35 replies to this topic

[maroubra_boy]

Hello all,

I love doing outreach & sidewalk astronomy. I love getting every type of question from people. I also try very hard to keep our astro techno-jargon out of my presentations, working hard to phrase things in terms that people can relate to & understand.

However, there is one question that still troubles me - "How far can you see with that scope?".

The problem for me is finding a reply that is not patronizing nor too involved so the person doesn't feel like they are being made to look like a moron nor to lose them in an explanation.

In preparing this post, a possible reply could be to say "a scope like this is designed to collect light, really faint light, which allows us to see not so much how far but how faint". Possible?

We all can come up with a flippant X light year reply, but this is a condescending thing to say first up, and certainly dismissive if that is all you says to a genuine question from people who don't know how to relate to an astronomical telescope. There in is the key issue, that people just have no way of relating to our gear that they really only see as "rocket science stuff" in no short way due to education, movies & media hype.

So, how have you answered this perennial question? Was/is your reply shaped by a context? Do you structure your reply to build upon an initial statement? Possibly your reply depends on the individual circumstance?

Alex.

[Dynan]

"All the way to what I'm looking at!"

 

Speaking of questions, when I was in sixth grade (circa 1964) we had a classmate named Ray. He was somewhat challenged, but had a great heart and was a good friend. At an outreach in the school gym, an amateur astronomer was showing his 8" newton. Ray innocently asked, "Can you see Heaven through that?"

 

The was an instant, total, compassionate silence in the gym. (I don't remember the astronomer's answer, but all eyes were on him. I bet many wondered themselves but were too shy to ask.)

[Greyhaven]

Avoiding the math and instrument factors. I have to say we can see farther and farther each and every day...unless its cloudy.

 

Grey

[Taosmath]

I'm not sure that an augmented X light year answer is that bad.

 

How about something along the lines of: 'How far I can see depends on how bright the things are.  I can see some galaxies which are 65 MLy away, but they are REALLY huge and bright.  If things are much smaller & dimmer, then they have to be closer for me to see them. It's like without a telescope,  I can see a flashlight if it's mile away, but I can't see that flashlight if it's 10 miles away.  But I CAN see a car headlight if it's 10 miles away'.

 

Or a match vs a forest fire etc etc. Relating it to the questioner's likely experience is the key.

Edited by Taosmath, 03 September 2023 - 05:44 PM.

[Older Padawan]

I just tell them I don't know. I haven't found that limit yet.

[lwbehney]

Thanks for bringing this up. This question arises frequently from children and adults and is not an absurd, silly, or ignorant question. The question, if answered properly, will give the audience an immediate sense of the capability of your telescope. I would have three answers immediately ready and stored into my memory for rapid access. However, you will now need to acquire additional information, so that you are not considered incurious about the objects you name.

Possible answers:

 

1_  With my telescope used in a dark sky, I can see the Quasar 3C 273, which is 2.4 billion light years distant.  Now you need to be able to define what a Quasar is. Your WO FLT 91 cannot do that, and so it is probably limited to the Virgo cluster of galaxies, but perhaps in your southern hemisphere sky, there is a more distant galaxy within reach of your refractor, which you can name.  

 

2_ A young person in a dark sky with perfect vision can see the Triangulum Galaxy M33, which is 2.73 million light years distant from us. The second most distant galaxy that most of us can see in a less ideal sky would be M31 and is         2.5 million light years distant. If restricted to your latitude in Australia, I don't have a ready answer for you. 

 

3_ Calculate the light gathering power of your lens or mirror compared to the human eye and have that answer ready also. Then calculate the distance our Sun would have to be from Sydney for it to be seen as a 6th magnitude star, and the distance it would have to be from our solar system to be just visible within the limiting magnitude of your telescope. 

 

When I see telescope owners struggle with this common question at outreach events, I just think, how embarrassing it is to introduce this hobby to people and not to be able to answer the most obvious questions.  The audience just feels sorry for you that you are so ignorant of the sky or your gear. If you can answer these questions, you will gain their immediate admiration and respect and they now have in mind a few objects they might one day wish to see for themselves and come away from the experience a little more interested in Astronomy and a realization of how little they know about what lies immediately above their heads. 

