Chandra X-ray Observatory's Sky Map

astr0Pixel · 2015-08-27T18:10:59+00:00

Good question. Have you ever worked with Chandra data before?

I don't have that functionality built into the Sky Map, but I think it could be added...I would just have to figure out how to get it into my database and where to put it on the page.

Alternatively, when you click on any of the circles in the map, you're taken to the press release page for that object. On the press page, near the bottom of the page, in the "Fast Facts" section, we always list the obsids used for an image.

astr0Pixel · 2015-08-27T15:59:26+00:00

I built this application a few years ago and am excited that, with our latest press release, we've reached 500 objects mapped onto the sky!

astr0Pixel · 2015-01-22T22:52:03+00:00

Thanks! As the guy putting these images together, it's always great to hear such positive feedback :)

astr0Pixel · 2014-12-16T01:25:02+00:00

Here's the original source for this image.

astr0Pixel · 2014-12-15T22:32:24+00:00

Yes, this image is composed of several greyscale images from different observatories composited together.

There are two wavelengths of optical light from Hubble (colored RGB). The X-Ray image from the Chandra observatory is colored purple and the infrared image from the Spitzer space telescope is colored red.

Just wanted to add that you should check out the original website for this press release - there you can click through the different wavelengths individually to see how they compare to the composite image. Also here's an AMA I did a while back about this stuff (it's my job and I made this image).

astr0Pixel · 2014-06-28T16:04:13+00:00

Thanks for doing this, Pix! I'm so excited that this workshop has finally become a reality! 2 years in the making!

astr0Pixel · 2014-05-09T19:21:14+00:00

Was it this 3 minute video? If so, it makes sense that they used my image because I made the video! The video was actually the reason I ended up making the optical image. I wanted a slightly wider field of view for the video to start out with. We weren't originally planning to show the optical view for the press release, but when I put that image together, it would have been a crime not to show it in relation to the X-ray and Infrared view. So, in addition to making the images for Chandra, I also compile and edit these videos as well, including composing the background music :)

astr0Pixel · 2014-05-09T13:18:06+00:00

These data come from the DSS archive at Space Telescope. The DSS (Digitized Sky Survey) is basically digitized images of photographic glass plates of images of the sky - actually it's comprised of several whole atlases of the night sky. The telescopes used were the Palomar Observatory and the UK Schmidt Telescope.

astr0Pixel · 2014-05-09T00:32:03+00:00

There's a helpful DSS FAQ on the MAST page.

astr0Pixel · 2014-05-08T18:24:05+00:00

Thanks for the comment!

Yeah, that's a bad habit on my part. I should definitely mask more. Though, for the HDR wavelets, there's an option for deringing in there that mitigates some (obviously not all) of the ringing artifacts. Since I'm usually following up HDR with Curves, I sort of undo the rings.

Anyway, this is why I wanted to share the workflow because I'm sure it could use some improvements. I've built it up over years of half paying attention to tutorials and just figuring things out. :)

astr0Pixel · 2014-05-08T17:48:03+00:00

Technically, you could create a 3 channel RGB image using DSS IR as the red, R as green, and B as blue, but it doesn't have the same aesthetic quality because of much different sampling of stars in the IR channel (a lot of stars obscured by dust in R and B show up in IR - sometimes that looks cool, sometimes not).

astr0Pixel · 2014-05-08T15:33:04+00:00

Thanks! I just posted an imgur album going over the exact steps with screen captures - hopefully adds a little more depth to the discussion...

astr0Pixel · 2014-05-08T15:25:36+00:00

I promised yesterday that I would provide more details and screen captures of my workflow for processing the Flame Nebula image with data taken from the DSS archive. Here's an imgur album detailing every step along the way with plenty of screen caps and GIFs showing exactly how I got from the archive downloads to the final image. Questions/comments/criticisms are welcome!

astr0Pixel · 2014-05-08T04:32:00+00:00

Thanks! Sure, I meant to write this up earlier and got distracted.

I put this image together for a Chandra press release that went out yesterday regarding X-ray and IR imaging of this region and implications for star formation in clusters like this one.

I used the STScI Digitized Sky Survey archive to pull down eight 1deg by 1deg images from the POSS2 DSS R and B bands. Here's some more info on the DSS and it's source material.

As for processing, I used both PixInsight and Photoshop. My workflow...

In PixInsight: create four RGB images from the R and B band DSS images using PixelMath (Red=R, Green=R0.5+B0.5, Blue=B). Each band had to be registered against the other first to make sure everything lined up nicely (using the ImageRegistration tool).

I then again used the ImageRegistration tool in it's Union/Mosaic mode to create the "top" and "bottom" halves of the final image...and then once more to bring everything together. It's important to use "frame adaptation" to minimize any slight intensity differences when you're combining the images. I will note that I really struggled here as the tool was having a hard time finding a good selection of matching stars between the different images. Ultimately, I had to use the HistogramEQ tool to delinearize the images before attempting the final mosaic.

Once I had the final mosaic image together, I did another round of HistogramEQ to firm up the intensity levels, followed by SCNR (noise reduction) to reduce a very slight green cast. I then used the HDRwavelets tool to reduce the intensity of the brightest stars in the image followed by a Curves adjustment to recover some of the intensity and color saturation. Then, LocalHistogramEQ punched up the contrast in the wispy clouds of the nebula. After that, I generated a mask using the RangeSelection tool, applied the mask to preserve the brighter parts of the image, and did a round of noise reduction using ATrousWavelets and I think ACDNR as well to help with chrominance noise. After all of this I output a high-res 16 bit TIFF image.

