The Quadfractor

[Naemeth]

I was thinking, could you theoretically make a quadfractor?

By that I mean get 4 small refractors (say 80mm F/5 objectives) and through various diagonals get them to reach one focal point at ~400mm and have a focuser there? Thereby having an almost 320mm objective.

Could it work?

[David Smith]

I believe this is possible. The problem with optical interferometers is the extremely narrow tolerances required to form an acceptable image.

[nmoushon]

Check out the LBT (Large Binocular Telescope). As David said its very much possible but very very very hard to get all those light paths to align to the exact same spot. Refractors would be the "easiest" as no need to collimation like the LBT has since its a reflector, which creates an even bigger problem. The people at the LBT are still trying to find a better way to deal with it...coupled with the adaptive optics it has also.

I believe the equipment required would be way too expensive for 99% of us ametuers.

[chiltonstar]

4 80mm fracs would make the equivalent of a 160mm frac wouldn't it?

Chris

[laser_jock99]

.....it would simpler/cheaper just to get the bigger scope! What some people do though is have 4 identical scopes imagaging (4 different wavelengths) at the same time.

[Peter Drew]

If you could successfully combine the images you would certainly produce a brighter one, but as the objectives are individual I think you would retain only the resolution of a single 80mm albeit perhaps improved by the "stacking". 

[cassiewoofer]

I'm sure that resolution is directly related to aperture.... or baseline separation..... isn't that how these arrays (as in the very large)work?

[cassiewoofer]

Ooops, no post edit....  so the distance between the two (or four) telescopes would determine the resolution.

[nmoushon]

If you could successfully combine the images you would certainly produce a brighter one, but as the objectives are individual I think you would retain only the resolution of a single 80mm albeit perhaps improved by the "stacking". 

This isn't true. The resloution is determined by the spacing between the scopes. You then measure the distance from center to center and that is the resolution of your combined scope. So if two 80mm where 20mm apart you would get a resolution of a single 100mm scope. Not sure how you would calcuate when you combine 4 though. It also speeds up your imaging. So two 80mm scopes at f/6 now essentially becomes a 100mm scope at f/3....I think. Could be wrong on that one but to what I understand thats how it works.