmospheric conditions. Exact calculations to predict brightness would be complicated at best.

If you are looking for a no complications, easy to predict definition of full moon, may I suggest mean ecliptic longitude (or right ascension (it doesn't make a difference)) of the moon minus that of the sun. This definition is completely immune to human convention or particulars of the definition. In fact, the mean "ecliptic longitude opposition" and the mean "right ascension opposition" and the mean "brightest moon" and the mean "first moonrise after sunset" are all at the exact same time, this is the time of the definition I now speak of. This is really the only argue proof definition. If you use this definition to tabulate the times, and then compare those to an almanac you will probably notice (depending on the almanac definition) that the almanac times are 12 late and then 12 early, swinging back and forth in cycles of about 12 months. The "mean" definition is on average, right on time for all other definitions. The mean moon phase is also very easy to calculate. Every mean full moon is exactly 29 days 12 hours 44 minutes and 2.9 seconds apart. The formula for full moon is .5=.20439731+t×.03386319269. Where t is the number of days after the beginning of the third millennium Universal Time. (Third millennium begins 12am January 1, 2001.) You can find this formula in the Moonstick Instructions on the website. The easiest way (I know of) to apply this formula is with the moonstick. You can figure all of the full moons in a year in about 2 seconds.

In my last message, change "12 late" to "12 hours late" and "12 early" to "12 hours early".

Q: What is a second new moon in one month called? On July 31, 2000 there is a second new moon in the month.

A: I don't think there is a special word for such a moon. Probably best to just call it "the second new moon in a calendar month".

Q: what is the waxing phase of the moon?

A: Waxing (as referred to the moon) just means that it is getting brighter as viewed from the Earth. Waning means it is getting dimmer (as viewed from the Earth).

Q: does this happen every month?

A: Yes. The moon waxes for about two week and then wanes for about two weeks. Then the cycle repeats. Wax, wane, wax, wane, wax, wane, and so on forever and ever in a cycle that averages 29.530588 days.

Q: Can the Moonstick be used to tell time? Your page says that the time of moonrise and moonset can be determined by the phase, and if one can estimate how far along the moon is between those two times, then its a "moon dial", right? I've seen references in popular fiction to outdoorsman knowing the time of night based on the phase of the moon, but I've never seen or heard that explicitly stated.

A: You can (in fact) tell time at night using the moon phase and moon's position in the sky. First you must imagine that the moon is the sun and then guess what time of day it is. If you have a sun dial, you can read the supposed time of day from the moonlight shadow just like you would for a sunlight shadow, but this is (of course) not the actual time. You would then take this time and add the hour angle of the moon plus 12 hours. So here is the amounts you would add to the time read on the sundial depending on the moon phase.

new moon: add 0 hours
first quarter: add 6 hours
full moon: add 12 hours
last quarter: add 18 hours

So here is an example. The moon is first quarter, and the moonlight shadow shows 5 p.m. on a sundial (the moon appears to be in the sun's 5 p.m. position). It is (of course) nighttime or you wouldn't be able to see the moonlight cast a shadow. The current time is 5 p.m.+ 6 hours (because of first quarter moon phase). So the actual time is 11 p.m.. (This method can be off by about 30 minutes. In addition, your watch is probably set to the time on your standard time zone meridian (75°W for EST) and not the actual time where you are. Also, your watch is probably another hour ahead because of Daylight Saving Time.)

Q: What is the Moonstick made of? Plastic, wood, cardboard?

A: Plastic, specifically, ABS.

Q: As I am interested in computer calculating moon phases, do you have , or know of, any algorithms for calculating the phase of the moon for any year (certainly within plus or minus a hundred years from now, with say, an accuracy of up to a day or so ?

A: There are many definitions of the primary moon phases (full, new, etc.). These definition always agree within about 12 hours. So for your accuracy requirements ("up to a day or so"), the definition won't matter much. The moonstick definition ("mean moon phase", which I think is the most fundamental definition anyway) would be a good choice. The easiest way (that I know of) to apply this formula is with a moonstick. But assuming you want to program it into a computer, here is the raw formula. moonphase = .20439731 + t × .03386319269/day + t² × .301E-14/day² where you interpret "moonphase" as follows .00=new moon .25=first quarter .50=full moon .75=last quarter and "t" is the time after the beginning of the third millennium in the Greenwich time zone (2001jan1 0h UTC). If you know how to apply this, great. If it doesn't make sense, let me know and I will fashion it into a easier-to-apply less-versatile algorithm.