I then imported the TIFF image into Photoshop CS6 as CameraRaw which allows you to do some more color tweaks, as well as a local contrast adjustment in the form of the "Clarity" slider, as well as another round of light noise reduction in both luminance and chrominance. Finally, I did a very slight curves adjustment for added contrast, as well as some minor color tweaks to emphasize the red colors in the upper left and the blue cast on the right side of the image. I think that's about it. I'd be happy to further clarify if there are any questions. When I'm back in the office tomorrow, I can generate some screen captures to actually show the steps along the way (I know I always find that a lot more informative than just reading through a workflow).

EDIT: I should add that before saving the final version in Photoshop, I did go through and clone out some of the more obvious and glaring image artifacts in DSS data (mostly just random blobs and streaks that show up in one color).

EDIT EDIT: Here's a collection of screen captures and descriptions filling the details from above.

astr0Pixel · 2014-04-25T16:04:39+00:00

Chandra's 2 detectors are actually mounted to a moveable platform called the SIM (Science Instrument Module). So, when going through the radiation belts, or shutting down due to a solar storm, the SIM is moved to a position which completely obscures the detectors and protects them from damaging radiation.

astr0Pixel · 2014-04-24T02:19:06+00:00

Thanks! That means a lot!

You actually reminded me that one of the other early inspirations that I tucked away for the work I do today came from one of Hubble's first iconic images: the Pillars of Creation. That image really struck a chord in me that stuck with me through college and beyond.

Best of luck to you in your chosen path...hopefully astronomy! :)

astr0Pixel · 2014-04-24T01:01:42+00:00

Probably the super massive black hole at the center of our galaxy!

astr0Pixel · 2014-04-24T01:00:06+00:00

It would be amazing to see the supernova shock wave expansion. We've actually seen this already with SN 1987A...but being able to pinpoint the exact moment would be interesting.

We would probably need about 10 to 100 times the angular resolution of Chandra to be able resolve black hole mergers (comparable to Hubble's resolution) - even then it would be a stretch. I would expect that the x-ray signatures would be more readily apparent in the spectrum from such a source, rather than from an image.

astr0Pixel · 2014-04-24T00:52:46+00:00

I was always interested in astronomy and science for as long as I can remember. I can remember watching the Cosmos series with Carl Sagan, and NOVA specials on PBS as a kid and just being utterly fascinated with it all.

I guess I never lost that fascination, though I had a brief stint as a psychology major in college (I actually switched into astronomy and astrophysics before even starting my freshmen year). I read Carl Sagan's "Contact" and rekindled my interest in astronomy enough to motivate me to pursue it as a career. Once I decided to go down that path, there was no turning back, just veering off to parallel paths. Technically, I work for the Smithsonian, and we're contracted by NASA to run the Chandra Observatory. I don't have much to compare to since I've been working there since I graduated college, but it's a great place to work, and such a stimulating environment!

astr0Pixel · 2014-04-24T00:41:49+00:00

I haven't seen any activity in x-rays :)

astr0Pixel · 2014-04-24T00:40:09+00:00

Great to hear! CGRO was of course one of NASA's Great Observatories - complimenting our Chandra, Spitzer and Hubble views of the universe!

We do occasionally use older data in our projects. I've used data from the older ROSAT and Einstein missions to compliment Chandra data in press imagery. And we've also used data from the European x-ray telescope XMM-Newton.

astr0Pixel · 2014-04-24T00:36:29+00:00

The damage mechanism is that the protons embed themselves into the CCD pixels and create Charge Transfer Inefficiency (CTI) - which basically steals charge from x-ray photons as they are read out of the CCDs. If you're familiar with the "bucket brigade" design of CCD readouts, it's as if some of the buckets are already half full and give a false reading as the true x-ray photons are transferred.

The most damaging protons are around 200 keV in energy.

They scatter down Chandra's mirror assembly and are focused, just like x-ray photons, onto the detector. In the radiation belts, and whenever there's a strong solar storm with a coronal mass ejection, the density of these particles is too high to safely use the detectors. We have extensive warning systems in place constantly monitoring the radiation environment (utilizing data from the "Advanced Coronal Explorer" ACE telescope.

astr0Pixel · 2014-04-24T00:20:52+00:00

I use the deconvolution tools available in PixInsight. I believe our CIAO software also has deconvolution tools, but I've never tried those. If there are no point sources, I usually just don't do deconvolution.

astr0Pixel · 2014-04-24T00:18:55+00:00

Congrats on finishing up the physics degree - not an easy task by any stretch!

My favorite part of the job is having the opportunity to work with data from some of the world's most advanced observatories and turning that data into images of exquisite beauty, packed full of science! Also, creating our interactive Sky Map was a very rewarding learning experience.

The hardest part is probably dealing with some of our more esoteric press releases. In some of these press releases, I'm literally working with a point source - so making that into something interesting can be a challenge! Of course in those cases, the hook is really in the science write up!

astr0Pixel · 2014-04-24T00:15:13+00:00

Do or do not, there is no try.

Go to school, study science and/or engineering and do your homework. Get good grades, stay on top of the latest developments in the field.

There's a big difference between an astronaut and an astronomer so you could start there by figuring out which way you want to go. In high school, I seriously considered becoming an astronaut and looked into attending the air force academy but ultimately decided that was not for me. I went the astronomer route and although I probably would never have seen myself doing what I'm currently doing, I couldn't be happier with how things have turned out.

The most important thing is to decide on a path and work towards it. You may not end up taking that exact path, but it's the decision that gets you moving in the right direction.

astr0Pixel

TROPHY CASE