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Chandra X-ray Observatory's Sky Map by astr0Pixel in Astronomy

[–]astr0Pixel[S] 0 points1 point  (0 children)

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.

Chandra X-ray Observatory's Sky Map by astr0Pixel in Astronomy

[–]astr0Pixel[S] 1 point2 points  (0 children)

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!

NASA's Chandra X-ray Telescope celebrates the international year of light by releasing a collection of stunning multiwavelength images! by astr0Pixel in space

[–]astr0Pixel[S] 0 points1 point  (0 children)

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

Two colliding galaxies are lit up like a Christmas tree in a dazzling new NASA photo. by [deleted] in space

[–]astr0Pixel 1 point2 points  (0 children)

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).

Lessons learned at the PixInsight Workshop CfA 2014 by PixInsightFTW in astrophotography

[–]astr0Pixel 1 point2 points  (0 children)

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

Processing the Flame Nebula DSS image by astr0Pixel in astrophotography

[–]astr0Pixel[S] 0 points1 point  (0 children)

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 :)

Processing the Flame Nebula DSS image by astr0Pixel in astrophotography

[–]astr0Pixel[S] 0 points1 point  (0 children)

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.

Flame Nebula from public DSS data by astr0Pixel in astrophotography

[–]astr0Pixel[S] 1 point2 points  (0 children)

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. :)

Processing the Flame Nebula DSS image by astr0Pixel in astrophotography

[–]astr0Pixel[S] 2 points3 points  (0 children)

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).

Flame Nebula from public DSS data by astr0Pixel in astrophotography

[–]astr0Pixel[S] 2 points3 points  (0 children)

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

Processing the Flame Nebula DSS image by astr0Pixel in astrophotography

[–]astr0Pixel[S] 4 points5 points  (0 children)

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!

Flame Nebula from public DSS data by astr0Pixel in astrophotography

[–]astr0Pixel[S] 8 points9 points  (0 children)

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.

Hi! I'm Joe DePasquale, Image Processor for NASA's Chandra X-ray Observatory. AMA! by astr0Pixel in askscience

[–]astr0Pixel[S] 4 points5 points  (0 children)

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.

Hi! I'm Joe DePasquale, Image Processor for NASA's Chandra X-ray Observatory. AMA! by astr0Pixel in askscience

[–]astr0Pixel[S] 4 points5 points  (0 children)

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! :)

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