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Hatan
2005-Dec-08, 03:27 AM
Was wondering if it was possible to create a MMT :)

The bigger the mirror is the bigger the price is of course, but the price is actually expodential. So Buying 1 mirror 30" is much more expensive than buying 6 mirror 12" (for the same light gathering)

What would be the constraint of doing so? I just know one MMT (the actual mmt-named one that has been replace by one 6 meter mirror). So I guess you probably need huge amout of computerized motor all over the place to keep everything aligned.

But could it be possible to just align all the mirror to one focus point in the middle and that's it you have your huge telescope for a fraction of the price?

Kaptain K
2005-Dec-08, 06:38 PM
One thing that you may be forgetting is that for a MMT, you are going to need custom ground mirrors. Not only are they off-axis paraboloid sections, but they will need to have the exact same focal length - to a fraction of a millimeter. Such precision is not cheap!

Also, keeping multiple mirrors collimated as the scope tracks the sky would not be trivial.

ngc3314
2005-Dec-12, 07:39 PM
One thing that you may be forgetting is that for a MMT, you are going to need custom ground mirrors. Not only are they off-axis paraboloid sections, but they will need to have the exact same focal length - to a fraction of a millimeter. Such precision is not cheap!

Also, keeping multiple mirrors collimated as the scope tracks the sky would not be trivial.

There are some versions that might work. The classic MMT used leftover mirrors from the USAF MOL program (think reconnaissance satellites operated by astronauts on board), which were standard (paraboloidal?) 1.8-meter mirrors. The MMT used a hexagonal reflective beam combiner to center the focal planes on one point. They were all differently tilted as a result, giving a field of view in good focus for all the mirrors which would be unpleasantly small for most purposes. And, as has been said, they needed to be coaligned early and often.

Another variation was done by the Georgia State people - the MTT or multi-telescope telescope. For spectra of stars, they could get away with putting a bunch of 12-inch mirrors on a single mount and lining up an optical fiber at the focal point of each. For CCD imaging, that would work as long as you don't mindthe cost of a separate CCD at each prime focus, adding the data later (or simultaneously doing three colors, for example). But the cost of the imagers might then dominate the whole project.