Slicing the Images

The images that I have been showing you do not look at all like the originals that come to me from the telescopes.

For the recent images I took of Philosophia, here is what the first image actually looked like, originally:

Here is what it looks like after I do my gray-scale "slicing".

Here is an indication of the approximate part of the image that I zoomed in on for my previous few posts:

And finally, here is that zoomed in subset of the gray-scale sliced image.  (You've already seen this in previous posts.)

What is Slicing?

So, what is this grayscale "slicing" thing?
It is a kind of super contrast enhancement, but only for the gray values I know I care about.

The original images I receive are 16 bits deep, and have very little noise generated by the cameras themselves.  That means these are very fancy images, from very fancy cameras.

Here is the camera that I get to use on t27 :

That, ladies and gentlemen, is a PL09000 from a group of genius philosopher/monk/engineers called Finger Lakes Instrumentation, and it will set you cack a cool $10,000 if you get a deal on it.  Until we get the LSST, this is one of the very best imaging devices on this little blue planet.

The image that this beauty produces has 256 times more dynamic range than what our eyes can see on a screen.  (Actually, more like 1024 times, but whatever.)  Its images have 65536 different levels of gray.

But since my eyes can really only see 64 t one time, and since I want to be able to actually see the interesting things while I am trying to write software to find them automatically, here is what I do:

I select a small portion 1/256 of all the available gray values, and I map them onto the whole grayscale.  I call this set of grayvalues a "grayscale slice".

I know which set of 256 values I want, because I only care about the faintest streaks -- just above the sky-noise, which means just above the most common gray-value in the image, which is easy to find.