You can do this... but the "trick" is to take the shot the evening BEFORE the "full" moon moon and not the of the full moon.
Whenever you have substantially mixed lighting problems (bright moon, dark city), you usually want to look for ways to bring the radically different exposure needs closer together so that the exposure needs from the moon are not so substantially different than the exposure needs of the city. By shooting the cityscape at "dusk" instead of at "night" you are helping to bring the exposures closer together AND usually a deep blue (end of dusk) sky color looks more appealing than a black sky anyway.
The moon rises a bit later each day (since there are 24 hours in a day but there are about 29.5 days in a Lunar month). The actual time between moonrises varies a bit.
You want to be in position a bit before sunset. You'll notice that the moon actually appears to be pretty much "full" one day before it it is technically the official "full" moon. But since you are taking the shot a day early, you'll get a dusky blue sky behind the full moon rather than a black sky. On the night of the full moon, the Earth is between the Sun and Moon -- so the moonrise actually occurs "at" sunset. At that time, however, the moon will be right on the horizon and not up high enough to be visible over the buidlings in your city nightscape shot. By the time the Moon is high enough, dusk will have completely ended and the sky will be black.
By getting there a a day EARLY, there will still be some light once the Moon is high enough. This will completely change your exposure.
The Moon looks best photographed with something called the "Loony 11" rule -- which suggests a correct exposure with f/11 and setting the shutter speed to the inverse of the ISO speed. So at ISO 100 you'd use 1/100th sec if you are using f/11 (and if you use something other than f/11 you can change the shutter speed to compensate.) But this rule is for when the moon is high. Nearer to moonrise the thick atmosphere will reduce the amount of light and will likely require an extra stop to expose (e.g. you may need to slow the shutter to 1/50th at ISO 100 with f/11 - use a tripod or boost ISO speed slightly (I'd use a tripod).
Incidentally, if you use a long focal length it will create the illusion of a very large moon relative to the size of the cityscape below.
You can use the "Photographer's Ephemeris" website (or application) to your advantage here. I use a mobile app named "Sun Surveyor" but I see the folks who made the "Photographer's Ephemeris" website have also created an app. The idea behind it is you give it the location and date and it will tell you not only the rise & set times for the Sun and Moon... it'll visually plot the position angle (compass heading) and altitude angle up from the horizon for any time of the day. And they also use a map. So... suppose you want to get a picture of a city with the moon just above a specific building... the website and/or app will tell you exactly where you need to stand AND at what time you need to be standing there to get that shot with the moon precisely where you want it to be.
Photographers Ephemeris: http://photoephemeris.com
Sun Surveyor: http://www.sunsurveyor.com
Both of these do "roughly" the same thing (I first learned about Photographer's Ephemeris... but at that time the only way to use them was via their website and desktop app (which is free, btw) -- they didn't have an app. So you had to use your computer to pre-plan you shot before leaving home.) That was great -- but didn't help me on vacations where my computer is back at home.
Then I learned about Sun Surveyor (which was basically Photographer's Ephemeris... but in "App" form for my iOS mobile device.) After I bought Sun Surveyor (it's a few dollars).... Photographer's Ephemeris launched their own app. So now you have at least a couple of options.
Good luck!
Tim Campbell
5D III, 5D IV, 60Da
