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Question: what’s your rate of visual satellite transits?

moon observing solar
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#1 Jacob.Redshift

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Posted 20 September 2019 - 09:01 PM

Hi All,

 

I’ve been staring at the sun again... safely of course!

 

I noticed several satellite transits across the solar disk during my observing.

 

The first was pretty big (probably 40 or more arc seconds) and fast (probably under .5 seconds), and I could definitely see some angular (as in jagged, not as in degrees of size) sort of shape to it. Very cool one.

 

The second one was tiny and slower, round, probably 25 arc seconds in apparent visual size, and a full 1.5 seconds to transit the solar disk.

 

The third was medium to small (35 arc seconds) boxy looking, and also 1.5 seconds to transit.

 

These are all of course my best estimates, as I wasn’t imaging. 

I’m comparing in my mind what I saw today to the three ISS solar transits and one lunar transit that I’ve seen and photographed in the last year, knowing what each of their respective angular diameters and transit times were for those events.

 

It’s always neat to see a satellite through the scope, but what most surprises me is the number I saw in the time that I did. I probably had 25-30 minutes of total time with my eyes actually observing through the eyepiece. 

 

So, that brings the question... what’s your rate of satellites in the eyepiece? —and I mean the unplanned observations of them. 

 

1 every ten minutes seems high, but that’s where I was today.

 

Last night I got one wizzing across the eyepiece while staring at Jupiter. probably had roughly 30 minutes on the eyepiece, so my rate was lower. 

 

I have never kept track, and I wonder how it will average out over time.

 

Anyone have a log where they have some long-term numbers?

 

Just one of those nerdy astronomy questions about which I’d love to hear others’ accounts.

 

 

 

 

 

 

 


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#2 db2005

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Posted 21 September 2019 - 01:34 AM

I haven't kept a log of satellite observations, but if you say it happens once every 10 minutes O would say that is probably in accordance with my own experiences, perhaps even a conservative estimate. Of course, some locations of the sky may be more "active" with satellites and of course the probability of seeing a satellite passing through the field of views depends much on the real field of view, so less satellite observations are to be expected when observing at high magnification. I also occasionally see "faint" satellites when observing through the eyepiece, satellites which probably wouldn't be visible to the naked eye alone. One particularly memorable observation happened last year when I saw a faint object approach and pass just below the disc of Uranus so slowly that it was almost surreal to behold and mostly visible because my tracking mount stayed on Uranus while the satellite passed by (definitely slower than a low-orbit satellite). I raised the question at CN:

 

https://www.cloudyni...esterday-night/

 

The most likely explanation seemed to be that the object was a spent rocket stage for a geostationary satellite in a very elliptic orbit.


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#3 Jacob.Redshift

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Posted 22 September 2019 - 07:20 AM

Cool!

 

Thanks for the link, too. Interesting read!


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#4 t_image

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Posted 23 September 2019 - 04:36 PM

Hi All,

 

I’ve been staring at the sun again... safely of course!

 

I noticed several satellite transits across the solar disk during my observing.

 

The first was pretty big (probably 40 or more arc seconds) and fast (probably under .5 seconds), and I could definitely see some angular (as in jagged, not as in degrees of size) sort of shape to it. Very cool one.

 

The second one was tiny and slower, round, probably 25 arc seconds in apparent visual size, and a full 1.5 seconds to transit the solar disk.

 

The third was medium to small (35 arc seconds) boxy looking, and also 1.5 seconds to transit.

 

These are all of course my best estimates, as I wasn’t imaging. 

I’m comparing in my mind what I saw today to the three ISS solar transits and one lunar transit that I’ve seen and photographed in the last year, knowing what each of their respective angular diameters and transit times were for those events.

 

It’s always neat to see a satellite through the scope, but what most surprises me is the number I saw in the time that I did. I probably had 25-30 minutes of total time with my eyes actually observing through the eyepiece. 

 

So, that brings the question... what’s your rate of satellites in the eyepiece? —and I mean the unplanned observations of them. 

 

1 every ten minutes seems high, but that’s where I was today.

 

Last night I got one wizzing across the eyepiece while staring at Jupiter. probably had roughly 30 minutes on the eyepiece, so my rate was lower. 

 

I have never kept track, and I wonder how it will average out over time.

 

Anyone have a log where they have some long-term numbers?

 

Just one of those nerdy astronomy questions about which I’d love to hear others’ accounts.

 

As far as the Sun goes,

you are not resolving any transiting satellites.

