The Sloan Digital Sky Survey | Hacker News Reader

The Sloan Digital Sky Survey

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43 pointsdnetesn8 comments

For anyone interested in astronomy who would like to try their hand at some small projects using real data, the SDSS website has some guides to help you through a few projects here:

http://skyserver.sdss.org/dr14/en/proj/projhome.aspx

Some of the advanced projects are to make an HR diagram, classify stellar spectra, and calculate the redshift of quasars. Of course, all the data is public so the guides are just a start --- you can keep going in any interesting direction. It doesn't take long to get to the point where you're doing real research.

It's pretty cool that thanks to this project anyone with an Internet connection can reproduce fundamental astronomical results for themselves.

Even for a simple amateur astrophotographer [1] the SDSS data is invaluable. It powers most of the target selection, and provides accurate coordinates for most astronomical objects. Combined with Plate Solving, it makes my life much easier [2]. Take for example a well known tool "Sequence Generator Pro", I only have to type in a name and I can start imaging [3]. I can't thank the people enough who worked on this. I'm soon upgrading the telescope with a set of Sloan photometric filters (used in the survey) [4], and particularly interested in expanding my images with Near Infrared data. Which can also give very pretty pictures [5]

[1]: my 2017 images https://www.flickr.com/photos/joelkuiper/38496747325/

[2]: http://cosmo.nyu.edu/hogg/research/2006/09/28/astrometry_goo...

[3]: https://www.flickr.com/photos/joelkuiper/24582661547

[4]: http://astrodon.com/store/p12/Astrodon_Photometrics_Sloan_Fi...

[5] http://trappedphotons.com/files/tmp/Making%20Pretty%20Pictur...

The second link is fascinating. I've never come across this algorithm. What a clever solution!

I'm a bit unclear on how the "quads" are chosen (ie. which 4 stars are grouped together). I assume your image and the sky-survey database you're comparing to are at a completely different detail-level. Choosing every combination of 4 stars seems not practical. If you just choose groups of 4 that are next to each other then you may find the database has dozens of stars in between your quad's stars (b/c it's at a higher detail level)

The slides acknowledge this by saying " Finally, there is the additional problem of distractor & dropout stars", but I don't see their solution :)

Maybe this is a clue "Cycle through all possible valid* quads (brightest first) and compute their corresponding codes" but there are no details.

Nearly 10 years ago (wow, time flies), as a weedy undergraduate, I was fortunate enough to do a research project [1] under one of the scientists [2] who worked on this survey. It was pretty cool to just be able to submit arbitrary SQL queries and get nice CSV files back.

With my imperfect knowledge of astrophysics and hacked-up scripts, it was pretty intimidating to stand up and present my "interesting-but-will-probably-need-more-detailed-research" to a bunch of people with literally decades of experience in the field and have them take me seriously and ask questions.

I do other things now, but it's a pleasant surprise from the past to see this on here :)

[1] https://mandarg.com/vsrp-talk.pdf

[2] http://www.ncra.tifr.res.in/~yogesh/

I worked with probably a dozen or so scientists and engineers who were building the SDSS telescope and the associated data analysis infrastructure (full disclosure: my role was very nearly entirely nothing compared to everyone else).

It's really a technological marvel, and some truly brilliant engineers and scientists were working on it. I'm intensely gratified that the survey has been such a smashing success; they all deserved it.

The part I was always most impressed with was they way they took the spectra. As mentioned in the article, the survey was twofold: the image survey over the vast swaths of the sky and somewhere around 2,000,000 spectra taken of distant objects.

Every single one of those spectra was taken by use of a fiber optic cable at the focus point of the telescope. They would take a metal plate, drill holes in it where the objects would appear, and plug the holes by hand with the cables: http://blog.sdss.org/wp-content/uploads/2014/05/twitter5.jpg

2 million times!

I was pretty lucky to be in a department that was one of the SDSS members. The metal plates they had were only used a few times since each one was unique to the field it was designed for. After they were done with them they sold them to some of us grad students for $20 (the price they would have gotten as scrap). When I move into a house I'm going to mount mine on a wall so I have a little piece if scientific history to look at. :)

One thing to add, too, is that the plates are pretty big! Each one is about three feet across and maybe 1/8 inch thick!

On the radio astronomy side. The Jansky VLA survey has only just begun data collection ;)

https://science.nrao.edu/science/surveys/vlass

https://sciencesprings.wordpress.com/2017/12/28/from-nrao-th...

The most recently run catalog of the sdss has some very interesting coding techniques associated with it:

https://youtu.be/uecdcADM3hY?list=PLP8iPy9hna6QpP6vqZs408etJ...

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