[Villa_il_Gioiello]

Well, I guess I’d have to think about is what the farthest object I’ve looked at with my outreach scope (TEC140). If you’ve seen M58, you’re at 62 mly. 

[gwlee]

There’s no need to explain how to build a watch when a person just asks the time.  Without being flippant or condescending, you can simply tell them the approximate distance to the furthest galaxy that you have personally observed with that scope, and be prepared to answer any follow up questions they might have as simply. 

Edited by gwlee, 03 September 2023 - 07:13 PM.

[Migwan]

I haven't done much open outreach.  Just family, friends and an infrequent passer-by or two.   Still, I've been asked that question many times.

 

Not sure it's the best approach, but what works best for me is to go with example.   I tell them how old the light from the current target is.   From there, most come up with the notion of light years on their own and that makes them feel more involved in any discussion that follows.   

[MisterDan]

One might categorize views, as well, such as "If we're talking about landscapes here on Earth, then a big mountain 100 miles away can look pretty cool and impressive in this telescope, if the air is clear and steady.  If conditions are excellent, you may even see trees on that mountain. Sure, you can see that same mountain with your own eyes, but it looks pretty small and vague, with almost no detail. Imagine that - seeing individual trees a hundred miles away!"  People can relate to mountains and trees.  I think an answer relating to terrestrial objects and distances might help.

 

One might then transition to something ala, "A good telescope can see much, much farther, but the objects have to be MUCH, much bigger, too.  The Moon is over 2,000 miles in diameter, and it's 240,000 miles away."

 

Another perspective-bender might be Jupiter:  "Imagine if Jupiter was a shopping bag, and you could pack a bunch of Earths in it, like apples.  That crazy-huge shopping bag could hold almost 1,000 Earths! -And Jupiter is about 600 million miles away!"  (That distance can, of course, be adjusted according to its apparition at the time.)

 

"-And Saturn is even FARTHER - usually more than 800 million miles away!"

 

Kudos, Alex; it's an excellent question. -And kudos for wanting to be able to provide some helpful answers!

 

Best wishes.

Dan

Edited by MisterDan, 03 September 2023 - 06:49 PM.

[maroubra_boy]

I'm not sure that an augmented X light year answer is that bad.

 

How about something along the lines of: 'How far I can see depends on how bright the things are.  I can see some galaxies which are 65 MLy away, but they are REALLY huge and bright.  If things are much smaller & dimmer, then they have to be closer for me to see them. It's like without a telescope,  I can see a flashlight if it's mile away, but I can't see that flashlight if it's 10 miles away.  But I CAN see a car headlight if it's 10 miles away'.

 

Or a match vs a forest fire etc etc. Relating it to the questioner's likely experience is the key.

BINGO!  

 

This is exactly what I was looking for!!!!

 

An analogy that puts it all into perspective for astro laypeople.  Either one can be closer or further away, and then what is the parameter of the scope that allows one or the other or both to be visible.

 

Yes, it is easy enough to state any number of statistics of X billion light years, but numbers are meaningless as the basic concept of what a scope allows us to do is missing if numbers are all one is stating.  BUT, once you first put into context what a scope does, then we can rattle of some stats.  NOW we can show not only how far but also how bright or faint things can be.  With this analogy the Universe becomes MUCH bigger too!  Also brings into context what instruments like Hubble and the JWST are showing us and why being their being outside of the atmosphere is such an advantage.

 

Blooming brilliant, Taosmath!  Thanks!

 

Alex.

[maroubra_boy]

To embellish the analogy, the Sun is the forest fire, stars the match. The larger the scope the fainter the match can be or the further away it can be too.

With binos I can see Neptune, which can be one match, much further away than the Sun but also fainter. Then with a larger scope I can see a very faint quasar which in reality is MUCH brighter than the Sun, a far bigger forest fire, but much, much further away, much further than Neptune. And with the same object, a larger telescope will allow me to see fainter details within it.

I'll polish the analogy some more too.

Alex.

Edited by maroubra_boy, 03 September 2023 - 07:48 PM.

[maroubra_boy]

Well, I was having a play with Sky Safari, scanning through faint galaxies looking at how far away they are when I came across a MONSTER, PGC 4047321.

