Experimenting with Star Trails and Time Lapse

Experimenting with Star Trails and Time Lapse

  August 26, 2013    Unknown

---

The weather has been a little unpredictable over the past few nights, so rather than spending ages setting up the scope and camera, I decided to stick to my Nikon J1 compact camera and do some experimenting with capturing star trails and time lapse video.

Firstly I mounted the camera on a standard photography tripod in the garden, facing Polaris. I then set the camera to manual and setup the interval timer to capture 180 x 15s exposures. It was then a case of popping back inside and watching a couple of episodes of Breaking Bad on TV whilst the camera did its job. Once complete, I then put the lens cap back on and took another 100 x 15s 'dark' exposures - the reason for doing this is so that I can capture the noise signals created on the CCD within the camera - these can then be extracted from the main images - 'lights' - in order to get a cleaner image. I can discuss this process in more detail in a later post.

Processing was fairly straight forward. I use Craig Starks' Nebulosity 3, which is available for both Mac OS X and Windows, to combine the 'darks' to create the 'master dark'. This is then subtracted from each of the 180 lights to create the processed images, which are then saved in JPEG format.

In order to create a star trail image I used a freeware program for Mac OS X, Windows and Linux called StarStaX. It is a very simple program to use - you simply select the processed images you wish to stack and select the Blending Mode as 'Gap Filling'. You can then watch the image build gradually in the preview window. Once complete, 'Save As' and that's it - you're done! Here is one I made earlier..

Star Trails - 180 x 15s exposures

Next I used the same processed images I used to create the star trails, to create a time lapse video of the stars' movement across the sky. I use Time Lapse Assembler, which is for Mac OS X, but Windows users can use a similar program called VirtualDub - both are freeware and very simple to use. Just select the folder containing your processed images and then press encode. The resulting movie file is quite large, so I used Quicktime Player to compress the file for the web. You can see the results here..

I think the star trails turned out really well considering the conditions - bright moon and light polluted skies. The time lapse worked, but I think much darker skies are required in order to pick out more stars and increase the visual impact.