Time lapse of stars aimed at Polaris 2019-02-08

Some more images and time-lapse video of the night sky, this time focusing / aiming towards Polaris, to directly observe the effect of the Earth's rotation on our view.
I saw a grouping of stars that seemed very distinctive, so I took a picture so I could investigate later with the Stellarium mobile app:

The diagonal reddish shape in the lower left corner is the roof of the house.  The cluster is somewhat near the middle - it's not centered because I can't see the stars through the view finder, so I was just sighting down the lens externally.

Here's what I found when I investigated the cluster:

Turns out this is the Pleides cluster, pretty well known, relatively easy to see with the naked eye.

I then took a single picture with an ~8 min exposure (largest aperture, ISO 200) aimed instead at Polaris, the north star - the other stars appear to rotate around it:

Polaris is bright star very near the center.  As you look further from the center, the stars have longer and longer streaks.  This is what you would expect for rotation with the axis rotation pointing at (or very close to) Polaris.

I then had the camera take images with 30 s exposure, about 5 seconds between shots, as many as it could until the battery ran out (got 297).  I stitched them together into a time lapse video.  In the initial version of the video I couldn't find Polaris - it was hard to find the center that the stars appear to rotate around.  So, I combined the first 10 of the time-lapse images into a single image:

I did this using the ImageMagick command "composite" - effectively adding subsequent images together:

for a in sym_links/image_00[1-9].jpg; do echo $a; composite -compose Screen "$a" screen.png screen.png ; done

Instructions here.  I took this to a further extreme, combining the first 100 images together:

I really love the perfect traces of the stars are at the furthest edges of the image, and how as you move in towards Polaris they get shorter and shorter.  I also like how even Polaris displays some motion, as expected since it is not exactly pointed at by the Earth's axis of rotation.  To be fair the apparent motion of Polaris could be due to camera motion, but then the traces of the other stars would also show an effect - an irregular jump or similar.

Using the above it was possible to identify the center of rotation / location of Polaris - so I then was able to label it in the video (best in high-def / full screen):

I also made a version of the video where I adjusted the contrast and brightness of the individual images, and then made the time-lapse video (best in high-def / full screen):

I adjusted the contrast and brightness of the original images using the ImageMagick command:

for a in *.jpg; do echo $a; convert -brightness-contrast 50x60 "$a" ../adjusted/adj_$a; done

Thanks for reading!