Hey there! This is my first instructable so I will make it the best I can. Also, I'm not an English speaking person, so sorry for my bad English. After this little introduccion, here come the instructable.
Today we are going to learn how to make a star trail image (like the image up this lines) with a Nokia Lumia (or any phone with Windows Phone).

What do we need?

Windows Phone device (Lumia 925 in my case)
A tripod (or a solid place to put the phone)
Proshot app (Download Here)
Timelapse Tools (Download Here)
Startrail Program (for Windows) (Download Here)
A dark area far from any kind of light (better in a mountain)
A external batery (optional)
Pattience

Step 1: Setting Up the Tripod

When you get to the right place (far from houses) you have to set all up. First thing you got to do is place the tripod in a solid ground, you don't want any kind of movement at all. Then you have to atatch the phone to the tripod (I use a selfie stick piece). If you have a external battery (better for long shots) you have to make sure the cable doesn't interfiere with the phone camera. Now you can proceed to configure the camera.

Step 2: Configure the Camera

We use the Proshot app because it have timelapse feature, but if you want to make a still photo you can use the same settings on Lumia Camera.

1. For calculate the time between photos we use timelapse tools, very easy to use. fig. 1

Then we open the Proshot app. There whe have to configure some things.

First, change the mode (top right) to manual (M) fig. 2

Then change ISO to the higest (3200 in my case). fig. 3

After that we change shutter speed to the higest (4 in my case) fig. 4

We toggle flash off. fig. 5

Set the size to 16:9 (for panoramic photos) fig. 6

White balance to candlelight fig. 7

And then we make a test photo.

If the resoults is overexposed try changin ISO to lower levels.

This test photo should look like this fig. 8

If you are happy with the resoult whe change shot mode (lower right) to timelapse, and we put the interval and the durantion (and we dissable the viewfinder to save battery)

Then we eneble plane mode to save battery and we click the big AF button.

We leve it there the time we want taking care no one disturbs the camera.

Step 3: Procesing the Photos

First of all, we import the photographies to our computer to a new folder.

Then we open the Startrail program and whe click on file>open images

Then we browse our computer and we select them, then we click "Open"

Finaly we click Build>Startrail and we wait until it's comleted.

When it's completed we click on File>Save Image and we have it done.

Step 4: Optional Post-procesing

When is all finished we can trick color, brightness and contrast in our favourite photo editor (I recomend Pickmonkey). To do that we simply change values untill we have something we like.

I hope that you learned something with this tutorial, and again sorry for my bad english.

If you wanna check more of my photography check out my Flickr right here.

If you have questions it will be a pleasure to anwer them in the comments or in a post update.