The Window Sill Observatory

August 9, 2011

Making a Solar Time Lapse Movie

Filed under: Animations, Tutorials — Dave @ 2:47 pm

Step 1 – Capture Your Videos

Open DSSR and select your camera and telescope.

Centre the region of the Sun that you want to capture.

If you are controlling your scope via ASCOM you can start autoguiding by left clicking on a solar feature.

Right click on the sequence button to configure the video clip length. When you are ready to start capturing, left click on the Sequence button which will turn red and change to Stop. Click Stop when you have captured enough videos.

DSSR will place your videos in the main capture folder and they will be timestamped with the sequence start time and an index number. DSSR will also create a timestamped folder with a set of snapshot images. These images can be loaded in VirtualDub to create a quick preview video of your time-lapse.

Step 2 – Process Videos

Sort through the videos and discard any which have no details on them. For example, some videos may only show cloud cover and will stop AviStack’s batch processor.

Update: The great team at AviStack are looking into how AviStack can automatically skip any ‘bad’ videos such as mosaic blanks or clouds.

Open AviStack and load all the videos you want to process. Change post processing to manual and select the minimum area option for the saved image. I use PNG format for my saved images because it is lossless compression.

Choose a representative video and click Process File. Change the post processing settings to suit your image and then press cancel. These parameters will now be used for all videos. Now select all videos and click Batch Processing. AviStack will work through your videos to produce a set of FITS and PNG images. You can re-process your FITS files if you are unhappy with your PNGs.

Stabilise Movie Frames

AviStack will process your videos to produce sharp frames that vary slightly in size and will produce a slightly jerky time-lapse movie.

Open Dave’s Video Stabiliser (DVS) and select the sequence of processed images. Use the frame slider to review your frames and identify a feature that is present in all frames. Left click on this feature on any frame. Your video will be aligned about this anchor feature.

If your mount is AltAz, you will have image rotation from frame to frame. If you want to remove this rotation you should identify a second feature that is on every frame and away from the anchor feature. Right click on this feature in any frame.

Adjust the Similarity, Target box and Maximum drift values to suit your frames.

If there is a lot of movement between frames then check the Search whole frame box.

If the anchor or rotation features vary markedly during the animation then check the Dynamic target box.

Click the Align frames button and have a beer while DVS does its work. When it is finished you can preview the result by moving the frame slider. If you are not happy then tweak the variables and try again.

Adjust the cropping settings to suit your animation and preview the result by moving the frame slider.

Select the frame rate for your movie and click the Save aligned movie button and choose where to save your movie. You can then polish it in a video editor.

You can calculate the movie playback rate by multiplying the frame rate by the length of your original video clips. For example, 15 second clips saved at 20fps will play back at 15×20=300x real time.

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