Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

dunlap.utoronto.ca

Post reply on HN
Print view View original

21–30 of 82 posts

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

#21

Post by perihelions »

jcims wrote: post #17
perihelions wrote: post #13

Earlier quoted context omitted.

- "diffuse objects with low surface brightness" Are things amateur photographers with small telescopes (and lots of patience) sometimes discover, https://old.reddit.com/r/space/comments/13uco46/i_discovered... ( "I discovered this planetary nebula using a $500 camera lens, now it carries my name" ) https://www.astrobin.com/i9yy6f/ (18 hours!)

I still don’t understand how objects in space of that angular diameter are still being discovered. I would have to imagine lots of people have seen it, but just never chose to document or catalog it?

This is an extremely long (18 hour) exposure in specialized narrowband spectral filters that have no usefulness for anything other than these particular targets.

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

#22

Post by consp »

VohuMana wrote: post #19
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.

Not a professional so take this with a grain of salt but my guess would be weight first and foremost. From what I understand geostationary orbit isn’t cheap to get to and each added kilogram increases cost significantly. These lenses while not incredibly heavy are heavy enough to add a fair amount of cost.

I also doubt these lenses will hold up in a very cold or very hot near-vacuum.

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

#23

Post by sgt101 »

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 am no expert, but the things I would worry about:

- cost to get into geostationary orbit might dominate the value/saving of the cheap instrument, so it might be smart to spend more on that - managing and controlling it might be very challenging - need to get the data down from it - might create difficulties and costs that kill the value - heating and cooling in space might kill it - radiation in space might kill the hardware - acceleration during launch might kill the hardware - the payload needs to be stable during launch or there will be an accident - scientific value might be lower than other missions for similar spend

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

#24

Post by gridspy »

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.

The lenses are made of materials that will not resist the conditions in space (high temperature gradients, oxidizing environment, radiation).

Once in space they cannot tweak the array.

Launch weight and stresses would damage this array.

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

#25

Post by dekhn »

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.

Projects like this have been done; see for example https://www.jpl.nasa.gov/missions/arcsecond-space-telescope-...

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

#27

Post by lvspiff »

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

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

#28

Post by dekhn »

buescher wrote: post #10
1024core wrote: post #5

RAIT (Redundant Array of Inexpensive Telephoto lenses)?

Not that inexpensive - that's a $12000 lens with a nearly 6" aperture. The telescope itself is a fairly specialized instrument. It's more like a redundant array of very fast (for a telescope) lenses. From the paper: "Our primary goal is to test predictions that at very low surface brightness levels galaxies display a wealth of structures that are not seen at higher surface brightness levels." (But yes, the lenses are…

The thing to appreciate is that in academic science, $12000 lens is inexpensive; the scale is different from consumer and prosumer pricing. A typical project like this would get at least a million dollaras in funding (see https://www.artsci.utoronto.ca/news/astronomer-roberto-abrah... which shows they got $2M to buy lenses; 120 lenses * 12K = $1.5M.

I work with microscopes that cost $1M and just sit in a lab. That's not atypical for an academic or industrial microscope.

One of the biggest issues in modern science is that to make many discoveries you need to pay very high prices to get the latest and greatest hardware. I've been exploring how to make lower cost telescopes and microscopes (and definitely love this project), that are "good enough" to open up new areas of research/discovery for people with budgets in the $1K-10K range. But it's hard! So far I have mostly been relearning what people already knew in the 1800s and early 1900s, that is easily obtained off-the-shelf tech today.

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

#29

Post by perihelions »

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 don't think there's that big of an advantage for space-based astronomy here, for visible-wavelength light with large pixel scales, and relatively bright (total luminosity) objects. Because it's done in narrowband filters, it's particularly good at erasing sky noise.

/not an astrophotographer

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

#30

Post by ianburrell »

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.

Cause it wouldn't give better results. The big advantage of putting telescope in space is that don't have to deal with the movement of the air distorting the image. That doesn't matter when taking pictures of diffuse objects.

The disadvantage is that it is in space, you have to spend 10x or 100x as much making something that can work in space, and you can't maintain it. I bet it would be much better to spend that money making dozens of these around the world, or iterating on the design.

The other advantage is that atmosphere is opaque for some wavelengths. The infrared wavelength that JWST looks in are absorbed. It also helps to be able to cool down the detectors to lower temps. One reason we aren't seeing direct replacement for Hubble is that the big ground telescopes with active optics are as good.

Post reply on HN