RegiStax and cropped sensor Canon EOS for Astrophotography
Work in progress. (please comments in the video).
Get some very high equivalent focal lengths by using a small portion of your camera sensor to film video. Added advantage the workflow is much faster than processing raw files.
Windows box or a virtual machine.
RegiStax (its free).
ffmpeg, (very free).
Disable any in camera sharpening and contrast in the picture profile.
Magic Lantern may not be required but it is recommended.
Record at 1080p maximum ISO. (may be worth trying one lower)
Adjust the bitrate to as high as your card can handle.
Use the FPS override to shoot video at low frame rates and long shutter speeds. On my EOS M I can go as slow as 0.5FPS, and 1.5second frames.
I shot this example without a tripod.
This is the main trick to this process. The video clips will need to be converted before RegiStax can read them. I use the command line tool ffmpeg.
One clip at a time:
ffmpeg -i MVI_9683.MOV -vcodec rawvideo -an MVI_9673.avi
Add this option to do some cropping:
Size 640x480, 200,100 (x,y) top left corner measured from top left of source.
Crop in time as well if you like:
ffmpeg -ss 15 -i MVI_7467.MOV -t 10 -vf "crop=1000:640:600:164" -vcodec rawvideo -an MVI_7467_s.avi
-ss is the start time in seconds and -t is the duration.
Or all at once on OSX or linux:
for i in *.MOV
ffmpeg -i $i \
-acodec none \
-vcodec rawvideo \
$(echo $i | sed 's/\.MOV$//').avi
This will create rather large uncompressed video files that have no loss in quality.
Process in registax:
I used the default settings in RegiStax. Todo: registax tutorial.
EOS M (unmodified), Minolta MD 135mm @ F2.8, ISO 6400,
Tragic lantern: FPS override, 1/1.112, CBR 1.3x, crop mode
32frames. 1080p. Approx 7.5MB.
Below are the raw files along with a dark video if you want to try it at home without the inconvenience of buying a camera and going outside. :)