Yes, because I was on a fixed tripod the shutter speed has to be set low to make sure the stars are not stretched by the effect of the earth's rotation. Therefore the only option is to up the ISO. There is a rough rule-of-thumb formula for the speed.
Shutter Speed = 500 / (Crop Factor x Focal length)
So I used my 300mm lens on my OM-1 which has a crop factor of 2 Shutter speed = 500/(2 x300) = 0.8 secs
You need to up the ISO to capture faint deep sky objects.
The stacking process really helps remove the noise. I had clouds crossing last night and took over 100 images. only 47 of them were usable.
Finally, the hard part is finding the target. I used a mobile app called sky safari which is great.