70-300mm zoom lens
Ioptron Sky Tracker.
Which will be my best bet to try imagining something easy like M42 ? What settings should I try?
Any help for the newbie would be appreciated.
Make a concerted effort to polar align the iOptron as best you can. That is going to be, by far, the primary aspect in determining how long individual exposures can be before they become trailed.
Zoom in the 70-300mm lens to maximum, close it down a stop or two. Then focus on a bright, nearby star using zoomed liveview. Use tape or something to lock the focus in place. Then point toward M42.
Initially, you want to see how long an exposure you can take without skyfog dominating, OR trailing becoming obvious. If it's cold out, use ISO1600. Else drop back to ISO800. You might be able to get 30 seconds, you might be able to get 2 minutes. Experiment. Once you find a setting you like, stick with it. Take ten or twenty such exposures (always in RAW mode), then stack them together. You'll get even better results if you throw in a few dark frames, too.
Once you a stacked and semi-calibrated result, tweak the levels and apply a steep curve to it (maximize the curve's gradient through the highest, densest part of the histogram). You may need to repeat these two steps a few times. Try not to clip the black side or the white side.
Ta da - hopefully a pleasant image with little effort.