Q: What factors affect the rising and setting of the moon? Is it the solstice and equinox?

A: The factors that effect the times of moonrise and moonset are (in order of importance, assuming you are in the mid-latitudes): moon phase (knowing just the moon phase will get you within an hour or so) season (correcting for the effects of the season will probably get you within 30 minutes) location of the lunar perigee (correct for this also and you will probably hit it within 15 minutes) location of the lunar ascending node (now probably within 5 minutes)

Q: I have been searching and trying to find information explaining when you have a full moon, what does it do to the body, or brain to change a person mentally?

A: The main two direct ways that the full moon effects the Earth are the tides and nighttime illumination. The tides (spring tides) are also present with the new moon and have no direct effect on you if you are not near the coast. The other factor (nighttime illumination) is responsible for most behavioral changes in humans and animals. Humans are (obviously) more adventurous during a full moon. Mt. Everest was first summited during a full moon. William the Conquer invaded England in 1066 during a full moon. I think practically all military invasions occurred during full moons. Let me see if I can think of some more. Battle of Marathon, let me find it. Just says September 490BC. Oh well. I must be "brain dead" this morning because I can't think of any more. If you could supply me with the names of some military invasions, I will be glad to look up the date and determine the moon phase. I have also heard that women who spend enough time outside have their menstrual cycle become synchronized with the phases of the moon. (No first hand knowledge here.) I have also heard that their are more births during a full moon. Additionally, I have heard that the disposition of the mentally ill drastically change during a full moon. I wish I had more first hand knowledge to share with you.

Q: Thankyou so much for taking the time to reply about the moon. I have been told that it does something with gravity, and even changes dispositions with the not mental ill people. They get a little augumentive.

A: Yes, it has a lot to do with gravity. That is what causes the tides. You might like to read http://www.moonstick.com/tides.htm.

Q: can you tell me how to calculate exactly the date and time of each moon phase?

A: Yes, I can show you how, but first I must know what definition of the moon phases you prefer. Mean phase is relatively easy to calculate. Phase based on difference in ecliptic longitude is somewhat harder but still manageable. Phase based on angular separation is about the same difficulty. Phase based on difference in right ascension is harder still.

Q: I only need to calculate the mean phase to know at what time does it begin.

A: Your question is specifically what the moonstick is designed for. If you prefer a symbolic/algorithmic method instead, you can use the mean moon phase formula directly from the moonstick instructions, http://www.moonstick.com/instructions_page_2.gif. Look in the right column under "Specifications"; then find "source formula".

Q: Is there a formula to manually by hand figure out the phases of the moon? If so what is the formula?

A: You may find your answer at http://www.moonstick.com/in_head_2000-2009.htm or possibly at http://www.moonstick.com/in_head_2000.htm. There is also a raw formula in the moonstick instructions at http://www.moonstick.com/instructions_page_2.gif. Look in the right-hand column under "Specifications".

Q: What is a Raven's Eye Moon ???

A: I must say that I have no idea what a "raven's eye moon". Don't know what else to say. It's new to me.

Q: Where can I buy?

A: Right here. We have a page that gives most of the details of buying, http://www.moonstick.com/distribution.shtml .

Q: Can you please tell me why does the size of the moon appear different at different times each month?

A: The apparent size of the moon varies from about %5 smaller than normal to about %5 larger than normal. So the difference is not very large. The reason is rather straight forward: The moon is sometimes closer to the Earth than at other times.

Q: I was wondering if you could tell me what the phases of the moon are called.

A: You may find the answers you need at http://www.moonstick.com/moon_phases.htm.

Q: When did you have the idea, when did you have the first prototype and when did you start production?

A: The big part of the idea (the shape) came to me on September 23, 1997. First prototype came within a few days if not on the same day. Production out of plastic began (?) in August of 1998. (Don't have the records with me.) Didn't get production methods right until (?) October 1999. Wow, that's more than a year. Maybe it was that long. We started the web site in December 1999 (?).

Q: Do you have a book in America, similar to our Paul Ahnert "Astronomisch Chronologische Tabellen"?

A: The book I use is called "The Astronomical Almanac for the Year", printed by the combined efforts of US and England. It's sounds similar to the book you mention but a little more technical. It gives a simple formula for the moon phase, but they don't call it moon phase. They call it "mean elongation of the moon from the sun measured along the ecliptic to the mean ascending node and then along the mean orbit of the moon". That is still just the moon phase, but a more technical way to say it.

