aperture - What settings should I use to photograph aurora borealis with a wide angle f/4 lens?

I've tried my first night photography of the stars last week. Most articles I've seen were recommending a fast lens, fully opened, @ ISO 800 and about 20 - 30s exposure, etc. Unfortunately, my only "fast" lens is a 50mm f1.4 which was fine but not as wide as I would have liked.

There is a strong possibility of aurora borealis tonight and I would like to use my wide angle lens (Canon EF 17-40mm f/4.0 L USM) With maximum possible aperture of f/4.0, what settings should I use to produce reasonably noise free photo. I would like to omit star trailing if possible.

I will be using a Canon 60D DSLR.

Answer

I could make an educated guess..

Consider this picture, its EXIF data says exposed for 5 sec @ f2.8 at ISO 1600, ignoring the focal length and considering that you said most articles recommend shooting @ ISO 800 using max aperture (in your case f4) you should set your exposure for 20 seconds.
@ISO 400, shutter speed needs to be 40sec
@ISO 200, shutter speed needs to be 80sec
@ISO 100, shutter speed needs to be 160 seconds
but longer shutter speed might cause star trails.

Then again you can set the ISO to 3200 to reduce the shutter speed to 5 seconds.

Assuming the brightness of the Aurora Borealis is the same as in this picture.

I also suggest turning on the custom fuction on the 60D for high ISO noise reduction and Long Exposure noise reduction.