ESA: Small meteorite will safely impact atmosphere tonight over northern France • Hacker News Board

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#81

Post by Aachen » Tue, Feb 14, 2023, 6:09 AM UTC

tehc-uk wrote: post #66

Aachen wrote: post #41

Earlier quoted context omitted.

Would you be willing to share your exact location, perhaps in an email to sar2667observation@lgms.nl? From a sibling comment: > Got so lucky finding that Brighton video as the 2nd result earlier. Spent another 15 minutes looking for a third angle but the "looking east", "looking south" indicated angles are either implausible or too inaccurate to be useful. A Paris video is of such quality that I couldn't for the life…

https://snipboard.io/4T8Qvf.jpg Does this help at all? The line on the left is when the object first becomes visible in the video, and the line on the right is when it explodes and disappears from view - it's actually pretty similar to what you had already.

Yes, thank you! Overlaying the two, that is indeed awfully close to at least one end: https://snipboard.io/ADVdcO.jpg

What puzzles me is that the other end is so far off that it's outside what I had previously screenshotted of the map (so not visible when intersecting the two). From my POV, the angle difference between start and end was close to zero, like it came fairly straight down. That would be in line with yours if it roughly came towards me, as it roughly indeed did afaict, but I don't think the Brighton pier video had that wide a range. (I should re-watch it to be sure, though.)

There are also various reported angles on this event page https://ams.imo.net/members/imo_view/event/2023/937 but half of those honestly look in line with what I previously noticed where a video might have a description "facing east from Jersey" which would mean Paris is in the ~center of their view, not the English channel in front of Dieppe, resulting (because no visible landmarks) in lines like these horizontal/vertical ones https://snipboard.io/d3rkNI.jpg>. Compared to all that, your report is definitely more useful! It would seem the meteor traveled at least 30 if not 50 km in those ~five seconds!

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#82

Post by Aachen » Tue, Feb 14, 2023, 6:35 AM UTC

mikae1 wrote: post #72

Aachen wrote: post #21

Wow!! From just east of Aachen, perfectly visible. Turning from a point of light coming down into a "oh wow that's really cool" into an actual fireball at >400 km horizontal distance! Holy crap that was exhilarating Edit: I was expecting that it would be too far away, also with Aachen's city glow and the highway, that nothing would be visible, or at best, a point appearing and disappearing at basically the same locat…

> Quite sad it defocused Look at it from the bright side. You will never forget to manually focus the next time a meteorite passes by. :)

It's not that I forgot, actually. I considered using the "pro video" mode on my phone where I can manually set focus to infinity, but decided against it because

- I wouldn't know what shutter time and ISO setting to use, or if it should need to be adjusted during the event when I want to be watching it

- I was already fairly late to the party to start thinking about and configuring this stuff: I didn't know of the +/-1 second window at the time, only saw the 10-minute window (which was a good thing because an adjacent tweet in that thread said it wouldn't be visible even halfway here so I might not have gone out at all!)

- The phone will try to use a broader light range ('HDR') in default mode, which is not something I understand (my confusion about that is a comment in itself), but not in pro mode. It doesn't work for extremes like capturing the sun as part of any picture, but in most cases it will work as though you took two pictures with slightly different shutter times and it'll scale values and stitch the pictures so that the dark areas are not pitch black and the bright areas are not full white. That seems like something I'd not want to disable, as it might make it capture more detail of the bright parts of the event.

... but as I write this, I realize that I can select 'auto' for shutter, ISO, white balance, etc. also in pro mode. Configuring the shutter is the main reason I use pro mode for, so it hadn't occurred to me that there is also a little 'auto' button for that in the corner! Not at the time, and not at the beginning of this comment either ^^'. I can set focus to infinity and only lose "HDR", not automatic selection of other settings. That might actually be worth it, don't know. But that's a good thing to be aware of, so thanks for making me realize this :D

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#83

Post by madaxe_again » Tue, Feb 14, 2023, 8:07 AM UTC

mym1990 wrote: post #76

madaxe_again wrote: post #45

Earlier quoted context omitted.

I still do astrophotography - but nothing will ever top the broad daylight bolide I saw over France 30 years ago aged 10 or so - huge blue fireball labouring its way across the sky before disintegrating in an explosion as bright as the sun. I actually dropped to my knees in awe, the garbage I was carrying utterly forgotten.

I wonder what percentage of people will go a whole lifetime without seeing a bolide, or even a shooting star. Dark sky areas are harder and harder to come across as well, and I bet looking up at the sky for a few minutes is becoming more of a rarity as well.

Plenty. I live in a very dark sky area - about 2 bortle - and I threw a small star party for some local friends and their friends. They were astonished when I pointed out that you can see satellites, and there was some lively debate over whether the milky way was just a cloud.

It just isn’t important to most people. It’s understandable - our gods used to be in the sky - now they are on the television.

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#84

Post by dredmorbius » Tue, Feb 14, 2023, 11:28 PM UTC

cshimmin wrote: post #79

dredmorbius wrote: post #74

Earlier quoted context omitted.

The 12,000 km estimate is straight maths assuming a (fairly typical) relative orbital velocity of ~20,000 km/s for the meteroid, and looking at distance travelled in 10 minutes. Mind that the geometry of the collision might truncate that considerably. Again, I'm not claiming expertise here, and the "straight maths" rubric isn't a justification for correctness so much as explaining how I arrived at the number.

Understood! My point was that, while dimensional analysis almost always works (including for this problem), you have to make sure you are using the right dimensionful quantities. In this case that there are constraints here due to orbital mechanics that were not respected, and hence the 12,000km is way off. To successfully apply DA in this problem, we should start by noting that since we are talking about impact, it…

Thanks, appreciate the clarifications.

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#85

Post by mikae1 » Sun, Feb 19, 2023, 6:33 AM UTC

Aachen wrote: post #82

mikae1 wrote: post #72

Earlier quoted context omitted.

> Quite sad it defocused Look at it from the bright side. You will never forget to manually focus the next time a meteorite passes by. :)

It's not that I forgot, actually. I considered using the "pro video" mode on my phone where I can manually set focus to infinity, but decided against it because - I wouldn't know what shutter time and ISO setting to use, or if it should need to be adjusted during the event when I want to be watching it - I was already fairly late to the party to start thinking about and configuring this stuff: I didn't know of the +/…

> that's a good thing to be aware of, so thanks for making me realize this :D

NP :)