How can we see the ISS at 200 miles away with the naked eye?

[DaveC426913]

Why? Scratch a hole in the mirror, so you can look through at your outstretched arm thumb. Point your thumb at the target, then reflect the Sun onto your thumb. Problem solved.

Anorlunda's rescue mirror is solid metal - for durability.

Otherwise though, it's a clever idea for sighting.

However, it does not obviate the need to wobble the mirror.

 

[Baluncore]

However, it does not obviate the need to wobble the mirror.

If you want to send morse CW you will need more reliable dots and dashes than wobble. I think you are assuming high contrast green grass background, not snow, or the glint of wind on small lakes.

The lights on Boeing aircraft flash once, Airbus flash twice, which better confirms their position in your vision.

If there is no hole in the mirror, use the edge of your thumb and the edge of the mirror. Practice aiming at a nearby object before you need it.

 

[DaveC426913]

If you want to send morse CW you will need more reliable dots and dashes than wobble. I think you are assuming high contrast green grass background, not snow, or the glint of wind on small lakes.

I'm not sure where morse code or background contrast factors in. I am simply assuming virtually any situation where the intended target doesn't know ahead of time exactly where to look - and all we're trying to do is get their attention, not send a (more complex) message. For example: the provided video.

A flashing point of light will be orders of magnitude more catching to the eye than a steady dot, which could easily be overlooked in almost any real world scenario (plausibly including the provided video).

 

[Baluncore]

A flashing point of light will be orders of magnitude more catching to the eye than a steady dot, which could easily be overlooked in almost any real world scenario (plausibly including the provided video).

I believe the point of light should turn on and off in a steady and controlled manner, not randomly flash or flicker.

 

[DaveC426913]

I believe the point of light should turn on and off in a steady and controlled manner, not randomly flash or flicker.

I am more confused now. This is the arc of the pertinent conversation, as I see it:

Post 24:

Yes of course. But you still have to wobble your rescue mirror!

Post 25:

Why? Scratch a hole in the mirror, so you can look through at your outstretched arm thumb. Point your thumb at the target, then reflect the Sun onto your thumb. Problem solved.

Anorlunda's rescue mirror is solid metal - for durability. Otherwise though, it's a clever idea for sighting.

However, it does not obviate the need to wobble the mirror.

Oh I think I see. Are we talking past each other?

Are you associating "wobbling the mirror" with the mirror-holder and his attempt to place the reflection on the target. (which is why your solution concentrated on accurately aiming the mirror)?My understanding is that the mirror-wobbling is to make the target see the flashing - which is far more noticeable than a steady light. For that, the holder needs to manually flash the target on and off.So, now:

I believe the point of light should turn on and off in a steady and controlled manner, not randomly flash or flicker.

Other than wobbling it back and forth - how might one do that with an inert hand-held mirror?

 

[berkeman]

Other than wobbling it back and forth - how might one do that with an inert hand-held mirror?

Cover it with your hand, for example. But I think it's much more common to flash by tilting.

BTW, I hope everybody knows how to flash "S-O-S" in Morse code. If you don't know any other Morse Code symbols, you at least need to know "S" and "O", IMO...

 

[TruthSeeker777]

I think we've established that the visibility of stars pretty much resolve any doubt.

Visibility yes but not distance. I'd be weary of using distance of objects so far away that we can't really verify empirically.

 

[malawi_glenn]

Visibility yes but not distance

How far is it to Vega?

 

[TruthSeeker777]

Note again that the dynamic range of our eyes is very wide. A camera taking a photo of a brightly lit astronaut won't capture the dim stars.

what about pictures of the full moon and stars?

 

[DaveC426913]

Cover it with your hand, for example. But I think it's much more common to flash by tilting.

Good point.

BTW, I hope everybody knows how to flash "S-O-S" in Morse code. If you don't know any other Morse Code symbols, you at least need to know "S" and "O", IMO...

Other very good distress signals (without being exhaustive) to keep in your mind's back pocket:
- upside-down sail, flag or burgee
- three of anything: three shots, three whistle blasts, three flashes of a light mirror, three fires
- more primitively: three stacked logs, three arranged rocks, three of anything you can get your hands on.

 

[DaveC426913]

what about pictures of the full moon and stars?

A camera can be set however it suits the photographer. To capture stars, the full moon will likely be blown out, but you can get them both in the same shot. The nuances of what you want and what you get might best be left to a new thread.

 

[DaveC426913]

How far is it to Vega?

