Firstly, I think you have the makings of a good photo here. I also take your point of needing to fix the edges of the bridge, but please fix the aurora under the bridge too. You specifically mentioned whether the enhanced reflections are ok - sorry, but my opinion is not. The reason is that reflections are darker than the original light and many of your reflections produce more light than that of the bridge itself. The other problem is that the reflection intensity with respect to the source is not consistent. An example is the reflection of the bridge itself is far darker than the lights on the bridge, although the bridge roadway is nearly as bright as the lights on it.
Producing a top image from two complicated photos like this will take a fair bit of time and patience. Congratulations on giving it a go.
Karl, @Karl_Zuzarte
I use photoshop and would approach this using layers. My base image would be the bright aurora photo with the more dim photo being on top. I would mask in the dim aurora photo at about the land level, ignoring the bridge. Then I would take a second layer of the dim aurora photo and convert into a threshold mask or gradient mask (one may be better than the other). This should be able to give you the bright bridge without too much else. Paint the unwanted area of this mask black as necessary. Use the mask to superimpose the bridge on the top layer.
If you post the two original photos I may be able to play with this further next week.
