Rubin Observatory's first LSST Camera release: 500k galaxies in the COSMOS field • Hacker News Board

Re: Rubin Observatory's first LSST Camera release: 500k galaxies in the COSMOS field

#21

Post by binarystargazer » Thu, Aug 06, 2026, 2:31 PM UTC

skybrian wrote: post #18

irickt wrote: post #4

Viewer from Aladin Sky Atlas https://skyviewer.app/explorer

This is tricky to navigate because most of the sky survey hasn't happened yet. You need to zoom way out and look for patches that are mostly, but not completely black. And that gives you an idea of how huge the map will be once they've filled more of it in. Presumably it will get easier after more of the survey is done, but having a list of bookmarks instead of just one might be nice?

If you click on the search icon, there are some quick links to fields across the sky so you don't need to scroll as much. There are some interface tweaks and ui stuff that will be coming down stream that will help with some of this as well.

Re: Rubin Observatory's first LSST Camera release: 500k galaxies in the COSMOS field

#22

Post by binarystargazer » Thu, Aug 06, 2026, 2:39 PM UTC

doodlebugging wrote: post #15

This is great! I love to meander thru data like this trying to understand what I am looking at. I found a couple of things that are probably processing artifacts from the spectral filtering and selection of colors. One of them is a bright blue dipping segment that looks out of place. I can see blue filter artifacts on many of the starbursts. This one is very coherent but only for a short interstellar distance. I have…

Most of the artifacts you see are actually asteroids. We don't take all the colors at once when making an image. The ccds just count photons that fall on them, so we have giant glass filters that allow specific wavelengths through. We then image the fields multiple times with multiple filters and then map the wavelengths of light into color images (see other post about trying to make them as perceptually correct as possible). However, because taking multiple images over time means that things which are changing (i.e. moving asteroids) not not appear at the same places when we combine them. Most of the time these time changing effects get filtered out in the combination step, but sometimes if they are bright enough, or persistent enough the make it through.

As an FYI, you can right click in the sky viewer and it will show the coordinates of the object, and there is a button to copy a shareable link that will take anyone right to where you are looking in the sky.

Re: Rubin Observatory's first LSST Camera release: 500k galaxies in the COSMOS field

#23

Post by ricksunny » Thu, Aug 06, 2026, 3:09 PM UTC

binarystargazer wrote: post #14

thegrim33 wrote: post #11

Earlier quoted context omitted.

I hope the data releases are a bit better than what I've seen from recent telescopes. The common pattern seems to be that the majority of data is locked away behind multi-year embargo periods, or never released to the public at all with no explanation why, with only the smallest little crumbs of raw data actually released to the public, and usually years out of date. Also you have to go through some kafkaesque chain…

We are getting pretty far outside my area of expertise / knowledge on this topic here, but I know I and others agree with you here. There is a Rubin Observatory data access policy out there. Don't quote me on the exact specifics but I believe that most colleges and research institutions already have a mechanism to enable data access setup, or can get one. This is mostly an id auth type thing to make sure those access…

Curious what were your thoughts about this story when it broke: https://www.theatlantic.com/science/archive/2024/12/vera-rub...

And whether it impacts your work? For example, if the unnamed agencies' efforts leave a telltale mark in areas they change, that would still be problematic, so presumably they have to place noise corresponding to adjacent pixels. Are you concerned about how data integrity affects your work output? Penny to understand the internal scuttlebut / any internal grousings about this.

Re: Rubin Observatory's first LSST Camera release: 500k galaxies in the COSMOS field

#24

Post by doodlebugging » Thu, Aug 06, 2026, 9:21 PM UTC

binarystargazer wrote: post #22

doodlebugging wrote: post #15

This is great! I love to meander thru data like this trying to understand what I am looking at. I found a couple of things that are probably processing artifacts from the spectral filtering and selection of colors. One of them is a bright blue dipping segment that looks out of place. I can see blue filter artifacts on many of the starbursts. This one is very coherent but only for a short interstellar distance. I have…

Most of the artifacts you see are actually asteroids. We don't take all the colors at once when making an image. The ccds just count photons that fall on them, so we have giant glass filters that allow specific wavelengths through. We then image the fields multiple times with multiple filters and then map the wavelengths of light into color images (see other post about trying to make them as perceptually correct as p…

Thank you for this useful reply. I appreciate the description of image building using the glass filters. That makes sense to me. The asteroids seem like an imaging issue that would be difficult to deal with since they are likely near-field objects that are in motion relative to far-field objects. That would also explain some of the trails that one sees if the objects along that trail are the same object imaged over a multi-step process.

I figured there had to be a way to get real coordinates so that people could do research but I was not bright enough to push the buttons to find that link and had to use the tool I hate - Snip & Sketch. I have a license for SnagIt and Greenshot on another workstation, either of which is better than S&S but that installation is inaccessible due to hardware issues.

Thanks for helping to make it easier to use these images!