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Dragonfly: An optical telescope built from an array of off-the-shelf Canon lens

dunlap.utoronto.ca

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Re: Dragonfly: An optical telescope built from an array of off-the-shelf Canon lens

#71

Post by ggm »

Lovely project. When comparing images from this and other scopes, remember that almost all Astrophotography nowadays has moved on from exposure from a single light pipe into a negative, and development onto a photo: They are constructs from grids of sensors, with differing receptance across the RF spectrum (visible and non-visible) subject to intense signal processing, and false colour projections.

About the only point you can discuss as a comparator is the angular resolution and even that means asking how much has been interpolated.

I love modern astro images but I am unsure we even should call them "photography" because they're "painted", by the astronomer or their appointed colour artist.

"this one has more IR boost, but I added a hint of green for dramatic effect"

Also to the angular resolution thing, we're often also looking at what is projected into our mind as a 2D structure. The horse head nebula is a 3D state of matter. It wouldn't look like JFK's head from our angle, but might well from another point of view, or a melon, or like.. nothing at all.

Most "constellations" are not physically interconnected in any sense, and are not a group the way a galaxy or star+planets are, and need not lie the same distance away from us. They're the view of these objects on an imaginary surface painted by the astrologers.

https://en.wikipedia.org/wiki/Flammarion_engraving

Re: Dragonfly: An optical telescope built from an array of off-the-shelf Canon lens

#72

Post by woopsn »

lvspiff wrote: post #27
shiftpgdn wrote: post #16

Can someone smarter than me explain why astronmers can't stick something like this on the back of an existing geostationary platform (like what is used for the XM radio sattelites) and get amazing data out of them? Surely sticking something like this array 100km into space will yield better results without the overhead of a 20 year mission plan like James Webb or Hubble.

I've always wondered that myself - If the Russians could build and launch sputnik in 1957 and get it around the earth a few times why aren't we seeing a huge number of backyard dad+son duos building rockets to launch their own telescope array. Its amazing that its a 60 year old feat that is still only in the hands of governments and massive corps

You might look up the sagas of Rocket Lab and other small launch providers if you're interested in what it takes to put ~200lb into LEO today. It's way beyond dad and son stuff, still incredibly hard, but not so much anymore that you need to be Boeing/Lockheed/SpaceX/etc if not a national agency. This is a recent achievement.

Re: Dragonfly: An optical telescope built from an array of off-the-shelf Canon lens

#73

Post by nl »

Aspos wrote: post #43
antognini wrote: post #11

This kind of a setup of a large number of small, cheap detectors works well for observing diffuse objects with low surface brightness. Generally speaking telescopes improve with size because larger telescopes can resolve smaller objects, so you can concentrate the light from your source into a smaller patch and increase the signal-to-noise with respect to the background. But once you have resolved the object (which d…

Can one use millions of smaller detectors if one finds a way to point them in one direction and synchronize them to take pictures at the same exact moment? I mean, can millions of phone cameras make one giant virtual telescope?

Broadly, yes.

The key term you are looking for is "exposure stacking". See for example https://markus-enzweiler.de/software/starstax/ and https://www.cloudynights.com/topic/719318-stacking-data-from...

Re: Dragonfly: An optical telescope built from an array of off-the-shelf Canon lens

#74

Post by formerly_proven »

gammarator wrote: post #62
MeteorMarc wrote: post #42

How can multi-element lenses have less scattering than a large mirror telescope? Do they mean smaller diffraction patterns instead?

See the third page of https://arxiv.org/abs/1401.5473

Though the characterisation of nano-structured coatings isn't quite right

> However, the latest generation of Canon lenses features the first commercialized availability of nano-fabricated coatings with sub-wavelength structure on optical glasses.

Nikon was actually first to market with this, as far as I can tell in the AF-S 300mm f2.8 VR in 2004.

Re: Dragonfly: An optical telescope built from an array of off-the-shelf Canon lens

#75

Post by KeplerBoy »

lvspiff wrote: post #27
shiftpgdn wrote: post #16

Can someone smarter than me explain why astronmers can't stick something like this on the back of an existing geostationary platform (like what is used for the XM radio sattelites) and get amazing data out of them? Surely sticking something like this array 100km into space will yield better results without the overhead of a 20 year mission plan like James Webb or Hubble.

I've always wondered that myself - If the Russians could build and launch sputnik in 1957 and get it around the earth a few times why aren't we seeing a huge number of backyard dad+son duos building rockets to launch their own telescope array. Its amazing that its a 60 year old feat that is still only in the hands of governments and massive corps

Just because it was possible for the soviets back then, doesn't mean it's trivial today.

Rocket fuel is also not exactly easy to come by.

Re: Dragonfly: An optical telescope built from an array of off-the-shelf Canon lens

#76

Post by TeMPOraL »

Aspos wrote: post #43
antognini wrote: post #11

This kind of a setup of a large number of small, cheap detectors works well for observing diffuse objects with low surface brightness. Generally speaking telescopes improve with size because larger telescopes can resolve smaller objects, so you can concentrate the light from your source into a smaller patch and increase the signal-to-noise with respect to the background. But once you have resolved the object (which d…

Can one use millions of smaller detectors if one finds a way to point them in one direction and synchronize them to take pictures at the same exact moment? I mean, can millions of phone cameras make one giant virtual telescope?

Now, maybe. Soon - not really, as AI features in camera apps will erase weak signals and/or replace them with some creative interpretation of a generative model. COTS cameras are increasingly becoming useless for doing science.

Re: Dragonfly: An optical telescope built from an array of off-the-shelf Canon lens

#77

Post by criddell »

TeMPOraL wrote: post #76
Aspos wrote: post #43

Earlier quoted context omitted.

Can one use millions of smaller detectors if one finds a way to point them in one direction and synchronize them to take pictures at the same exact moment? I mean, can millions of phone cameras make one giant virtual telescope?

Now, maybe. Soon - not really, as AI features in camera apps will erase weak signals and/or replace them with some creative interpretation of a generative model. COTS cameras are increasingly becoming useless for doing science.

Are the AI changes also made on RAW format images?

Re: Dragonfly: An optical telescope built from an array of off-the-shelf Canon lens

#78

Post by gpderetta »

nico wrote: post #70
antognini wrote: post #11

This kind of a setup of a large number of small, cheap detectors works well for observing diffuse objects with low surface brightness. Generally speaking telescopes improve with size because larger telescopes can resolve smaller objects, so you can concentrate the light from your source into a smaller patch and increase the signal-to-noise with respect to the background. But once you have resolved the object (which d…

It’s interesting that technically an individual camera’s sensor is itself an array of smaller sensors that capture individual pixels. So you have like a tree of arrays Maybe we can keep stacking them. Build an array of arrays of cameras/telescopes What would be the limit?

The sky is the limit. Or the target at least.

Re: Dragonfly: An optical telescope built from an array of off-the-shelf Canon lens

#80

Post by dukeofdoom »

antognini wrote: post #11

This kind of a setup of a large number of small, cheap detectors works well for observing diffuse objects with low surface brightness. Generally speaking telescopes improve with size because larger telescopes can resolve smaller objects, so you can concentrate the light from your source into a smaller patch and increase the signal-to-noise with respect to the background. But once you have resolved the object (which d…

So that seems like it would be a great use for the Seeestar s50. There's a bunch of people that bought the Seestar s50. Which is a $500 smart telescope that is controlled with your phone, and can rotate and track objects in the sky. They're now distributed throughout the planet.
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