Q: Why is the sky blue?

A: Of course for an oscolating electric dipole, the radiated energy is proportional to the square of the charge acceleration, and since the polarization of air is directly proportional to the applied electric field, then the charge acceleration density is proportional to the second time derivative of the electric field, which is obviously proportional to the square of the frequency for an incident EM wave of a given energy density. Thus the dispersed energy is proportional to the forth power of the frequency and EM waves in the 375nm range are scatter by the atmosphere 16 times as much as EM waves in the 750nm range.

Q: We have a running debate at work. Please help settle it. Are the phases of the moon caused because the earth comes between the sun and the moon and thus causes parts of it to be covered as it moves through its "phases". Or are the phases caused because we see the moon from different angles and each angle reflects back a different amount of sunlight?

A: Well, these are actually both reasons that the illuminated part of the moon appears to change size and shape. The first reason ("because the earth comes between the sun and the moon and thus causes parts of it to be covered") is called a lunar eclipse and only occurs for about 2 hours twice a year. The second reason ("because we see the moon from different angles and each angle reflects back a different amount of sunlight") is what is commonly termed "the phases of the moon"; it runs a regular cycle of 29.530588 days. You can read http://www.moonstick.com/moon_phases.htm for a better explanation of the phases of the moon. The "phases of the moon" are easy to predict because they follow a regular cycle. The lunar eclipses, while occurring about ever six months, are much harder to predict and are only relevant for a few hours. So I suppose your answer is #2. For the vast majority of the time, the appearance of the moon is changing "because we see the moon from different angles and each angle reflects back a different amount of sunlight".

Q: Is there a full moon every month?

A: Not necessarily every calendar month, but every 29 days 12 hours 44 minutes and 2.9 seconds. So, as you can see, some Februarys might not have a full moon.

Q: Is the moon the only star, planet or satellite that experiences phasing? and Why?

A: Actually everything experiences phases except for things that produce their own light (like stars). This means that the Earth, Moon, all of the planets and their satellites, and asteroids all have phases. Stars (the sun included) do not have phases. Most people don't think of the Earth as having phases, but it does. The cycle of night and day are the phases of the Earth. The cycle of new moon and full moon are (of course) the phases of the moon. Phases simply mean that the subject is under different lighting conditions at different times. The moon (for example) is call a new moon when it is lighted from behind. It is called full moon when lighted from the front. When the Earth is lighted from above, it is called daytime. When lighted from below, it is called night. The planet Venus has notable phases. Through a telescope, it can be seen lighted from all sides, front, and back. Mercury too. The superior planets (like Mars, Jupiter, and Saturn) have phases too, but they are not very noticeable. They are generally always lighted from the front as viewed from the Earth.

Q: Now, let's consider how much kinetic energy is dissipated as heat and other forms of energy when this body of 1 km. diameter, density 3000 kg/m3, and moving at a velocity of 10,000 m/sec impacts a body like the moon (where we can neglect atmospheric effects).
k.e.=(1/2) (mass) x (velosity)to the 2 power
watch your units
k.e.= how many joules?
to get an idea of how much energy this really is, consider that 1 megaton of tnt (that's 10 to the six power of tnt) is equivalent to approximately 4.2 x 10 to the 15 power joules. How many megatons of tnt are equivalent to the energy released by our typical hypothetical impacting body?

A: 3000 kg/m3: about the density of rock (right?)
10000 m/s: reasonable for an asteroid
1km diameter: sounds pretty big. look out!!!!

volume: .524E9 m^3
mass: .157E13 kg
speed: .999E4 m/s
kinetic energy: .784E20 J
equivalent to: 18 thousand megatons of TNT (holy cow!!)

Just going on memory, I think the Hiroshima bomb was .02 megatons and completely destroyed everything within 2 km. So you might guess that this type of explosion would destroy everything within 200 km. But I could be completely wrong.

When will you be making a sun stick for sunrise and sunset?		I've been working on plans for quite some time, but there seems to be some serious design difficulties. It may be unfeasible in the end. As you know, moon phase is a relatively simple calculation. Moon phase progresses at a relatively linear rate. It is the same everywhere on Earth except for time zone. Sunrise/sunset calculations (on the other hand) are very complicated, as you may have noticed from the demonstration on the web site http://www.moonstick.com/sunriseset.htm.

