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I am a bit of a beginner myself but,
1) If your guide scope is not pointing where you are imaging then in general you will be over or under correcting. Skwinty says 30% is OK but i dont believe this is true or would only be true if you were exactly polar aligned which most people are not. They use the guide scope to correct minor polar alignment errors.
So your guide scope does not have to be pointed exactly where you are imaging but close. If you are close then cone error i dont beleive would effect the corrections.
2) The benefit of using a guidescope over an off-axis guider is that you have the whole field to use to find a guide star and more light. The drawback is that if your setup is not good then you will get different rates of flexure as the mount tracks and the guiding will attempt to correct for this. An off axis guider because it is seeing what the imageing ccd is seeing does not suffer from differential flexure. However it is not so much of a roblem with widefield short focal length, more of an issue with SCT's say which even at F6.3 can have a focal length over 2 meters.
3) To me your setup looks OK. As long as it is all tied down nicely. If you are imaging through the Newt then you may have problems if the focal length of the guide scope is not close to that of the newt; as they will see different rates of error.
4) The last image is the lagoon nebula. It is just a bit dark as you dont have enough data. I have overstretched it and you can see the central part of the nebula.
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