Could a lens or mirror be placed in orbit on the same flight path with other parts to make a telescope or on the horizon of the moon to see farther with the Hubble?

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    $\begingroup$ I don't think you understand what "amplified" could mean. The light-collecting ability is limited by the size of the first element. The resolution depends on any number of factors. $\endgroup$ Commented Jul 24, 2018 at 14:20
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    $\begingroup$ Orbital telescopes are using mirrors and not lenses. Lenses have various disadvantages: 1) they are weighty 2) their focus for red and blue colors is a little bit different. Professional, HQ telescopes are using practically always mirrors. $\endgroup$
    – peterh
    Commented Jul 24, 2018 at 20:26

2 Answers 2


Speaking in general, telescopes are designed as complete systems from the beginning. It's not generally feasible to improve performance by just adding yet another lens or mirror to the assembly. The reasons for this are not simple to explain, since this is basically the whole theory of instrument design.

Usually you start with a set of requirements (limiting magnitude, angular resolution, linear resolution in prime focus, etc) and with a set of constraints (cost, size, weight, materials).

You settle on a given architecture (newtonian reflector, Ritchey-Chrétien, doublet / triplet / quadruplet refractor, etc), and then start to work out the main parameters: aperture, focal length, etc.

There's an iterative process involving computer aided design to work out the details of each optical element; at each step you need to solve problems such as eliminating internal reflections, etc.

In the end, what you have is the design of the whole optical stack: say a Dall-Kirkham reflector, 1 meter aperture, f/8, with mirrors of whatever radiuses of curvature, etc.

Once that's set in stone, it's hard to change in a major way. Minor upgrades might be possible (add a corrector lens, or a different secondary mirror), but not huge modifications.

TLDR: No. Start with a bigger instrument from scratch if that's what you want.


Far from "orbit" some of the longest telescopes in history are:

Hevelius' Telescope

Huygen's Telescope

Apparently Adrian Auzout and others made telescopes of from 300 to 600 ft (90 to 180 m) focal length, but I've not found a drawing from the late 1600's of it.

In theory you could have a distant objective lens but either it would need to be huge (costly) or your field of view would need to be extremely narrow (only useful for extremely distant objects). Then there's the cost of stabilizing the lens and maintaining alignment.


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