Turning off noise reduction on canon 50d to take star pictures (1 Viewer)

Hi everyone,
I'm trying to take a few pics of the stars and star trails and have been advised to turn my noise reduction off so my pictures come out sharper, I only have the 18-55mm lens, but I can't find on my camera settings to do this! Any help on settings would be greatly appreciated as my results are pretty poor.
Thanks in advance
Dave

Hi,
Noise reduction for long exposures is covered on p176 of your 50D manual. It's under Custom Functions C.Fn II-1, and there's 3 settings. Off, Auto and On. There's another setting for High ISO noise reduction, CFn II-2.

How are you guiding your camera?

Best of luck - I gave up as the light pollution here is bad, and even going to a "dark site" about 10 miles away only dropped the pollution by about a factor of 2. It's even worse now, as many street lights are now "white" and their light can't be filtered out as it used to be when they were of an amber colour. I did find a really dark site in the Peak District, but it's a long way from Milton Keynes!