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Short answer, for 1 min unfiltered exposures, about 17.9 with a 200mm f/4 and at 1.17 arcsec/px (assuming you have pretty dark Mag 20 / sq arcsec skies).
With my light pollution, I need about 5 mins to get the same result with similar equipment (see the png). Star mags on the image are from GSC2.3, which goes to about mag 20. Once you get near about mag 18 in my image, you have to use a bit of imagination to see the stars above the sky glow noise.
Attached my excel calculator, which seems to more or less agree with what I find when looking at my images. The spreadsheet also predicts what the background sky glow should be which you can check against your images (you have to convert the sensor electrons to your camera ADU units)
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