# Array of telescopes with single orbiting collector?

Might such a thing give better images than we could get from other virtual telescopes with multiple collectors? Or is having multiple collectors not a limiting factor? Could a single collector compensate for atmospheric distortion in a way multiple collectors cannot?

We sometimes use arrays of radio telescopes spread over a wide distance to increase the effective aperture. I think that array is called a virtual telescope, but I might be wrong. A normal radio telescope has a collector in the same way that a satellite dish has a collector. The reflector of a radio telescope is parabolic so as to focus parallel waves to a single point. That works because dish and collector are in a fixed geometry. The reflectors of my imagined telescope would need to turn so that they reflected waves from whichever part of the sky was being observed onto the collector. That turning would change the required curvature for perfect parabolic-ness.

The telescope I'm imaging would have a (perhaps geostationary) satellite as the collector and an array of flat-ish reflectors spread over hundreds of kilometers working together to collect waves from the same part of the sky. Being non-parabolic, the reflectors wouldn't be very efficient, but they could compensate by being numerous.

The collector wouldn't have to be geostationary, because the reflectors already need to compensate for the earth turning; adding the satellite's movement into the equation wouldn't be terribly complicated.

• Hi there, welcome. I'm not really sure what you're talking about. What do you mean by virtual? We have remote telescopes that can be accessed online. There are people building space telescopes that can be accessed by consumers (non-scientists) remotely. What do you mean by collector? What would a non-parabolic reflector be? I just can't grasp what you imagine here. – Alphecca Oct 12 '18 at 23:35
• Hi! We sometimes use arrays of radio telescopes spread over a wide distance to increase the effective aperture. I thinks that array is called a virtual telescope, but I might be wrong. A normal radio telescope has a collector in the same way that a satellite dish has a collector. The reflector of a radio telescope is parabolic so as to focus parallel waves to a single point. That works because dish and collector are in a fixed geometry. The reflectors of my imagined telescope would need to turn so that they reflected waves from whichever part of the sky was being observed onto the collector – OutstandingBill Oct 13 '18 at 3:17
• Well, in my experience "virtual" does not refer to a radio telescope array, but I understand what you're thinking of now. Can you post a diagram to make it crystal clear? – Alphecca Oct 13 '18 at 16:47
• Someone has voted to close this question as POB: "... answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise." I've voted to leave it open, as this is the wrong reason to close: I'm confident the question has the capacity to elicit authoritative answers. It's poorly worded so it potentially qualifies for "unclear what you're asking", but the OP's comment helps clarify it. Questions should only be closed when they don't meet the site's standards; otherwise, low-quality posts can be edited or simply downvoted. – Chappo Hasn't Forgotten Monica Oct 13 '18 at 23:00
• @Alphecca, good idea - it's pretty crude, but I hope it gives the gist. – OutstandingBill Oct 14 '18 at 8:38

The other way to combine multiple telescopes, which is along the lines of what you are thinking, is to phase the two telescopes, meaning that not only are you laying the images on top of each other, you are also doing it so that the two images have the same phase, meaning they have traveled exactly the same distance from source to collector. What you gain by doing this is that the resolution you get this way is what you would get if you had a telescope aperture that circumscribed the two telescopes. For instance, if you had two 10 cm telescopes separated by 10 meters, you'd end up with an image that had a resolution of a 10 meter diameter telescope; however it would only have the light collection capability of the two individual telescopes, so though you have the resolution of a 10 meter telescope, you have the light collection capability that is only $$\frac{2*{0.05}^2}{5^2} = 0.02\%$$, meaning that you'd need to take an exposure of 5000 seconds to get the same signal you'd get with a 1-second exposure with a 10 meter telescope.
• To get an idea for the infrastructure you need, check out the LINC-NIRVANA setup for the Large Binocular Telescope. The math like all imaging math, basically comes down to differences in pathlength, known as Optical Path Difference (OPD). You talk about optical quality based upon its average OPD, so a $\lambda$/10 lens is a pretty good one because it adds disturbances in the wavefront that are only a 10th of a wavelength. – Dave Oct 16 '18 at 21:15