Star Trail

My first attempt at a star trail.......

Reasonably happy, there was a little bit of cloud coming across which gives the orangey streak coming in from the bottom left. Not quite sure why some of the star trails are slightly arched (particularly the ones towards the centre and slightly above). Tree in the foreground looks a rather odd, I think from reading I have done this morning I should have taken one shot correctly exposed for the tree and used photoshop to layer it in, but I don't know how to do that, so will learn before trying again!

Any advice from others who have tried this would be much appreciated!

Edit
Having gone to bed, slept, researched a bit more including finding other star trails on blip I learnt some lessons, including using wider angle to give more foreground. Happier with the result which can be seen here.