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Yes your right a long exposure is needed, i setup my camera on a tripod, but if you dont have one of course you could sit it on a sturday surface, for these I generally shoot for 1 minute at least depending on how dark it is

Have fun trying it out and if you share any please tag me so I can see

I'll definitely let you know - my son will help me with this unusual photography)
I bought the tripod last month, but I haven't used it yet - now I have a reason to try it out!

Cool have fun