Bringing Mars Closer Than The Moon

[astrosite]

Hi, I'll plan to get fancier (HTML, etc., later). Right now, BTW, I can only logon to space.com from public library computers; my home computer never comes back if I try to register as a user here.<br /><br />Anyway, to my main point:<br /><br />The first time I saw the Moon through a REAL amateur telescope, an eight-incher, I was totally blown away! It was like being on Apollo 8, cruising over the Moon's surface, or at least on approach to the Moon.<br /><br />Sometime later, I asked a knowledgable amateur astronomer and friend about what size of scope it would take to see Mars like that. His initial answer was off due to him having to do an improptu calculation in his head. But he gave the right idea: mulitply the aperture of an 8" by how much further away Mars is than the Moon.<br /><br />I've been thinking about that ever since. The scope would have to be hundreds of feet in diameter. But since then, I've also learned about interferometry. You can effectively have the aperture of a huge scope by just having two (regular) mirrors that far apart. The trick is, you have to get up an interference pattern, indicating that both mirrors are aimed at the exact same point in the sky at the exact same time. Other problems include atmospheric turbulelence and the dimness of the image (a filled aperture would give an appropriately bright image, of course). Then you have to use computers to analyze the interference patterns, assuming you can even acquire these patterns as desired. Professional astronomy uses interferometry and active/adaptive optics to counter the effects of the atmosphere and the imaging system's local environment (heat, moisture, vibration, etc.).<br /><br />But this interferometry is very hard, even for professional astronomers. Nevertheless, I think that interferometry, adaptive/active optics, and other necessary techniques can be brought to amateur astronomy. You know how at star parties, amateurs are standing around and using and talking about their twelve inch

 

[wisefool]

Your idea, whatever it turns out to be, is inspired. However, even if you do bring interferometry to amateurs, and in some ways it already is available, you will not be able to "bring Mars closer than the moon."<br /><br />Go back to the idea of a chain being no stronger than its weakest link. EVEN IF you could produce something here on Earth that would have the power to magnify Mars to something larger than the moon, you would not see Mars any better than how we now see it. Why?<br /><br />The weakest link is the atmosphere through which we view. Put simply, only on the best of nights can we amateurs use more than 300 power without ALSO magnifying the perturbations in the atmosphere to turn the image into mush. <br /><br />Mars is an especially difficult target, because it has subtle surface details, and is very small. When we look at Mars we are looking at "the full moon," and you already know how poor the features other than mare show during the full moon when there are no shadows to accent craters and mountains.<br />

 

[alkalin]

Yes, but what if you could combine a large synthetic aperture and AO with interferometery????<br /><br />Some things to look forward to.

 

[wisefool]

The Keck scopes, and even the binocular scope going up in Arizona, will still not be able to equal a good 8" scope on the Moon when viewing Mars, for several reasons. Let's start with the fact that Mars has an atmosphere, and our moon not. Let's continue with the fact that Mars is rarely close, and then not for long. Right now it is hardly larger than Uranus.<br /><br />The really big problem is that AO (adaptive optics) does not yet work in visible light, because of the narrow wave lengths we utilize to see. AO works with infrared, because the longer wave lengths can be manipulated by mirors and computers in real time. Therefore, AO is at best a partial solution to the Earth's atmosphere effects -- and AO is way beyond amature budgets.

 

[astrosite]

Howdy! Thanks for your responses!<br /><br />Due to time limitations at the moment, I'm going to risk answering/responding off the top of my head. I may have to correct myself later, or be corrected.<br /><br />Wisefool is correct about the atmosphere turbulence problem. But Alkalin hints at the solution by mentioning AO. Wisefool, I think AO works in visible light but that infrared is better. Atmospheric turbulence less affects infrared. But AO, originally developed in the 1980s for the "Star Wars" program, includes shooting lasers high into the atmosphere to excite certain atoms and generate light bursts at high altitude. This technique creates artificial guide stars near the actual sky object being observed. Less fancy is just to use the light from the object being obsereved or from a nearby object, to detect the warping of the wavefront. This can be a problem for faint objects. Whether a laser is involved or just natural light, the deforming of the wavefront has to be detected. Then a deformable secondary mirror in the telescope counteracts this. <br /><br />stevehw33: I think you're thinking the way I first thought. I knew that if you roughly consider the area of a mirror to be the same as if it were flat, then it's a matter of A = pi times radius squared (area of a circle). So if Mars were a thousand times further than the Moon (it's usually well LESS further away than that), you would need merely 1,000 times the light gathering power of an 8". That's way less than the area of a scope 1,000 times wider (8,000").<br /><br />But my amateur friend who told me that you need to multiply the aperture turned out to be right, after I did enough investigating. Aperture is everything; if it's a thousand times further away, you need 1,000 times the APERTURE, not 1,000 times the area. It was a sinking feeling. But then interferometry comes along and saves the day.<br /><br />The reason aperture is needed is because of the way light from distant objects is "convolved" by the time it

 

[astrosite]

Oh, I forgot to mention, I believe that my new technique, while not EASY, is easiER than interferometry.