I have a question about the phases of the moon and lunar eclipses. How do they differ? In other words, what causes a lunar eclipes and what causes a new moon?		Both a lunar eclipse and a new moon cause the moon to look dark (as you said), the key to their difference is in what causes the darkness. For a new moon, the darkness is because the moon is lighted from the back. Kind of like trying to take a photo when the light is coming from behind your subject. It makes the front dark. The back is nicely lit, but no one can see that. For a lunar eclipse, the darkness is because the moon is in a shadow (the shadow of the Earth). So it is dark on front and back, but looks basically the same as a new moon. Kind of like when you are trying to take a photo and the shadow of your head falls on your subject. The moon orbits the Earth in such a way that it passes alternately near the shadow of the earth and on the sunward side of the Earth. The moon will often just miss the shadow of the Earth and thus not have a lunar eclipse. But you have the new moon effect ever trip round the sunward side. You might also like to read this, http://www.moonstick.com/moon_phases.htm.

We are looking for dates (with exactly time) from moon conjunctions (new moons) for as larger period as you can get or give us.		When you say exact time. How exact do you mean? Hours, minutes, seconds, even better? Also tell me, what years are you interested in? Past, future, how long? I can provide this information for you. The answers to these questions will help me know better what you need.

1.- When I say exact time, I am referring to hour, minutes and, if is possible, seconds. 2.- If is possible, I would like to get this data from 1960 to this year (past); and taking advantage of your help, the projection for the next 19 years (future). I am comparing the calculations for Hebrew calendar versus the real time of new moons (conjunctions) for a period of time.		You know, the definition of new moon is something that is not universally agreed on. And different definitions give different results on the time on new moon. When I look it up in the dictionary, it gives two conflicting definitions (one based on ecliptic longitude, the other on right ascension). The definition that I prefer (and the moonstick uses) conflicts with both of these. There are also other common definitions. So tell me, which definition do you like? Let me know, then I can do the calculations and send you the results.

Well, I really don't know what is the best definition for the new moon or the conjunction, but I understand that when the moon is in between of both the Earth and Sun, and these three are exactly aligned in the same plane (not in a line), there is a new moon or a conjunction. Please, suggest me what is the best definition that you know compatible with the explanation above.		Well see, that is just it. If you can remember basic geometry, three points in space are always in the same plane. For example, if you pick two points in space, I can put a plane through them both. But I can now I can spin this plane about a line running from one point to the other, and still keep both points on the plane. Thus I can spin the plane to include any third point of my choice. Lets see, you said you were trying to compare to the calculations for Hebrew calendar. So all you have is the results of those calculations, you don't know what there original definition was. Right? <Please, suggest me what is the best definition that you know compatible with the explanation above.> There really isn't one. Suggest another definition and I will tell you if we can make sense of it.

Good point. Well, the antic Hebrew people knew the moon cycle; in a certain time the moon was not visible to them, because it was in between the Earth and Sun (there was a conjunction). As this event is not always visible in Israel, they marked the new month (new moon) when the moon was just a little nail (almost 1 day after the conjunction). In the modern time they have a calculated time from "molad" to "molad" (month start) in which express the exact time (hours, minutes, seconds....) of this period. Now, do you know what is the definition for a new moon used in the Gregorian calendar? I think is the same. I really don't know the technical definition, but I think you can help me.		The Gregorian calendar makes no definition of new moon. In fact, it does not even recognize the moon. It sounds like you need a definition based on visual conditions in Israel. This can be done, but the results will have no relevance to the rest of the world. May I suggest "mooncalc". As you can see here, http://www.starlight.demon.co.uk/mooncalc/mcalc5_wm3.gif, it will show you the locations of the first moon sighting each month. You can download it from here, http://www.starlight.demon.co.uk/mooncalc/.

It seems to me the math doesn't handle the phase shift due to eccentricity of the Earth's and Moon's orbit.		Your absolutely right there. The moonstick computes mean moon phase. This makes the length of each month exactly 29d 12h 44m 2.9s. Thus moon phase computed by the moonstick can differ by about 12 hours from other common definitions of moon phase. The incorporation of the leading and lagging due to eccentricity seemed unattainable during design. Additionally, these definitions are somewhat ambiguous, not agreeing on weather to use right ascension differences or ecliptic longitude difference or something else.

