CEERS/JWST DATA

Gary Palmer

On the CEERS/JWST website, I’m encountering files that look like the one in the top JPEG image below (both before and after converting to RGB). The red was intended to reveal all the empty (black, $T==0) pixels in one view, as demonstrated in the Adam Block video Fundamentals: Useful PixelMath, but for some reason the red appears to have filled the white pixels instead. Perhaps this unexpected behavior has something to do with some fault in the file.



To me these data look almost hopelessly noisy, but the CEERS images look good, and they are ostensibly produced with these same data. See, for example this panel from the CEERS website. But I have a hard time developing these files. The controls for HistogramTransformation and GeneralizedHyperbolicStretch become very sensitive or unresponsive, as though they were beyond normal range.

Does anyone on this master forum have any idea into how to proceed?

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P. S. All the pertinent NIRCam monochrome image files are downloadable at the CEERS page for the STSCI Mikulski archives. When opened in Pixinsight, each file will is accompanied by nine ancillary files that can be discarded. One need keep only the file coded “SCI” in the filename. Any one of the 26 NIRCam files for the CEERS mosaic would probably illustrate my point equally well, though I have myself only looked at the files for pointings numbered 1, 2, and 6.

I have posted a messages regarding the CEERS/JWST data on the Pixinsight Forum and Cloudy Nights.

    
    

BlockHead

Hi Gary,

I do not have the ability to dive in at the moment..but, I will say that the JWST data I worked with when I processed the Fomalhaut debris disk... had an arbritrary range of values (including negative values). This is normal for their data. You want PixInsight to import the files and automatically find the low an high values... then it will import the image making all of the values go from 0-1 just as you normally have.

I suspect this is part of your issue. Do you think I am on the right track?

-the Blockhead

Gary Palmer

I think it is quite possible that you are on the right track. I know when I inspect them in FITS Liberator that they show negative values. I did import the above file with Pixinsight and the max and min are evident in the screen shot that I included, but I don't know whether this means that PI included the negative values.

But for some reason, the screen shot does not show up in my posting above. I see only "image" and it is not an active link to the file in my OneDrive account. I will try attaching it.

BlockHead

In the File Format explorer for FITS you can change the method that it loads FITs files so that it loads it by range.

-the Blockhead

Gary Palmer

I anticipated this and tried  {0, 1}, {0, 65535} {0, 4.294967296000000e+09}, {-1,1}, {-65535, 65535}, ....

The result for {0,1} and {-1,1} was almost identical (differed by .001 on min in Statistics) and looked identical under STF. The result for {0,65535} was identical to these.

With {-65535, 65535}, I got max = min = mean = med = 32767.500, which doesn't seem useful. The appearance under STF was very solarized. With the range {- 4.294967296000000e+09, 4.294967296000000e+09}, Ithe result was the same.

Gary Palmer

If I select truncating the out of range values, the clipping in the shadows is extreme.

BlockHead

Correct.. you do not want to do that!

Did you watch my video on my working with the FomalHaut data on YouTube?

-the Blockhead

Gary Palmer

I tried to find it in your list of videos, but I hadn't looked on YouTube yet. I will now.

BlockHead

Well..I do have a list on my site that links to the YouTube videos.

I think it is current...

-the Blockhead

Gary Palmer

I watched the video and payed particular attention to the manipulations of the STF triangles. It was amazing to see the star jump out from such faint data. But with this data from CEERS Pointing #2, I find that whether I work with a monochrome image or an RGB combined image, the STF triangles come up on the extreme left. I move the top (they are superimposed) triangle to the right a bit, and then I can see the bottom one. If I try to move the bottom one and I'm very careful, I can get some semblance of an image without obvious noise, but I have less than 1 mm of play before the image goes dark or saturated with color. I just realized that I can manipulate the STF without using the yellow wheel, so I will try that. The result is the same. The triangles end up in the last millimeter on the left and the image is dim but clean.

BlockHead

Can you make the image you are talking about available to me?

-the Blockhead

Gary Palmer

Here is a link where it can be downloaded. But there is nothing special about it. Any of the downloadable files at the CEERS page referenced above would serve as well.

BlockHead

Hi Gary,

OK..I grabbed the file. I do not see an issue?

There are no zero values. Everything looks good. 

Nothing Red shows up, the statistics look fine.

The STF looks fine. I am able to zoom into the STF and manipulate the black point and midtones value.

(Is the issue you cannot zoom into the STF process?)

I think we need to start again on this... what is the issue?

I think I need more screenshots. 

-the Blockhead

Gary Palmer

Hi Adam,

The issue is that my ignorance of how to use STF was profound. As you noticed, I didn't know how to use the zoom function, but it is a bit tricky, as you noted in the video STF and HistogramTransformation. I think the video has given me the information I needed. I hope you will agree after looking at the screen shot. It was a real delight after my struggles with the carets to watch you dealing with the disappearing and crowded carets. I used the buttons in STF to set the light, mid, and dark points in the attached image.

I still don't understand why my attempt to use the red channel to highlight zero pixels went wrong, but that is not a big issue.

Thank you very much for the attention to my JWST efforts. I'm looking forward to working on some more pointings. Something new and interesting, and often unmentioned by the CEERS developers, seems to turn up in every image.

Gary

BlockHead

Hi Gary,

Actually.. the video you want to see are the ones in Stretch Academy.

This one in particular!

https://www.adamblockstudios.com/articles/stf-utilization

I will add these videos to the STF section so that people can find them.

-the Blockhead

Gary Palmer

Adam,

I agree. I watched that one this morning and got a lot out of it. Since then I've been trying to apply the techniques in those two videos by continuing work on CEERS Pointing #2. I will attach a few small jpegs. This pointing did not have as many spectacular features as some others, but there are always things of interest.

I am trying to post multiple small files, but the upload has hung on the second. I'll put the rest in a folder on OneDrive.

Gary