The Very Best Telescope

Discover Magazine ^ | dec 7, 2002 | William Speed Weed

[The Raven]

...CHARA can detect individual planets around binary stars

Wow!!!

[The Raven]

Here's a picture as well....

Top: Together, CHARA's six telescopes compose a light-gathering instrument with a maximum aperture, or baseline, equal to the farthest distance between two scopes: 1,080 feet. The Y configuration allows astronomers to vary the aperture for different observations. Bottom: For an interferometer to work, starlight gathered by separate telescopes must hit a detector at the same time. To compensate for the extra distance light travels to telescope 2, light collected by telescope 1 is diverted precisely the same distance on a delay line. Graphics by Matt Zang

[Conan the Librarian]

Dang and I thought my 10" Meade was the best. :(

[Conan the Librarian]

Dang and I thought my 10" Meade was the best. :(

[IronJack]

I'm no electrical engineer, but I would think an AND logic gate would overcome the synchronization problem. For a given signal, a threshold voltage would have to be overcome to drive the gate high, and the same voltage would have to come from every one of the sources. Until it did, no signal would pass.

But then, I'm sure better minds than mine have considered that idea.

[FrogMom]

FrogDad and I spent about 4 hours out with our 10" Meade last night. It was cold but there was glorious viewing!

[Prodigal Son]

I don't want to sound too ignorant about astronomy- but what exactly can you see with a good 10 inch? Are we talking galaxies? Rings of Saturn? Jupiter's red spot? Be specific if you don't mind- I'm really interested. What would be the range of what you could see?

[Dan(9698)]

>>...what exactly can you see with a good 10 inch?

Ten inch and smaller objects? :)

[boris]

Paragraphs are our friends.

[longshadow]

but what exactly can you see with a good 10 inch? Are we talking galaxies? Rings of Saturn? Jupiter's red spot?

All of the above. And nebulae, globular and open star clusters, binary stars, and much more. Easily. Even a smaller scope will allow you to see anything on your list.

The larger the (conventional) telescope, the fainter the object you can see, as well as finer detail.

[longshadow]

Holy Grail of optical astronomy ping!

Optical interferometry is the way to go....

[The Raven]

Yep...the paragraph breaks didn't make it....But if you click the link for better reading there are more pictures

[longshadow]

What would be the range of what you could see?

There is no "range" limit, per se.

The limiting factor is how faint the object is. Light gathering ability of a conventional telescope is determined by the area of the primary lens or mirror. The light collecting area is a function of the square of the diameter of the lens or mirror, so a an 8" scope will collect 4 times as much light as a 4" scope, and so on.

Planets are so bright that a very modest telescope is adequate to see them. 2" - 3" refractors will do the job, though they won't show a great deal of detail. The ubiquitous 8" catadioptric scopes (Meade, Celestron) will show much more detail on planets, plus have the light gathering ability needed to see faint, diffuse objects like nebulae and galaxies.

Trivia question: name four galaxies visible from Earth with the naked eye ....

[general_re]

Trivia question: name four galaxies visible from Earth with the naked eye ....

M31, both Magellanic clouds...and our own galaxy, of course ;)

[Prodigal Son]

Name four galaxies...

Hmmm. I would start with our own Milky Way. Even though we can't see it as a whole we do see a lot of it. I think I've heard Andromeda is a popular target for star gazers as well and I'll guess that it's visible as well to the naked eye. From reading a small book on astronomy while I was living in South Africa (I wanted to understand the unusual sky I was looking at in the Southern Hemisphere) I see to recall something about the Large Magellanic Cloud but can't recall if this is one galaxy or many that you can see there. I don't know if that counts as an answer or not. Other than that, I'm stumped.

But coming back to the question about what you can see. When I say galaxies- I don't mean a bright spot that looks like a star. As far as that goes- that's what planets look like to the naked eye. I want to know, can you see the galaxy's spiral shape? Can you see the way the stars clump in the middle and then others are flung out on their rotational axis. How much detail of a galaxy could you see?

