New user question on opening *.fit files-three "gray" images open?

[Scott Fairbairn]

Hello,

I apologize for what must be, a very elementary question. I have gone through several video tutorials and tried searches, but I can't seem to find an answer to my question. When I open a *.fit file(I used another software program to combine, align and stack the image), I get three "Gray" windows that open. For example, the header on the image window reads, "Gray 1:4 CombineFilesExecAvg_compressed_image". Following the "image" name is "Image1, Image2, etc. for the three open windows.
I assume that I need to combine these three to get an RGB image, or even better, can I set the default opening to RGB?
Sorry if this is a very silly question, but I was very impressed with the video tutorials, and then stumped when I tried to open an image. This problem does not occur with *.tif images, they open in RGB, so I assume I am missing something obvious here?
thank you for your patience.
Scott

[Carlos Milovic]

There may be some information in the fits  header that is telling that the archive is containing several images, instead of a RGB image. As you may know, FITS allows to store several (multichannel) images in the same file, so it is important that the header information is correct.

[Scott Fairbairn]

Okay thanks, I'll try stacking, aligning from a different program as I have no idea how to change that information.

[Carlos Milovic]

You may do all these jobs right in PixInsight. See the BatchPreprocessing Script.

[shammo]

Scott,
I encounter this problem when I use CCDStack to combine the rgb's. Carlos posted this back in January in response to my question:
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Hi Scott

From what you said, it is possible that CCDStack is writing using a signed format. This means, instead of mapping the pixel values in the 0-65535 range, they are using -32768-+32767. Also, they may not be using the whole range, but only the positive values. That's the reason that the RAW image is displayed as grey.
PixInsight uses the normalized range as convention for every image, no matter the bitdeph. This means, internally everything is rescaled so 0 is black and 1 is white. Greys are fractional values in between.

One way to fix that would be to use PixelMath. Just type the following expression: "$T-0.5". This should also work, and be displayed a bit better: "($T-0.5)*2". Do not enable the rescale option.
Also, try searching in the forums. Maybe there is a little script somewhere to fix several files (a batch script). If not, it is not hard to do that with the PixelMath instance described above, and an ImageContainer.

Oh, also try searching for the "format hints". They are instructions that may be used to read the raw files by the calibration process, and a few others. It may also solve your problem.


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Hope this helps. Still trying to learn PI from the basics myself, I tabled it for a while do to time constraints, but have been seriously at it now for a few days. Time off from work and other things helps, but it is so different from other things I have used I feel like I am scaling a wall. The mosaic feature is awesome!

Scott Hammonds

[Scott Fairbairn]

Thanks for the help, I've not had too much time to devote to the program, but my gut feeling is that this is what I've been looking for. It just has a bit of a learning curve, like all things worth learning I guess. If only my skies would cooperate and let me try out some new data!
Thanks again.

[shammo]

Scott,
Since my last post I have jettisoned CCDStack for reduction, alignment and combine and I am a happy camper! I think when you have time to learn it, you will like these routines much better. It just takes a little perseverance and time. The video tutorials are invaluable.

Scott Hammonds