Longest shutter length for a clean moon photo?

Does anyone know the longest I can keep the shutter open and still end up with a fairly in focus moon? I'd like to get a photo of the moon just after it rises over the city skyline but am thinking my typical 30 sec shots will result in a big white blur instead of something that looks like a moon. So my idea is to stitch together photos shot at 30 sec with the one with the moon at a faster speed/higher ISO, but not sure what that speed has to be. It doesn't have to be super crisp or anything, but I would like it not to have trails.

TIA

Remember that the moon is reflected sunlight. All I've ever done is moon shots alone. Never with a foreground. For solo moon shots, start with ISO of 200 or 400. Try F16 at 1/250. That should get you a fair shot showing details of the moon. Getting the skyline is another problem. You almost have to catch it while there is still some daylight left. Might have to shoot the moon, then longer exposure for skyline and then shop them together.
I'd sure like to see the end result when you're done.

iv done it before in camera! select multiple exposure and do your long exposure! then reset compo so the moon is where you want it in the final shot and it will lay the moon wherever you want it!

The moon is moving at a couple of pixels per second ( don't recall the exact number) so for a clear shot you want a fast shutter speed - 1/50 or faster.

I suggest at least 1/180 or faster. You really need low ISO too. And use a tripod and remote firing. This all helps to minimise shake

The moon is a bright object so shutterspeeds should be rather short I would expect. Like Pierro says... Tripod is rather important as is using
low ISO. If you dont have a Tripod... Use anything you can to steady your lens. Also... if you dont have a tripod.... just remember you need
a shutter speed at least the equivlent to the focal lengh of your lens. A 200mm = 300mm on DX which means you would be looking at 500th sec
if hand held. I think a lot of people forget to take the DX into account. If you are using a tripod, this eleminates most of the need for a shutter
speed to counter telephoto efects. Use your spot meter too ! Either set auto bracketing and or use your plus and minus compensation dial.
This will garuantee a perfect exposure.