Advice on photo stacking

Hi

I have a Canon 350D with a standard 18mm-55mm EF-S lens. I want to take
some good wide angle photos of the milky way etc. I have downloaded
Registax to stack my photos as I do not have a equitorial motor'd
tripod (do have scope tho). Would like some advice:

1. How many photos are necessary to see objects like Milky Way (based
on exposure times used in Q3)?
2. What ISO setting should I use? (Was thinking ISO 400)
3. What sort of exposure time is necessary per-photo? (30 seconds?)
4. What format should I take the photo in (RAW or JPG?)
5. How do I stack photos in Registax? Or have you got any laternative
suggestions to this s/w?

Thanks

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