Google is your friend. (Or was that a rhetorical question?)

 

[malawi_glenn]

Google is your friend. (Or was that a rhetorical question?)

The truthseeker disqualified stars as objects here because we do not know that they are distant. So I want to know how far it is to Vega from here.

(Vega is my second fav star, after Helios)

 

[DaveC426913]

Visibility yes but not distance. I'd be weary of using distance of objects so far away that we can't really verify empirically.

What makes you think we can't verify their distances empirically?

The parallax method can tell us the distances to nearby stars with nothing more than the geometry of Earth's orbit and six months of waiting time.

 

[DaveC426913]

The truthseeker disqualified stars as objects here because we do not know that they are distant. So I want to know how far it is to Vega from here.

Then Google is your friend.

 

[malawi_glenn]

Then Google is your friend.

I rather let truthseeker reply. For the reasons I gave.

 

[DaveC426913]

A quick check suggests parallax methods can work adequately out to as far as 100 to 300 light years. That covers hundreds of thousands of local stars.

 

[Baluncore]

Other than wobbling it back and forth - how might one do that with an inert hand-held mirror?

I see a wobble as an unsteady angular variation.

Cover it with your hand, for example. But I think it's much more common to flash by tilting.

I would momentarily hide the target behind my outstretched hand. That way, I have quick and accurate control of the target illumination, without moving the mirror.

 

[malawi_glenn]

A quick check suggests parallax methods can work adequately out to as far as 100 to 300 light years. That covers hundreds of thousands of local stars.

Gaia can reach further

 

[DaveC426913]

Gaia can reach further

Are Gaia's findings an empirical source of observation? I mean are its results measured using parallax (geometry)? Or do its results rely on our understanding of astrophysics?

The OP wanted to trust direct empirical observation.

Update:
"These measurements will help determine the astrometric parameters of stars: two corresponding to the angular position of a given star on the sky, two for the derivatives of the star's position over time (motion) and lastly, the star's parallax from which distance can be calculated."
https://en.wikipedia.org/wiki/Gaia_( spacecraft )#Measurement_principles

Well, apparently they are.

 

[russ_watters]

what about pictures of the full moon and stars?

Generally they are composites. You can't easily do both with one shot.

 

[DaveC426913]

Generally they are composites. You can't do both with one shot.

To be pedantic, you can. The OP did not seem to be too concerned about the aesthetics of the result (i.e. a blown out Moon is still serviceably visible for his purposes).

 

[malawi_glenn]

Is Gaia an empirical source of observation?

The OP wanted to trust direct observation (presumably as opposed to derivation based on various theories that are still being tweaked.)

It measures parallax and motion of stars.

If you just want to use your senses, you can not do parallax accurately up to 300 lightyears.

 

[russ_watters]

To be pedantic, you can. The OP did not seem to be too concerned about the aesthetics of the result (i.e. a blown out Moon is still quite visible).

Sigh, fine. I added a qualifier.

 

[TruthSeeker777]

What makes you think we can't verify their distances empirically?

The parallax method can tell us the distances to nearby stars with nothing more than the geometry of Earth's orbit and six months of waiting time.

It depends on what relative distances you set for the objects around what you are trying to triangulate? It assumes you know the distance to an object X and you measure the angular drift in reference to that object Y compared to the other you know about X ? So what is the reference object ?

 

[DaveC426913]

If you just want to use your senses, you can not do parallax accurately up to 300 lightyears.

Sure, that's not the point.

The OP wants to rely on empirical evidence. By that I presume he means "don't rely on our theories of stellar distance calculation".

Telescopes provide the requested empirical observation. We see the parallax.

 

[malawi_glenn]

By that I presume he means "don't rely on our theories of stellar distance calculation".

Google is your friend here.

Two of my teachers in astrophysics were (are) involved in the Gaia-project.

 

[malawi_glenn]

It depends on what relative distances you set for the objects around what you are trying to triangulate? It assumes you know the distance to an object X and you measure the angular drift in reference to that object Y compared to the other you know about X ? So what is the reference object ?

You want a crash course in parallax method?

 

[DaveC426913]

Google is your friend here.

Two of my teachers in astrophysics were (are) involved in the Gaia-project.

So what? The OP doesn't want to rely on astrophysical theory. We can accommodate that by simply using telescope observation. What is there to Google? (That is a rhetorical question.)

 

[malawi_glenn]

So what?

If you want to know how Gaia works, you can google it.