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you should see what cosmic rays do to space telescopes public almost never sees what raw images look like RAW https://blog.galaxyzoo.org/wp-content/uploads/20
by ck2 2mo ago
you should see what cosmic rays do to space telescopes
public almost never sees what raw images look like
RAW https://blog.galaxyzoo.org/wp-content/uploads/2010/04/spiraliraw.jpg https://blog.galaxyzoo.org/wp-content/uploads/2010/04/spiral...
FINAL https://blog.galaxyzoo.org/wp-content/uploads/2010/04/spiralifix.jpg https://blog.galaxyzoo.org/wp-content/uploads/2010/04/spiral...
* https://blog.galaxyzoo.org/2010/04/12/how-to-handle-hubble-images/ https://blog.galaxyzoo.org/2010/04/12/how-to-handle-hubble-i...
they also slowly destroy the sensors since they are physical particles moving at almost the speed of light
- r_lee 2mo agothanks for the links, that's really interesting to look at do you happen to know how exactly those artifacts are cleaned up?
- shrubble 2mo agoOne way is to take a “blank” picture which will then show just the noise; then use that as a reference for what can be removed from the image.
- rbanffy 2mo agoThe blank should only show long term damage. Hits while the sensor is collecting light can be averaged out from multiple readings of the sensor.
- lofaszvanitt 2mo agophotoshop ;D, or using multiple pictures
- javier2 2mo agoits actually quite doable. any cosmic rays will not be present in two pictures in a row. any permanent damage will be exactly the same in all pictures.
- icegreentea2 2mo agoThe blog link describes the cleanup process. They take two pictures, each taking up half the total observation period. If you subtract the two images, the deltas should be the cosmic ray flashes. You can then subtract those out. They use two pictures as opposed to more to minimize the impact of readout noise. To deal with "stuck pixel" type errors, they can slightly shift the camera between the two observations. They can counter act the shift before doing the initial subtraction.
- empiricus 2mo agofunny how this also eliminates "close" fast moving objects. which I guess is a feature for a telescope
- empiricus 2mo agoI mean funny in the sense of "we did not find any anomalies, because we are careful to filter them out"
- srean 2mo agoSignal processing / denoising of astronomical images is a field of study onto itself. If you are like me you will find it super interesting. There is immense variety based upon what kind of telescope, what do you want to capture, whether it's for science or astrophotography (aesthetics). If you are into math side of things you can begin with Richardson-Lucy as a starting point and stacking.
- netsharc 2mo agoReminds me of the radiation after Chernobyl causing flashes on the physical film: https://www.youtube.com/watch?v=KOLBEx5DBaE https://www.youtube.com/watch?v=KOLBEx5DBaE
- jurebb 2mo agothank you so much for this link! I have been trying to search for footage of this phenomenon (in the pre-llm era) 10+y ago
- netsharc 2mo agoI suppose I got lucky with the search terms on YouTube, I remember watching a documentary showing the first sight of the reactor filmed from a helicopter, and the narrator saying "The flashes of light on the footage are due to radiation". I was hoping to find this heli video on YouTube, but all the "chernobyl heli" footage are from the TV series, or very very low res. The video above isn't what I was looking for, but it shows the effects of radiation very well. Sheesh, but DuckDuckGo and Google are quite useless. I just tried to see if The Internet has a record of the heli that flew to Chernobyl to shoot that first footage of the blown reactor (IIRC from Moscow, although that does not seems a plausible flying distance), and the search engines think I want to instead find out about the heli that crashed after hitting a crane...
- adonovan 2mo agoCan anyone tell whether these exposures occurred through the camera lens (from fallout particles in the sky of the depicted scenes) or in post- (or pre-) exposure handling of the film from hot dust carried by the photographer?
- matherial 2mo agoThere's no reason they would preferentially travel through the lens and hit the current frame because most of the camera and film housing is about as transparent to gamma radiation as glass. Or maybe more transparent, because glass lenses in pro cameras tend to be rather bulky. So this just happened somewhere between arrival to and departure from the zone.
- deleted 2mo ago[deleted]
- plmpsu 2mo agoOh wow, I thought those were stars at first.