Moon rise and moon set time?

[dinhnhat0401]

Many thanks for this helpful library.
How can i implement code to calculate the moon rise and moon set time?

[mourner]

Yeah, I tried to wrap my head around this for several days and no luck... I would implement this if I knew how.

[cosminn777]

I have been looking for moonrise and moonset too. This is the only thing that is missing from this library.

[dinhnhat0401]

How about this?
http://mysite.verizon.net/res148h4j/javascript/script_moon_rise_set2.html

[mourner]

Not an optimal solution as it just loops over the whole day, finds the closest values and interpolates... I'm seeking for more of a mathematical solution, similar to the one I'm using for sun times.

[zedxxx]

It seems that there is no more mathematical method except iterations:

Practical Astronomy with your Calculator or Spreadsheet (4th Edition):

In Section 33 we found how to calculate the times of rising or setting of a star given its equatorial coordinates. We can apply the same method to the Moon to find the times of moonrise and moonset but the problem is complicated by three factors. One is that the Moon is in rapid motion so that its right ascension and declination are continually changing. To find the time of moonset, for instance, we require the coordinates of the Moon at that time; but to find these coordinates we need the time of moonset, and so we go round in a circle.

The second problem is also associated with the Moon’s rapidly changing position. In order to find the circumstances of moonrise and moonset at a given location on the Earth for a given calendar date, we need to know the corresponding Greenwich dates. We adopt an iterative scheme here, in which we find the position of the Moon at, say, midday, use that position to calculate the times of moonrise and moonset, then recalculate the Moon’s positions at those times, then recalculate the times of moonrise and moonset, and so on until the changes are small enough for us to ignore. We need to take account of the fact that the calendar date might change, and that the conversion from Greenwich sidereal time to UT (an essential step) might be ambiguous (see Section 13). And then there is the fact that the Moon might not rise or set on a particular date!

The third major complication with the Moon is that it is, astronomically speaking, very close to the Earth. The coordinates which we work out are correct for the centre of the Earth, but when we observe from the Earth’s surface the apparent coordinates change slightly; this effect is calledparallax(see Section 38). In the case of the Moon the parallax can be as much as a whole degree. Taking this into account, together with the corrections for atmospheric refraction and the finite size of the Moon’s disc (times quoted are for the upper limb), we can find the times of moonrise and moonset correct to within a minute or two of time.

[mourner]

I've added SunCalc.getMoonTimes(date, lat, lng) function in the moontimes branch. Please check it out. I'm not sure about its accuracy though — for some reasons, online calculators like WolframAlpha and TimeAndDate have times within 3-6minutes of my calculations for a couple test cities I tried. What do you think guys?

[cosminn777]

Awesome, I will give it a try!

[mourner]

Any news guys?

[mourner]

Looks like no one needs this, huh.

[cosminn777]

I am using it. It works well, no issues whatsoever until now. Thank you very very much!

[zedxxx]

The function returns an inaccurate results for my location.
For date 2014-07-05 and location 53.52, 30.20 (Belarus, Mogilev) it returns:

• 05.07.2014 10:28:28 (raise)
• 05.07.2014 21:35:16 (set)

But reference values are:

• 05.07.2014 10:23 (raise) - diff 5 min
• 05.07.2014 21:05 (set) - diff 30 min

Reference values I got from SunDroid (https://play.google.com/store/apps/details?id=uk.co.sundroid) and almost same results I see here (my tz UTC+3): http://www.timeanddate.com/moon/belarus/mogilev

And accuracy depends on date. For example, today (2014-07-09) difference is less then 5 min for rise and set and its OK.

[xqjibz]

I realize this has been a while, my testing has yielded some very good results, though my particular application doesn't require complete accuracy, I've found the times off by only a few minutes from what timeanddate.com reports. My vote is merge the PR into the main branch, so this can be used from NPM.