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Mathematical Probabilities?

goolosh

By goolosh
in The Astro Lounge

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goolosh

goolosh

Posted
Posted

Ok, i'm not a math whiz, not by a long shot. When it comes to intense calculations i defer to others.

I have a specific question regarding what i've seen when looking through my telescope the past few nights.

Night 1, while viewing a globular cluster, a satellite passed right through my field of view.

Later that night, within 1 minute of having switched to a new target to view, a plane passes right through the middle of my FOV, shocking since it was bright and took up all of my view. I literally jumped back from the scope.

Night 2, again while viewing an object, a satellite passes right through the FOV.

considering how big the sky is i am wondering what are the chances of having an occurrence with an airplane and 2 satellites 3 times within 2 days? Or is going to be a common occurrence? (If so i don't mind, was kind of cool)

TLDR: So im seeing numbers of about 13,000 satellites in orbit (both active and inactive), about 1000 plus objects to have been looking at, and about 41,000 square degrees covering the sky. What are the chances that one would have an object as small as a satellite pass right in front of your FOV?

(P.S. i was using a 32mm lens so the FOV covered a decent area)

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JamesF

JamesF

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I think that might be quite a hard problem to model. Consider that there may well be satellites in your field of view at other times, but you don't see them because they're not in a position to reflect the sun. Perhaps one way to estimate a figure might be to look at the number of satellite trails in long exposures of DSOs.

My guess is that it's not that uncommon to have a satellite or some other man-made object in your field of view. I don't notice them every day, but quite frequently nonetheless.

James

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rory

rory

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ive been observing for little more than 16 months and already had to many satellites pass through my fov to recall. very common occurance in my experience. ive not had a plane yet though.

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umadog

umadog

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"TLDR: So im seeing numbers of about 13,000 satellites in orbit (both active and inactive), about 1000 plus objects to have been looking at, and about 41,000 square degrees covering the sky. What are the chances that one would have an object as small as a satellite pass right in front of your FOV?

(P.S. i was using a 32mm lens so the FOV covered a decent area) "

Well if a typical FOV is 1 square degree (that's on the small side) then if the satellites are uniformly distributed (which they're not) then you get about a 1 in 3 (13/41) chance of seeing a satelite in any given field of view. Odds are probably much higher depending on where in the sky you're looking and at what time. Whether you're viewing a DSO or not isn't really relevent for the probabilities. The darker the skies, the more satelites you see. On a typical dark sky trip I reckon I see about 5 passing through the FOV each night. With planes it depends on whether or not you live near an airport. It's happened to me fairly often, though, including one passing in front of the sun.

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JamesF

JamesF

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I've seen a few satellites, i've also had a spider crawl into the focusser tube from the OTA, damn thing looked 80 feet tall and frightened the life out of me...

Sorry, but I laughed :)

James

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Capricorn

Capricorn

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If you viewing wide field then I would say there is a high chance of a satellite passing through your view. There are reckoned to be between 12000-15000 up there going around us.

The chance of a plane passing through is I would say somewhat less then a satellite.

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goolosh

goolosh

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I've seen a few satellites, i've also had a spider crawl into the focusser tube from the OTA, damn thing looked 80 feet tall and frightened the life out of me...

Hahahha that's awesome.

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cantab

cantab

Posted
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I've had lots of satellites pass through when I've been observing with my binoculars, which admittedly have a wider field of view than most scopes. I think it's a summer thing to an extent - because the Sun never gets far below the horizon satellites can still be sunlit, and thus visible, in the middle of the night.

Never had a plane pass through the FOV, but I guess it's not super-unlikely.

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ggreene1

ggreene1

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I'm a Newb. So far I've seen a Sea Gull and 1 aircraft pass through my FOV... But then I live in the approach to Midway Airport and O'Hare International Airport, Chicago. (That would explain the aircraft but not the Sea Gull :0) I'm sure seeing aircraft will be more frequent than satellites for me. I would love to see some satellites.

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andyc277

andyc277

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The regularity and probability of seeing aircraft depends on where you live and the direction you are looking. Ive managed to. do some calculations and worked that you are 100% lucky to see anything with the current weather. At this moment in time i can neither confirm or deny that all stars but our own have been switched off tosave energy.

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ggreene1

ggreene1

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The regularity and probability of seeing aircraft depends on where you live and the direction you are looking. Ive managed to. do some calculations and worked that you are 100% lucky to see anything with the current weather. At this moment in time i can neither confirm or deny that all stars but our own have been switched off tosave energy.

Here in Chicago we have been dealing with heat as of late, as opposed to the clouds. It hit 102 F (38+ C) 3 days in a row. Not much fun to sit on the patio with the scope if it's still 97 F (36 C) at 10:30pm. Regarding the stars... they are still in the ON position (at least on my side of the Earth) :o)

Hope you guys get some clear skies soon. Sounds like you're dying over there in the UK.

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JamesF

JamesF

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Oh yeah, I have had a bat fly past while taking an AVI of the moon...

I see bats flying about in the twilight quite often here, but I've never caught one on camera when I've been imaging.

James

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Andrew INT

Andrew INT

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I see bats flying about in the twilight quite often here, but I've never caught one on camera when I've been imaging.

James

We have a bat living near-by which I think may be a bit on the deaf side. When I'm at the EP, I sometimes get a small gathering of gnats above be. On two occations so far the bat has flown into the back of my head!

My biggest scare's todate were:

1) Looking up to see a barn own glide overhead in total silence.

2) When observing the sun, having two doves land on my back. - Mind you, all three of us jumped then!

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JamesF

JamesF

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I've had a badger creep up on me before now, but a few months back (you know, when we had weather that wasn't measured by what sort of rainfall you were getting) I set up one night was happily minding my own business when a [not-a-hen] pheasant in a tree about ten yards away suddenly kicked off. I've no idea what set him off and I had no idea he was there, but it's probably the closest I've been to needing to come in for a change of trousers.

James

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