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Vera C. Rubin Observatory first images

rubinobservatory.org

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Re: Vera C. Rubin Observatory first images

#3

Post by NitpickLawyer »

So stoked for this observatory to go online! One cool uses it'll excel at is taking "deltas" between images and detect moving stuff. Close asteroids is one obvious goal, but I'm more interested in the next Oumuamua / Borisov like objects that come in from interstellar space. It would be amazing to get early warnings about those, and be able to study them with other powerful telescopes we have now.

Re: Vera C. Rubin Observatory first images

#5

Post by NitpickLawyer »

jasonthorsness wrote: post #4

Why are there lens-flare-like artifacts around some of the bright objects?

Those are diffraction spikes, caused by how the light interacts with the support structure holding the secondary mirror. Each telescope has different patterns, hubble, jwst, etc. I think they only happen for stars, and not for galaxies (an easy way to know which is which), but I might be wrong on that (there's a possibility for faint stars not to have them IIRC).

Re: Vera C. Rubin Observatory first images

#6

Post by perihelions »

Here's the SDSS view[0] of this featured[1] section from the Virgo Cluster, in comparison, to put the staggering depth of these exposures in their proper context,

[0] https://aladin.cds.unistra.fr/AladinLite/?target=12%2026%205...

[1] https://rubinobservatory.org/gallery/collections/first-look-...

Re: Vera C. Rubin Observatory first images

#7

Post by perihelions »

NitpickLawyer wrote: post #5
jasonthorsness wrote: post #4

Why are there lens-flare-like artifacts around some of the bright objects?

Those are diffraction spikes, caused by how the light interacts with the support structure holding the secondary mirror. Each telescope has different patterns, hubble, jwst, etc. I think they only happen for stars, and not for galaxies (an easy way to know which is which), but I might be wrong on that (there's a possibility for faint stars not to have them IIRC).

> "Each telescope has different patterns"

This one's extra-special! The pattern is multiple + shapes, rotated and superimposed on top of each other. And they're different colors! That's this telescope's signature scanning algorithm—I don't know what that is, but, it's evident it takes multiple exposures, in different color filters, with the image plane rotated differently relative to the CCD plane in each exposure. I assume there's some kind of signal processing rationale behind that choice.

edit: Here's one of the bright stars, I think it's HD 107428:

https://i.ibb.co/HTmP0rqn/diffraction.webp

This one has asteroid streaks surrounding it (it's a toggle in one of the hidden menus), which gives a strong clue about the timing of the multiple exposures. The asteroids are going in a straight line at a constant speed—the spacing and colors of the dots shows what the exposure sequence was.

I think this quote explains the reason they want to rotate the camera:

> "The ranking criteria also ensure that the visits to each field are widely distributed in position angle on the sky and rotation angle of the camera in order to minimize systematic effects in galaxy shape determination."

https://arxiv.org/abs/0805.2366 ("LSST [Vera Rubin]: from Science Drivers to Reference Design and Anticipated Data Products")

Re: Vera C. Rubin Observatory first images

#8

Post by dekhn »

I really like the Rubin because I think a lot of people focus too much on "deep" seeing (IE, looking at individual or several objects with very high magnification only once). The Rubin does much more "wide" seeing and this actually produces a ton of useful data- basically, enough data to collect reliable statistics about things. This helps refine cosmological models in ways that smaller individual observations cannot.

What's amazing to me is just how long it took to get to first photo- I was working on the design of the LSST scope well over 10 years ago, and the project had been underway for some time before that. It's hard to keep attention on projects for that long when a company can IPO and make billions in just a few years.

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