Difference
The last FITS images I made using the I, R, and G filter bands as R, G, B channels. While sorting through SkyMapper images to do this, I felt there were more satellite streaks in Z bands than any other. While I would need to look at a bigger sample to see if this is actually true, it seemed important to make images with the other bands that weren’t included in the RGB images I was creating.
As an experiment I made new frames using the Z, V and U filter bands as RGB channels. This gives two images of the same ObjectID where the stars are aligned but satellite streaks, interference, and intensity of data are different.
To compare, I’ve made images that blink between the two frames:
Sequence
A while ago I considered whether satellite lines could be used to make a drawing. Although a playful idea, it emerged again in these short loops, especially when the lines link up across frames, as in the above grid.
Without a clear idea why, I wanted to try lining up the frames in an animation so the angle of the satellite line circulated around a centre point. I chose 24 frames where the line dissected the frame, and put them into a sequence where the line moved from connecting the left hand top corner to the right hand top corner.
Then, I duplicated this sequence, reversed the order of frames, then rotated it 90 degrees and mirrored it (brain gymnastics), so that the line then travelled from corner to corner on the left hand side of the frame.
Repeating this two more times meant that the line travelled around the four sides of the frame. Most frames appear at four different angles throughout this sequence:
I say ‘most’, because an interesting part of this process what that mirroring and rotating the image created a difference that altered how the images moved in sequence. To counter this I found that it was necessary to reorder some of the frames by hand, and take some out, to create smoother motion from the new orientation of lines.
While I can’t pinpoint why this might be useful in any way (!!) it stood out to me that the process relied on reflection, and that this reflection caused unexpected angles and subsequent alterations, which I can’t help comparing to the impacts of a satellite reflecting light.