Purchase and Download

I had Moon Phase Pro on my old phone - how do I load it onto my new one?

Go to the market or app store that you bought the app from originally. Sign in with the same user ID that you used for the original purchase and you should be able to re-download the app without paying for it again. If this doesn't work, you'll need to contact the particular market in question for support.

I'm trying to reinstall Moon Phase Pro on my phone. Why is Google Play now telling me it's not compatible?

There are a few rare cases where deep, unfixable problems have emerged with our app on specific devices. When this happens, our only recourse is to mark the app as incompatible with these phones on Google Play.

If you're getting a message from Google Play that your phone is not compatible, it's possible that you've run afoul of this situation. Please contact us and we'll se what we can do.

I purchased the app with a different store account than I'm using now. Can I transfer it?

Unfortunately, none of the app stores provide a way for us to transfer app purchases from one account to another.

If you purchased it through Google Play, the best way to handle this is for you to purchase the app again, send us both the original and new order numbers, and we will then refund the original order – leaving the new order linked to your new account. It sounds like a hassle, but it works out best in the long run, because you'll continue to get updates on your replacement purchase.

If you purchased the app elsewhere, such as Amazon, then I'm afraid we have even less control over purchases and accounts. Your best bet is to contact customer service for the store in question and ask them to transfer it for you.

Main Screen

I find it difficult to go forward or back just one day by swiping on the moon image. Am I doing something wrong?

Swiping is fun, but it's not the most precise way to move to a specific time or day. When you swipe, the app keeps the shadow synchronized with your finger movements, and the scales involved mean that small movements translate into large date/time changes.

To go to a specific date, we'd recommend the Calendar (just tap on a day), the Data screen (where there are buttons to move by exactly 24 hours), or the Date/Time dialog (which also lets you enter a specific time).

What does "View is rotated -31 deg from Earth" actually mean?

You'll see text like this when rotating the view off-Earth using two-finger drag. The simulation keeps the view centered on the moon, but the observer's viewpoint is no longer on the Earth, and the number of degrees simply indicates how far away from the earth the viewpoint has moved. Positive numbers indicate a viewpoint moved in the direction of the Moon's orbit, while negative numbers are moved opposite to the Moon's orbit.

Why does the moon in my app look different than in your screenshots?

Most of our screenshots, both on this website and in the app stores, show the app using an appearance setting called maximum realism. This option simulates detailed shadows of craters and mountains on the moon's surface – but it's turned off by default (it doesn't work on all devices, and the imagery used for it is relatively large). To activate it, open the app's Settings, and in the first section, tap the line that says Maximum Realism.


In the month view, can Monday be made the first day of the week?

Rather than having an option for this, the app uses the prevailing convention for the locale that the device is set for. So if your phone/tablet is set to UK (for example), Moon Phase Pro will show Monday as the first day of the week, as that's the prevailing custom there. If set to USA, it'll show Sunday.

Why does the image of the moon rotate when I select a different day on the calendar?

By necessity, the app isn't just showing you how the moon looks on a particular day, but also at a specific time on that day. For most days, the calendar depicts how the moon looks at the same time of day; for example, if it's 7:30 PM when you open the calendar, it'll show the moon at it is appears at 7:30 PM on each day of the month. And the nature of the moon's orbit is such that it appears at a different point in the sky at 7:30 PM - and this means that its apparent rotation is also different for each day.

Essentially, it's the same reason that the moon image rotates when you change the time by swiping your finger over it. It's just that the calendar shows you a month's worth of dates (and times) all at once.

Why doesn't the moon image for first and last quarters match what's shown on the calendar?

Generally, the calendar depicts how the moon looks at the same time on each day; see the previous answer for more details. This holds true for every day except major phase (new, full, and quarters). Because these phases occur at specific times (not just on a particular day), the app needs to show you the moon for those times, or the moon wouldn't be in the correct phase.

Extending the example from the previous answer, the calendar may be showing you most days for 7:30 PM. However, the First Quarter moon probably doesn't occur at 7:30 PM, but at a completely different time - let's say 5:42 AM. So when you tap on the First Quarter day on the calendar, the app will show you the moon as of 5:42 AM on that day, which is almost certainly a different rotation than 7:30 PM.

Why does your app show the new/full/quarter moon on a different day than my paper calendar?

The thing to remember is that major moon phases actually occur at very specific dates and times. Our app shows all its moon data adjusted for your local time zone, but a paper calendar isn't able to do this; it is printed with moon data for a single time zone (that probably isn't yours). So occasionally, moon phases will fall on different days according to the different sources.

What are the little icons that occasionally appear on the days of new or full moon?

