hello, I am thinking of doing some really long exposures of the night sky to get star trails with my new DSLR. To do this I will put it on bulb mode and lock the shutter open. The only limitation is that my digital camera bulb mode only goes for 8 minutes... so I was thinking after the 8 minute exposure I could take a second exposure for 8 minutes and then combine the images using photoshop. I am NOT talking about combining images to make a HDR image! How do I combine the images in photoshop to make one single image? I am fairly new to photoshop so I am looking for easy step by step instructions. Thanks heaps!