 

This mag 17 galaxy is right on the limit of what I can see with my 17.5" dob, and I have lined it up as a Hail Mary target.

 

But if a do nab it, this sucker is 11 billion light years away! 

 

Most mag 17 galaxies lie between 400 million and 1.2 billion light years distance.  For this sucker to be 10 time further away and be of the same magnitude of brightness it must be one blooming GIGANTIC galaxy!

 

It is not far from Saturn in Aquarius PGC 4047321.  A little on the low side of altitude, but I'll give it a shot.  It will also require a very dark and very transparent sky to have any chance of catching a glimpse of it.  If I manage to spot it, this galaxy will be one of the most stunning achievements for myself, and something that will blow the minds of anyone who asks me that same question of how far, and I will be able to say "close to the edge of the observable Universe, albeit still 2 billion light years from its edge...

[dave253]

Interesting Alex!

 

 I just had a quick look at SS, the DSS image doesn’t seem to show it, and there’s a brightish (~8) star nearby.

 

The whole ‘how far’ thing is tricky for those folks not used to dealing in light years.

[Dave Mitsky]

You could use the distance scale with one inch equaling one astronomical unit, which means that Proxima Centauri would be 4.2 miles away.  That would give people a handle on how far the nearest nighttime star is.  Then multiply a mile or 1.6 kilometers by the number of light years that the farthest target that has been observed with your telescope lies at.

[maroubra_boy]

I don't start out with saying "light years".  Instead I introduce the topic this way:

 

"Jump in your dad's car (pick your age group) and hit the HyperDrive button - EVERYONE knows what the HyperDrive button does - you go at the speed of light with it, roughly 300,000 km/sec (which pretty much is true thanks to sci-fi flicks).  At this speed it will take you just over 1 second to get to the Moon.  It will take you 8 minutes to get to the Sun.  To get to Mars nearly 8 minutes.  To get to Pluto just over 4 hours.  To get to the closest star after the Sun, Alpha Centauri, 4.3 YEARS.  The centre of the Milky Way, 30,000 years.  Now you have the time scale that light years represents."

 

I usually follow this up by saying:

 

"Now if you look at the fastest man made objects, the Voyager spacecrafts, it would take them over 60,000 years to get to Alpha Centauri!  A distance that takes light 4.3 years to cover."

 

After this people tend to have a much better handle on light years because they can better relate to it and the Voyager analogy makes time and distances of space it even more tangible.

[Jon Isaacs]

It is not far from Saturn in Aquarius PGC 4047321.  A little on the low side of altitude, but I'll give it a shot.  It will also require a very dark and very transparent sky to have any chance of catching a glimpse of it.  If I manage to spot it, this galaxy will be one of the most stunning achievements for myself, and something that will blow the minds of anyone who asks me that same question of how far, and I will be able to say "close to the edge of the observable Universe, albeit still 2 billion light years from its edge...

 

 

According to Sky Safari, the radial velocity is 62.3% of the speed of light.  I suspect the red shift could be an issue observing it visually.  

 

As far as the original question, for me, it's a potential teaching moment. I think most people have heard of a light year but the vastness of a light year is beyond the intuitive comprehension of human mind.  It's a moment where together, we can ponder the immense size of the universe.  

 

Jon

[jgraham]

I once heard that John Dobson would reply to that question with something like “Way ta heck out there!”.

 

I usually reply that it’s not how far, but how faint. I could quote a bunch of numbers, but the distances are so vast that they are beyond our comprehension. Suffice it to say that the Sky is a Very Huge Place there is something to see with every level of skill and every level of equipment, or even no equipment at all. At that point I may point to the moon, planets, and a few bright stars and give their distances in light travel time.

 

I like the “Way ta heck out there!” answer.

[maroubra_boy]

Jonno,

 

Hence the "Hail Mary"...

 

Yes, outreach is about teaching, not just showing.  That was the basis for my starting this thread.  And why I thought this forum could provide me with the solution I was looking for   A lot of kindred spirits here.

 

Outreach is not for everyone - there is another thread running at the moment demonstrating this aspect.  But there are also many people who would like to do outreach but feel shy or intimidated, either because of stage fright or they may feel they don't know enough.  If you feel this way, THIS forum is your lucky charm!  That is why I asked the question that I did here, that there is a wonderful lot of people who have a wealth of experience and knowledge that are only too willing to help.  You just need to ask.