We call these "badges", and they're used to signify the special moons that periodically occur:

Supermoon: a full moon period that includes the moon's perigee
Blue moon: the second full moon to occur in a calendar month
Black moon: the second new moon to occur in a calendar month

Widgets and Live Wallpaper

My widgets/wallpaper aren't working, though I can still open the app itself. What should I do?

One likely cause is that your phone has moved the app to SD card; this disables all features outside the main app. From your phone's system Settings, go to Applications > Manage Applications > Moon Phase Pro. In the Storage section of the window that opens, if there's a button that says "Move to phone" that means that the app is on the SD card – which will disable the widgets and live wallpaper. Press that button to move it off the SD card and back to the phone's main storage.

There seems to be a visual glitch with the widget. Any suggestions?

That seems to happen very occasionally when the app's image cache gets corrupted. You could try just deleting and re-adding the widget; if that doesn't help, uninstalling and reinstalling the app definitely should.

When I’m using the live wallpaper, why isn't the moon image centered on my main home screen?

Different home screens put their "main screen" (the screen you go to if you tap your device's Home button twice) in different places: some on the left, some in the center, and some on the right. Moon Phase Pro attempts to guess which is correct, but if it gets it wrong, you can override its guess in the app's Wallpaper Settings screen.


What do the terms used on the Data page mean?

Visible disc
Simply, how much of the moon's surface (as viewed from Earth) appears illuminated by sunlight.
The moon's appearance has a (roughly) 29-day cycle during which it goes from fully dark to fully illuminated and back again. The following four terms are used to describe where in the cycle the moon is.
The first half of the cycle, when the illuminated portion of the moon is increasing. In other words, a waxing moon appears larger tonight than it did last night.
The second half of the cycle, when the illuminated portion of the moon is decreasing.
A moon that is less than half illuminated (<50% visible disc)
A moon that is more than half illuminated (>50% visible disc)
How far through the moon's cycle it is, measured from the moment of new moon. The average lunar cycle is 29 days 12 hours 44 minutes long, but it varies from month to month.
New Moon
The point in the moon's cycle when it is completely dark.
Full Moon
The point in the moon's cycle when it is completely lit. Colloquially, full moon is used whenever the moon is close enough to this point to appear completely round, but astronomically, it refers to a single instant when the moon is at its farthest from the sun.
How far above (or below) the horizon the center of the moon's (or sun's) disc appears from your location. Note that the horizon here is idealized as being perfectly flat and level.
The moon's (or sun's) compass bearing as seen from your location.
Right ascension
The "x-axis" angular coordinate of the moon in the sky, measured eastward from the vernal equinox. This is the astronomical equivalent of longitude.
The "y-axis" angular coordinate of the moon in the sky, measured northward from the celestial equator. This is the astronomical equivalent of latitude.
Distance (centroid)
The current distance from the center of the earth to the center of the Moon.
Mean orbital radius
The average centroid distance as the moon goes around the earth, which is 384,399 km or 238,854 miles.
The closest approach of the moon to Earth in its orbit (363,295 km = 225,741 miles).
The furthest remove of the moon from Earth in its orbit (405,503 km = 251,968 miles).
The time when the top of the moon's (or sun's) disc appears above an ideal horizon, as seen from your location. Compass bearing (azimuth) is also shown.
The time when the top of the moon's (or sun's) disc disappears below an ideal horizon, as seen from your location. Compass bearing (azimuth) is also shown.
Zenith (aka Transit)
The time when the moon (or sun) is at its highest point above the horizon.
Nadir (aka Antitransit)
The time when the moon (or sun) is at its lowest point below the horizon.
Dawn and Dusk
Put simply, these two times are the end and beginning (respectively) of full darkness. However, there are a number of ways to define "darkness"; by default, Moon Phase Pro uses nautical twilight, the time when the sun is 12 degrees below horizontal. You can change this to civil twilight (-6°) or astronomical twilight (-18°) under Settings > Dawn and dusk;

Will the app power on my GPS if I have it switched off?

Not if you've turned it off at the device level. No app can do that unless you've rooted your device — and even then, Moon Phase Pro won't.

What are the permissions that Moon Phase Pro is asking for and why?

Here's a list of the permissions that Moon Phase Pro requests, along with a brief description of each. Click on any of them for a detailed explanation.

Moon rise and set times depend on where you are
To look up locations, and to download the imagery used for Maximum Realism mode
To store various images for faster operation
Essential to making the notifications work
Needed for full control over the app's live wallpaper

Does Moon Phase Pro give tide times?

No, it doesn't.

Although tides are intrinsically linked to the moon's (and sun's) gravitational pull, accurate tide times involve much more, being greatly influenced by the configuration of local waterways. As such, adding tides to Moon Phase Pro would greatly increase the size and complexity of the app.

For the time being, we prefer to focus on the moon itself, rather than phenomena removed from it – and leave tide tables to apps that specialize in that.