Posted by
Herbie on
Mar 01, 2016; 9:57am
URL: http://imagej.273.s1.nabble.com/Question-Can-image-J-make-a-Pixel-value-brightness-chart-tp5015749p5015752.html
Good day Thomas,
yes, the video was quite helpful for getting an idea of the issue!
And no, I've no experience with astro-images but...
My impression is, that there are several non-moving objects that change
their intensity over time which makes simple frame to frame subtraction
worthless. Consequently the moving object, the satellite, should somehow
be tracked. There are ImageJ-plugins that are made for this but I've
never used them. However, there may be a simpler approach if the track
is more or less known. You could select the track---i.e. make it an
(elongated) ROI (region of interest)--and perform frame to frame
subtraction restricted to this ROI. If the background is sufficiently
stable, this approach isolates the object and it should be rather easy
to determine its gray value in every frame.
You may just try the approach using a few frames and if it works you may
write a little ImageJ-macro to automate the procedure.
HTH
Herbie
:::::::::::::::::::::::::::::::::::::::::::
Am 01.03.16 um 01:51 schrieb Thomas Dorman:
> On Monday, February 29, 2016 5:46 PM, Thomas Dorman
> <
[hidden email]> wrote:
>
>
> HerbieThank you for your reply. I have a video of the North Korean
> KMS 3-2 satellite passing through the field of view of my camera. The
> satellites magnitude is varying as it tumbles. Was wanting to create
> a chart showing the brightness variation of the satellite as the
> satellite crosses the field. We are able to break the video down in
> individual frames if needed.We know Image J is used a lot for micro
> imaging but some people are using it for Astronomy. Do not know if
> any one is attempting what we are trying to do with Image J. If it
> would help to see the video it can be found here in three version
> where others and you can understand what we are trying to
> do.
http://vid284.photobucket.com/albums/ll34/skyflash_14700/KMS-3%20final%20video%201A_zpsmguano8n.mp4>
>
Thanks you once again for your reply and any help in
advance.RegardsThomas Dorman
>
>
> On Monday, February 29, 2016 4:35 PM, Herbie <
[hidden email]>
> wrote:
>
>
> Good evening Thomas,
>
> it would be quite helpful to know what you mean by "Pixel value
> (brightness) chart". I'm in the field of image processing for about
> 40 years but have never heard of this.
>
> Is it the collection of the (gray)values that actually are present in
> an image or is it the (gray)value histogram of an image?
>
> For the rest of us, please be more specific.
>
> Best
>
> Herbie
>
> ::::::::::::::::::::::::::::::::::::::::::: Am 29.02.16 um 23:07
> schrieb Thomas Dorman:
>> Can image J create a Pixel value (brightness) chart from a set of
>> images or a video? If so where can we find the instructions to do
>> so?RegardsThomas Dorman
>>
>> -- ImageJ mailing list:
http://imagej.nih.gov/ij/list.html>>
>
> -- ImageJ mailing list:
http://imagej.nih.gov/ij/list.html>
>
>
>
>
> -- ImageJ mailing list:
http://imagej.nih.gov/ij/list.html>
>
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