 

Alex.

[mdowns]

I was asked that question (how far can you see?)as a ten year old  when I brought my 4' criterion dynascope to school,as requested by my teacher. The first thing that came to my mind was an ad for that scope or maybe it was the edmund 4.25. The ad said 'read a newspaper headline from a mile away'.To demonstrate, my teacher let me set up the scope outside and with help from some classmates,set up a newspaper 275-300 yards away.Everybody was so very impressed that they could read the headline from that distance,let alone a mile.That simple demonstration had a real 'wow' impact on my classmates and teacher.It seems I got more questions about why was the paper upside down than the original 'how far can you see'.

[Sunsparc]

Well the furthest object I've been able to locate is Andromeda, so I tell them 2.5 million light years.

 

And to further blow their minds, I tell them if a sentient species lived in Andromeda with a telescope powerful enough to see the surface of Earth, they would be witnessing the dawn of man when early humanoid species still lived in caves.

[Captain Quark]

Haven't done outreach, but I'm a big fan of the truth. My chiropractor asks me about astronomy. Part of his job is chatting with the clients to keep them coming back, so he asks me about the stuff I'm interested in so I'll come back and keep paying. He asked me how far I can see. Told him the farthest thing I have seen is 3C273, although what I told him was it was black hole that was eating so much gas that it was some number of trillion times brighter than the sun so that I could see it from 2.4 billion lights years, which lead me to explain that the brightness of an object had more to do with what I can see than how far it is. After I left, it occurred to me a better explanation would have been that the light I saw from it was 2.4 billion years old and that I haven't figured out how far away it is at this moment or how far away it was when it emitted that light.

 

Anyway, the truth, I always try to tell my kids the truth, at least to the best of my ability. I was a teacher for a while and I did the same thing. Just tell people my best understanding of what the truth is about things. Some people can handle that.

Edited by Captain Quark, 24 September 2023 - 12:48 AM.

[maroubra_boy]

Capt,

 

It isn't about not telling the truth or being evasive.  It is about how to explain the truth in a way that makes sense to people who cannot relate to astro jargon.  Without taking this into account, we are inadvertently causing them not to handle the truth by bamboozling them.

 

When they ask "how far you can see" it is because they have no other way to relate to the gear we use.  They don't understand the primary function of a scope is to collect light, not how far you can see like with a spotting scope looking across of valley.

 

There is a quasar I am going to attempt to peg over the next couple of months.  It will take all my experience to nail it as it will be a real Hail Mary effort - magnitude 17.2-ish and 11 billion light years away.  It is actually less of a "how far", more how faint, with the how far just an added bonus.  This quasar also happens to be not too far from Saturn at the moment to give you a general idea of where it lies.  PGC 4047321, aka RX J2125.0-0813, in Aquarius.

 

In preparation for this, I am first going to tease out some magnitude 17+ galaxies in Grus, specifically galaxies in the background of the Grus Quartet.  There is a particular trio of galaxies just south of NGC 7590 that are in a straight line, conveniently lined up brightest to faintest west to east.  If I can spot the faintest of this trio then I know I have a shot at the quasar.  Last month I managed to spot the brightest (mag 16.7) of this trio under a poor transparency sky.  I am encouraged by this effort because the conditions were not great.  So again, it is first about how faint, then if I can manage this then the how far is the added bonus.  For what its worth, I'll be using a 17.5" dob, so I will be pushing my eyes and the scope to everything each can deliver.

[Captain Quark]

...people who cannot relate to astro jargon.  Without taking this into account, we are inadvertently causing them not to handle the truth by bamboozling them...

I guess I'm projecting my own values into the situation. I would rather be exposed to the best possible explanation, even if it bamboozles me, than not. Then I'm free to investigate further, or not.

 

...It is actually less of a "how far", more how faint, with the how far just an added bonus...

Yes, so it has to do more with how bright something is than how far it is, and next time my chiropractor asks, that's the first thing I'll try to remember to say. And "far" not only means distance in space but also time.

[csrlice12]

I see the past....you see, it's not just a magnifier, it's a time machine.....