Is the difference between this and a normal telescope that it has a wider field of view for the same level of detail? So you could do the same thing more slowly by taking hundreds of pictures in different directions with a normal telescope?
Correct, the camera is built for an all sky survey. With the wide field of view it should be able to image the full night sky once every two or three days.
Yes, and to amplify, part of the utility is in its ability to observe transient phenomena. As we have been able to do more large-scale surveys, and scan the resulting images with transient detection software, we have observed a lot of surprises. LSST is designed to step that up by a lot.
It depends what you mean by a "normal telescope" (all telescopes used for astronomy are designed for specific tasks/roles, even if that's not called out in public-facing material as much). LSST is not the first large scale optical survey (and previous telescopes have chosen to have a wide field of view, but they've been quite small in comparison), and there are tradeoffs to trying to use such a large field of view (e.g. having to correct for lots of distortions, both in the design of the optics, and in software), but because of the large collecting area (being a 8-meter class telescope), you can go much fainter faster (and with higher signal to noise) than a 1-meter class telescope that has the same field of view. Wikipedia has a bit about what makes LSST special (https://en.wikipedia.org/wiki/Vera_C._Rubin_Observatory#Comp...). I don't know when they're going to start observations, but I suspect there'll be loads of announcements of cool new transients soon after.
The other difference is partly a consequence of the wide field of view. That thing has a huge front lens, which lets in a massive amount of light, so the brightness of the projected image on the sensor is much higher than a telescope that has a zoomed-in field of view. That means it is able to use a relatively short exposure and still see things in the sky that are fairly dim.
To use numbers to compare to any other camera, it has a 3.2 gigapixel sensor with a diameter of 640mm, and the "lens" (actually several mirrors) has a focal length of about 10m and a diameter of about 8m, giving it an f-ratio of f/1.2, which is very impressive (although the central part of the "lens" is obstructed, giving it a light-collecting ability more like an f/1.5 lens).
The Rubin telescope, like all larger telescopes, doesn't have a lens. It has a 27ft main mirror. I think the big difference is the size of secondary mirror which is 11ft in diameter.
It can be compared to the neighboring Gemini South telescope which is similar size but has 3ft secondary and f16 focal length.
I'm curious about the project's early designers; could they foresee the current impact of satellite constellations on earth-based observations? How might it have influenced the system design and/or planned operations?
Good question. LSST was being studied as early as 2008, and it was highly ranked in the 2010 Astrophysics decadal survey - I just looked it up and in that 2010 survey the design was described as “relatively mature.” This was long before the Starlink issue became known, e.g. the first Starlink launch was in 2018.
I worked in this area around 2008-2014 and I never heard astronomers discussing communication satellite interference, it was mostly about data volume, image processing, and automated classification. Perhaps it was being considered in the later 2010s by serious optical system engineers?
I recall reading that the interference could easily be cancelled out by professional and institutional researchers using known data on the satellite’s location.
Not sure if that’s still the case several years later, or if it was just a deliberately crafted press release.
It was being studied well before that. I think Tony Tyson had the design in the 90s. I know serious work started around 2003 with the creation of LSST Corporation. Funding dripped in with some stimulus aid, and then ~2014 was when much of the funding started to come in for construction.
I don’t recall when the original operations date was anticipated to be, but I know they probably thought it’d be online in ~2017 in the 2000s. Before Covid, it was 2023 ish.
It probably would have been clearer if the article said 3.2 gigapixel. My first reaction was bewilderment at the excitement over a 3.200 megapixel camera (yes I misread the comma).
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To use numbers to compare to any other camera, it has a 3.2 gigapixel sensor with a diameter of 640mm, and the "lens" (actually several mirrors) has a focal length of about 10m and a diameter of about 8m, giving it an f-ratio of f/1.2, which is very impressive (although the central part of the "lens" is obstructed, giving it a light-collecting ability more like an f/1.5 lens).
It can be compared to the neighboring Gemini South telescope which is similar size but has 3ft secondary and f16 focal length.
I worked in this area around 2008-2014 and I never heard astronomers discussing communication satellite interference, it was mostly about data volume, image processing, and automated classification. Perhaps it was being considered in the later 2010s by serious optical system engineers?
Not sure if that’s still the case several years later, or if it was just a deliberately crafted press release.
I don’t recall when the original operations date was anticipated to be, but I know they probably thought it’d be online in ~2017 in the 2000s. Before Covid, it was 2023 ish.