Did you consider making the moonstick a circular calculator? Not quite as compact, and you would probably need multiple disks of the same size since you use allthree sides of the triangles.		We though that the only conceivable way to make it circular was to not be able to change sides. We developed a marking scheme that accomplished that, but it was very overwhelming to the eye. Imagine all of the marks on one side. (Ouch.) And like you said, not as compact, so we decided on the linear arrangement. But you are right that moon phase is a fundamentally cyclical calculation, indicating that the calculator should be circular. The circular design just had too many down falls that it wasn't worth it.

How do you tell time of day without a watch?		In the middle of the day, you use method 1. In the morning and evening you use method 2. METHOD 1 First mark the shadow of something. Now wait a few minutes. Now mark the shadow of the same thing again. Put your left foot on the first mark and your right foot on the second mark. Now you are facing north. Or there abouts. Error is the worst far from midday and far from equinox. Alternately use a compass to find north. I have one on my wristwatch. :) Now close one eye. Look at the shadow of your head on the ground. Imagine where in that shadow your open eye would be (somewhere on your head). This is reference point 1. Now, given that you are facing north and know your latitude and the season, you have to find the location of sunrise in the exact opposite season. This is reference point 2. Now following the path the under-horizon sun would take in that season, measure the distance between your reference points with your arm stretched out, pinky sticking out, thumb pulled in. This is the number of hours till sunset. METHOD 2 Just look right at the sun and measure with your hand along the appropriate path to the horizon. Appropriate path depends on season and latitude. (of course this method can be inverted to determine hours after sunrise)

You have to first calculate the time of sunset in your head (something I have become quite good at) and then you use "the method" to tell how many hours before sunset it is. And thus the time. You'll have to tell me more - I know the sunset formula, but how in your head?		Basically, the sun sets at 6pm (18h). First add the correction for your latitude and the declination of the sun. When the sun is at full declination, the corrections are 0° latitude - 0 hours 30° latitude - 1 hour 50° latitude - 2 hours 60° latitude - 3 hours (and 15 minutes) When the sun is at less than full declination, interpolate appropriately. Then add the equation of time. 10 minutes for the obliquity and 7 for the eccentricity. Obliquity of course goes, 0 west 0 east 0 west 0 east 0 from winter sol. to winter sol. Eccentricity goes, 0 west 0 east 0 from aphelion to aphelion (July 4 or there about) And finally your offset from standard meridian. And Daylight Saving time if you prefer. EXAMPLE My old house (30N 85W UT-5h). April 21. 18h00m Full dec. correction for lat. is 1 hour. But its only April 21, so use half (sin 30 degree). +0h30m Equation of time about 8 min for obliquity about 6 min for eccentricity +0h08m -0h06m And I'm 10 degree west of time zone +0h40m GRAND TOTAL 19h12m (7:12pm) As you can see, this method employs "hand waving" math and is not rigorous, but you can also see how it can get you quite close to the answer. (BTW, throw in 3 or 5 minutes for semi-diameter/refraction if your really picky. :) )

i want to know why does the duration of day varies at a particular place and varies from place to place?		Imagine the Earth, as you would see a globe, set on a stand so that it can turn about a tilted axis. Now imagine the sun. The earth will circle the sun like a horse on a merry-go-round. Now note that the Earth is spinning much faster than it is circling the sun. In fact, the Earth spins more than 366 times in the time it takes it to circle the sun. Now focus on your Earth. It is spinning on a tilted axis. So if you have the top tilted to the right, then a city in the northern hemisphere will spend more time on the right side of the globe than on the left. My city for example (Quincy, Florida, USA) spends about 14 hours on the right side and then about 10 hours on the left side and so forth and so on. If the Earth is on the right side of its circle around the sun, then it will be night for 14 hours and day for 10 hours. If it is on the left side of the sun, then it will be day for 14 hours and night for 10 hours. Cities on the Equator spend 12 hours on each half, so there is no seasonal change. London spends about 16 hours right side and 8 hours left side. The north pole is always on the right side 24 hours per day. Sydney, about 9 on the right and then 15 on the left. Making sense yet? So the hours of daylight in any particular place depend on (1) how many hours that place spends on each side of the Earth and (2) which of those sides the sun is on.

what is the terrestrial longitude of observation and how do i get it?		That is your longitude. I'm in Quincy, Florida, so my "terrestrial longitude of observation" is 84°34'W.

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