Astro Hacker News - Full Spectrum and Infrared Photography

NoiseBert69 |next [-]

You’re considering whether it would be possible - and perhaps quite elegant - to use an XY‑scanner to raster‑scan the end of an optical fiber across a prism, disperse the light, and then capture the resulting spectrum with a CCD line sensor.

With that setup, each pixel on the line sensor would effectively record the full spectral content of the light at that scanned position, all in a single acquisition.

asdff |root |parent [-]

A problem for multispectral imagery (even within visible rgb), is that the wavelengths of light are different so the lens cannot be in focus for all spectrum at once. I have tested this out with a few of my slr lenses. If you have blue channel perfectly in focus, red isn't just a little out of focus, it is actually noticeably way out.

avidiax |next |previous [-]

One thing I've wondered about is IR fluorescence photography.

I've seen some examples in document forensics where a page that looks blank (or at least the ink is unrecognizably smudged) because of water exposure is completely legible with an infrared photo illuminated by UV.

I suspect there must be a hidden world only visible in IR and UV (and long-wave IR, e.g. "thermal").

fraywing |previous [-]

This is really cool -- pedantically, I've always thought "full spectrum" is actually misleading from a traditional photographic sense. Like IR + visible light + UV != full spectrum. I'd love to see post-processed imagery of every-day life through an extended view of broader EM energy (similar to astrophotography)... like what does a city scene look like with x-rays and microwaves included?

Side note: have always loved this image https://imgur.com/NZjWfWT of rainbows with UV and IR visible.

IAmBroom |root |parent [-]

You'd obviously have to use false-color, as most modern astronomy pictures do (even the ones that use visible tend to pump the saturation UP!).

However, the amount of light from the sun drops off exponentially away from the peak at green-blue (yellow-green, after atmospheric filtering). You'd also have to really fake the dynamic range a lot to get it to look any different from IR+Vis+NUV. (If there was 0.001% as much x-ray light as there is, say, red light, DNA could only exist in the lightless depths of the ocean.)

So, it would look like an IR+Vis photo (light falls off pretty fast in the UV, too), except the ones you've seen oversell the IR.

So it would look like a Vis-light photo, with slightly shinier objects in it.

Sorry.