Orrery Moon info incorrect

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Robert
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Joined: Wed Sep 28, 2005 7:43 am

Orrery Moon info incorrect

Post by Robert » Wed Sep 28, 2005 8:31 am

I use a very sophistcated Astronomy program and I know that the Moon info in Orrery is incorrect. Orrery shows the Moon rising today at 1:44 AM for my location when it should be 2:02 AM. Orrery shows the Moon set time at 5:02 PM when it should be 5:28 PM.

The Orrery Moon icon shows the Moon setting at 4:28 PM when it should be 5:28 Pm.

Also Orrery says the Moon phase is a New Moon for 9/28/05. The Moon is currently a Wanning Crescent. The New Moon isn't until 10/3/05.

Robert :(

gandreas
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Post by gandreas » Wed Sep 28, 2005 9:44 am

First make sure that your location is correct (it uses whatever you specify as a city in the time zone system preferences panel)

Second, yes, I know it's not exactly right - the sunrise/set is usually within a minute or two of what aa.usno.navy.mil calculates, but saddly, the moon rise/set isn't quite as accurate (since lunar calculations are far more bizarre - the difference between moonrise on two consecutive days can be over an hour one day and then twenty minutes the next). I'm not exactly happy about the inaccuracy, and I hope to refine the formulas in the future.

The phase, however, includes a slight rounding to make the description match the appearance more, since techinically, the moon is only full or new for an instant. So instead, it displays whatever phase it is closest to, since that matches what you see - otherwise there would be times when you could clearly see a waning crescent even though it technically would still be a new moon.

And when I look at the orrery, it says "Waning Crescent" for 9/28/05 (and changes to "New Moon" on 1 Oct), which is extra strange since that souldn't matter where you set your location (since those calculations are done with geocentric coordinates and not topocentric).

ddilley

orrey

Post by ddilley » Fri Oct 14, 2005 4:39 pm

Why does my orrey say the correct moon phase but shows the moon with the wrong phase? For instance, it says waxing gibbous but shows a waning gibbous. Also, when will the planets come into view?

thanks

gandreas
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Post by gandreas » Fri Oct 14, 2005 7:10 pm

I'm not sure it does.

I just looked at the recently risen moon, and it has the shadow on the left side (this is the northern hemisphere, looking south-eastish).

Looking at Orerry, it shows the same thing - shadow on the left.

I can probably add planet rise/transit/set in a future version (currently the best you can do is tweak the date/fast forward time to figure out when things go above the horizon line), but there is a limit to just how much information can be shown.

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