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Comment by ortusdux | Hacker News Reader

I find line scan cameras and strip photography fascinating.

https://en.wikipedia.org/wiki/Strip_photography

Early film versions used a highspeed spinning slit aperture to film fast objects. This paper from 1931 shows some very impressive results for ballistics, including the shockwave: https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.1931...

Outside sports, digital line scan cameras are used in various quality control applications (objects on conveyer belts, vehicle mounted road/rail scanners, etc). This unit can film an 8k px strip at a rate of 80khz.

https://www.youtube.com/watch?v=OXUwJOJ7fMk

View on HN

There is a similar technique in astronomy, though much slower, called drift-scan imaging. Typically when you take a long exposure astronomical image the telescope has to rotate to track the star as it moves across the sky. So in traditional imaging you track the object, make your exposure, and then when the exposure is done you read out the image. The downside is that while you're reading out the image you can't do anything else and for an astronomical CCD it can take on the order of a minute or so. So you lose ~5% of your observing time just to reading out images. (It's more if you have to slew to different locations on the sky.)

In drift-scan imaging you keep the telescope pointed at a fixed location and you continuously read out the image at a rate that matches the motion of the stars across the field of view. This allows you to continuously collect imaging from a strip across the sky.

Oh yeah I took that picture on the Wikipedia article! I have a couple more on my website [1]. One of these days I want to go to Atherton station with my line scan camera to scan some Caltrains.

[1] https://daniel.lawrence.lu/photos/

Small world! You took some amazing images. Can I ask - what hardware did you use?

Alkeria Necta N4K2-7C

Very cool. Have you thought about filming a rocket launch? The smooth acceleration should cause very a interesting distortion.

How did you buy it? Can't find any shops online. Not on eBay either.

They only do business to business sales. You'd email them and then wire them some money (about $2000 in 2017) from your company.

What does that cost?

About $2000 I think, I bought it in 2017.

Very cool photos! Just as an FYI, the link to the full sized "Victorian house in San Francisco, CA, 2020" image 404s for me.

Weird, I'll fix that later but meanwhile you can also find it here: https://commons.wikimedia.org/wiki/File:Victorian_house_on_W...

Long train is long!

It's actually hilarious what you really need to scroll it to see it on your Wiki page.

That seems to be what flatbed scanners do.

For a while, handheld scanners were a thing: hand-held strip cameras with roller wheels you would swipe across a page.

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