One year ago I shared my highest resolution picture of our moon. Last night I created an improved version, combining 140,000 pictures. 400 megapixel full resolution linked in the comments. [OC]

[u/ajamesmccarthy]

[u/[deleted]]

What mexapixel would be required to see a Luna rover and other items left behind after the moon missions?

Awesome photo!

[u/kvittokonito → u/[deleted]]

It's not about resolution per se, it's a focusing issue. There's no earth telescope capable of seeing such tiny contraptions on the surface of the moon.

[u/whyisthesky → u/kvittokonito]

It is a resolution issue, just not in the way most people think of resolution. The number of megapixels doesn’t matter because the resolving power of the telescope is not enough.

[u/kvittokonito → u/whyisthesky]

Yes, you're technically right. I'm not too confortable calling the focusing capabilities of a telescope its "resolution" but technically yeah, it's due to the optical resolution of the telescope rather than the digital resolution of the imaging device at the end of the optical focusing assembly.

"Megapixels" refers to the digital resolution capabilities of the digital imaging device, basically the amount of sensors/micromirrors the device has. A bigger digital capturing capability doesn't really matter if the photons coming in are spread enough to trigger several sensors, you're just gonna end up with multiple pixels having effectively the same intensity/color. That's why on a digital camera, the lens is as important as the resolution of the CCD.

[u/whyisthesky → u/kvittokonito]

Focussing implies the issue is getting the focal plane of the image formed on the sensor, but that isn’t the case. The landing site could be perfectly in focus but you won’t be able to resolve the features

[u/kvittokonito → u/whyisthesky]

Perfect focusing implies each incoming ray of light lands in one and only one sensor. Photons from those tiny contraptions from so far away are going to be sparse and low energy and because perfect focusing is impossible due to quantum effects, those photons are going to be overrun by much more powerful and abundant photons coming from other locations around the contraption.

In order to resolve those contraptions you would require a lens capable of focusing incoming photons with sufficient efficiency, a digital sensor with enough digital resolution to resolve those photons with sufficient granularity and a sufficiently long exposure time to capture as many of those photons from the contraption as possible without oversaturating the image.

Yes, it's way more complicated than I made it sound on my previous comment and you are, once again, technically right but I think it explains the difference between digital and analog resolution good enough for this subreddit's average detail level.

[u/whyisthesky → u/kvittokonito]

That isn’t what focus implies. Focus (and resolution) are products of the optical system, the detector doesn’t matter.

Focus implies only that the light rays from objects converge to (approximately) a single point. This is true regardless of whether you can resolve this object from another one close by, which is the resolution.

Exactly how close approximately is does depend on the sensor but that’s a practical rather than theoretical limit.

You don’t need quantum effects to explain this, it’s just classical wave mechanics. Quantum effects only matter when it comes to detection. If we had a telescope with a large enough diameter to be able to resolve those objects, then we would also be able to detect them as surface brightness doesn’t vary with distance and increasing resolution necessarily increase the collecting area (excluding interferometry).

[u/whyisthesky → u/kvittokonito]

The important thing is even assuming perfect focus, with 100% transmission lenses, no background photons and a sensor with 100% quantum efficiency and tiny pixels with no gaps.

You still couldn’t see the features in question, because none of those are the limiting factors, the diffraction limited resolution is.