Hi again.

Just to stress the point one more time, a larger aperture (a small f number, like f2.8 for example) may allow you to take a picture more quickly than a smaller aperture (a larger f number, like f 5.6 for example.)

Therefore, you may wish to try and take a picture at f2.8 with ISO 800. Assuming that the aperture and ISO settings can be adjusted.

I don't know what package you are using to process your shots on your pc but if you aren't using anything have a look at some of the free packages that are available. A popular one is GIMP but I can't remember if this has a noise reduction option, but if it doesn't I'm sure that you'll be able to Google your way to some other free photo processing and noise reduction software.