Startrails, stacking method with Tutorial

I have been doing a little research lately about some different methods to create night sky imagery. Mainly in an effort to improve my own night sky images. 

I came across this method of creating star trail images while looking for ways to fix my problems with exposure in star trails. Basically what you do is take a whole bunch of images on a tripod using a remote timer and then use a computer program to "Stack" the images together. This method gives you far greater control over the exposure level of the final image and allows you to get trails that are as long as you want. The more images you have the longer the trails.

I used Photoshop to create this image using some of the images I took to create a time lapse earlier last month.

Star trail created using stacked images.

Here's how.

1. In Photoshop go to: File then down to Scripts and select "Load Files into Stack".
2. A new window will pop up. Select "Browse" and locate the files that you wish to stack.
3. Select ALL of the files you want to import, click "OK". they will all appear in the use files box in the window. (Don't worry about checking the "register images" box if your images where taken using a tripod.) Click "OK".
4. Photoshop will load all of the images into a single file on many layers. This may take a while depending on the amount of images in your stack.
5. Once complete, Select all of the layers except the bottom most one.
6. In the blend mode pull down menu on the layers tab select "Lighten".
7. You should now have a whole lot of star trails.
8. Flatten the image and "Save As" something new so you don't loose any of your original images.