Most likely their are weather balloons or bugs or something terrestrial.

 

There isn't anything up that that orbiting that will be more than ~2 arc seconds and that will speed slower than 1.5 seconds without being smaller.

You aren't resolving at a level to see a shadow that small.

Only reflections can be see (like a credit card's glint can be seen by search planes a mile away),

but not a small silhouette.

 

Anyone is welcome to prove me wrong.

 

Calsky.com will predict, like with the ISS,

transit of other satellites.

Easier when there are sunspots to get the orientation right (as calsky will tell you the path of transit as well),

but anyone can look up upcoming transits and see if they can see any at the predicted time going the predicted direction.

You're going to need lots of aperture and good zoom and perfect seeing for things that small...

 

The only other transiting orbiter ever photographed was of Tiangong 1, which was up to 20 arc seconds across..

sat transits.jpg


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#5 twjs

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Posted 29 September 2019 - 09:31 AM

I haven't kept track of them, never occurred to me to do so, but this weekend at BFSP I had something cross my FOV quite frequently.


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#6 Jacob.Redshift

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Posted 02 October 2019 - 11:50 AM

As far as the Sun goes,

you are not resolving any transiting satellites.

Most likely their are weather balloons or bugs or something terrestrial.

 

There isn't anything up that that orbiting that will be more than ~2 arc seconds and that will speed slower than 1.5 seconds without being smaller.

You aren't resolving at a level to see a shadow that small.

Only reflections can be see (like a credit card's glint can be seen by search planes a mile away),

but not a small silhouette.

 

Anyone is welcome to prove me wrong.

 

Calsky.com will predict, like with the ISS,

transit of other satellites.

Easier when there are sunspots to get the orientation right (as calsky will tell you the path of transit as well),

but anyone can look up upcoming transits and see if they can see any at the predicted time going the predicted direction.

You're going to need lots of aperture and good zoom and perfect seeing for things that small...

 

The only other transiting orbiter ever photographed was of Tiangong 1, which was up to 20 arc seconds across..

attachicon.gif sat transits.jpg

Interesting. I know I can resolve the space station, but you’re saying nothing else is nearly that large (in apparent angular diameter)?

 

Now I’m more intrigued. Obviously, the glint of reflections off satellites is bright, as you describe, and I have seen them in the fov, but I am definitely resolving shaped objects. So, now is the question “how far away does a bug have to be to be in focus enough for me to see it as a shape across the sun in the fov?” And then, at that distance, how “big” is it in angular diameter?” That might narrow down what kinds of bugs I’m seeing, if that’s what it is. Then, of course, the balloon hypothesis seems more likely in that the focus would be practically the same.

 

Thanks for your insight!

 

On the other side of this, I think we should all have a “personal best” when viewing how many satellite glints we catch in the fov in one night! Just for fun.



#7 t_image

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Posted 04 October 2019 - 04:02 PM

Interesting. I know I can resolve the space station, but you’re saying nothing else is nearly that large (in apparent angular diameter)?

 

Now I’m more intrigued. Obviously, the glint of reflections off satellites is bright, as you describe, and I have seen them in the fov, but I am definitely resolving shaped objects. So, now is the question “how far away does a bug have to be to be in focus enough for me to see it as a shape across the sun in the fov?” And then, at that distance, how “big” is it in angular diameter?” That might narrow down what kinds of bugs I’m seeing, if that’s what it is. Then, of course, the balloon hypothesis seems more likely in that the focus would be practically the same.

 

Thanks for your insight!

 

On the other side of this, I think we should all have a “personal best” when viewing how many satellite glints we catch in the fov in one night! Just for fun.

I'd love to be proven otherwise with resolving smaller satellites transiting the Sun,

I had chased quite a number of smaller object transit predictions (of h-alpha Sun) and captured nothing....

Plus the whole math and physics thing....

Yet Calsky is often spot-on in prediction with lit passes across the Moon. (ie lit sat visible as it approaches Moon against dark sky)....

 

As for "personal best" contest,

here's my first entry:

about 50 of the 60 SpaceX satellites after their launch in July:

https://www.cloudyni...ink-satellites/

SpaceX Starlink satellites
 
There scheduled to launch a second set of these on October 17!

 

And then here are 15 Geosats passing through my image frame:

 

looks like the site removes the source link, have to paste into browser to see high q image:

https://media.giphy.com/media/26gstw642MkcRaIjS/source.gif

Edited by t_image, 04 October 2019 - 04:09 PM.



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