Every time I ask a telescope enthusiast on the net these questions- they always answer back with the mathematics of the lens and whatever. I just want the bottom line. If I look at a galaxy with a ten incher- does it look like a galaxy? If I photoed Andromeda through a 10 inch telescope would I have a picture that looked like a galaxy or a big fuzzy star?

On the planets again- would a ten inch telescope allow you to see one of Jupiter's moons as it moved across the planet?

Don't get too technical. I don't care that much about the mechanics of the scope- I just want to know what I can see in the cross hairs ;-)

[Focault's Pendulum]

Paragraphs are our friends.

This keeps up...I'm gonna need a prescription for glasses. My eyes were perfect till I started Freepin'.

[longshadow]

M31, both Magellanic clouds...and our own galaxy, of course ;)

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[longshadow]

Name four galaxies...

You got it...... well done.

But coming back to the question about what you can see. When I say galaxies- I don't mean a bright spot that looks like a star. As far as that goes- that's what planets look like to the naked eye. I want to know, can you see the galaxy's spiral shape? Can you see the way the stars clump in the middle and then others are flung out on their rotational axis. How much detail of a galaxy could you see?

Depends on the size/distance of the galaxy... as you already know Andromeda is visible with the naked eye, and is about the size of a full moon. In a scope, you can see the bright central core and some spiral structure. What you won't see is individual stars; that requires a really big scope. So, even with a modest amateur scope, you can see galactic structure in nearby galaxies...

If I look at a galaxy with a ten incher- does it look like a galaxy?

Andromeda, or some other nearby spiral galaxy, yes.

If I photoed Andromeda through a 10 inch telescope would I have a picture that looked like a galaxy or a big fuzzy star?

Assuming you did everything right (which isn't easy), the picture would show fainter detail than you would see looking thru the scope with your eye, but no finer. (IOW, the photgraphic emulsion, or a solid state CCD detector, is more sensitive to light than your eye if you take a time exposure and integrate all the photons hitting the scope during the exposure. The eye is snap-shot; it doesn't integrate over time)

On the planets again- would a ten inch telescope allow you to see one of Jupiter's moons as it moved across the planet?

Overkill. First, people with really good eyes can just barely see the Galilean moons with the naked eye. Any scope, even a cheap 2" refrator, heck, binoculars, will allow you to see them when they're next to the Jupiter. Something a little bigger might be needed to see them (actually, you'll see their SHADOW) crossing in front of the planet, but 10" is MORE than enough; I know an 8" will do it, and I'd bet something much smaller would work.)

Don't get too technical. I don't care that much about the mechanics of the scope- I just want to know what I can see in the cross hairs ;-)

10-4. No quiz. Hope this helps.

BTW, if your thinking of buying a scope, you haven't asked the MOST important question: How hard is it to set up/take down?

The bigger the scope, the more work and hassle it is to lug it to your viewing site, set it up, etc.

The most important rule of amateur astronomy is that is doesn't matter how BIG your scope is if it just sits in the garage collecting dust, because it's too damned much work to drag it out.

It is for this reason that the best first instrument is a pair of good 7x50 binoculars.... or a compact, lightweight modest telescope. If you get hooked using that, then move up to a bigger scope.

Better to spend a few hundred $ and find out your interest is short-lived than to spend ten times that....

[Mulder]

....if you take a time exposure....

Is this difficult to set up if you have the right scope (one that moves automatically to adjust for the earth's rotation)? How much does it cost (ballpark) to do it right?

[VadeRetro]

"Eventually, those lessons will come back home, telling us what our sun was like in the past and exposing threats we can expect from it—giant flares, perhaps, or periods of dimming that could trigger an ice age.

Lovely! So in theory we could be toast in the next half hour. Except it hasn't happened so far since the formation of life on Earth.