ASI 178MC no color in ASCOM

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ASI 178MC no color in ASCOM

Postby Pablo García » Thu Jan 04, 2018 9:37 pm

Shooting in ASCOM mode driver, the saved files are always written en B/N, but the preview screen show the image in color.

This problem has been observed in both App. APT and SharpCapture
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Re: ASI 178MC no color in ASCOM

Postby chad » Fri Jan 05, 2018 8:39 am

Hi Sir,
If you use the ASCOM interface in SharpCap, you should not see the color in the preview.
Because ASCOM interface only supports the raw data transfer.
If you can see, Please email the author of the software. I think they made a mistake.
Thanks
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Re: ASI 178MC no color in ASCOM

Postby Pablo García » Fri Jan 05, 2018 10:58 am

Hello, thanks for your quickly response, but the problem ist not the preview, but the saved FITS file.

As I understanding, in ASCOM mode the camera flow in Raw 16 has the needed information of color folowing the bayer color pattern.

In fact, the live view or preview of both apps (APT and SharpCapture) are showed in true color.

However, the FITS file (or PNG file in Sharpcapture) saved have only B/N information.

In the APT Forum (about the same problem with the ASI 1600 MC) they have the opinion that the problem is in the ZWO ASCOM drive.

What do you think about that?

Thanks
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Re: ASI 178MC no color in ASCOM

Postby MikeP » Fri Jan 05, 2018 12:16 pm

Image data from colour cameras in RAW16 format always needs to be 'de-bayered' to obtain a colour image. Most likely the preview in SharpCap and APT will do this for you so you see a colour image straight away.

When saved in FITS format the original RAW16 data is saved (not the colour version) and you need to run the 'de-bayer' process again in your image processing software to obtain a colour image from the FITS file.

Hope this helps.
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Re: ASI 178MC no color in ASCOM

Postby Pablo García » Fri Jan 05, 2018 8:09 pm

Ok, thanks. I understand the raw file concept (in fact I can de-bayerize raw files DNG from my DSRL)

But I have tried to open the FITS file generated by APT or SharpCapture thru:
-FITSliberator
-DeepSkyStaker
-AvisFV
- SIPS
- RegiStack

And all of them open the file as B/N (I think that because they can't de-bayerize it)

Any suggestion?
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Re: ASI 178MC no color in ASCOM

Postby MikeP » Sat Jan 06, 2018 11:13 am

What would you like to do with the image? When you open the raw fits data all the colour information is in there (i.e. every other pixel is representing a different colour according to the matrix) but unless you process that data by de-bayering it it will be displayed in black and white.

If you want a colour image from your fits file then you have to use some image processing software which can de-bayer fits images (most can). Once de-bayered you can then save your colour image in a different format e.g. png, jpg etc. (the fits format is not really designed to store colour image data like RGB).

If you want to stack your images then you usually de-bayer all images first and then stack them. Most stacking software packages can do the de-bayering for you you just have to provide the right settings.
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Re: ASI 178MC no color in ASCOM

Postby chad » Mon Jan 08, 2018 2:56 am

Hi MikeP,
Thanks for your answer.
I think his question is probably he doesn't know how the pixels show the color。
For ASI178MC, it have 3096*2080 pixels. Each pixel can only collect one of three colors (red, green ,blue). Therefore, they must be arranged according to certain rules. This rules was called Bayer. So the debayer is to tell the software which color on one pixel.
Each pixel also has a value, This value just shows how much light the pixel has collected。

So if you want to see a color picture in the software, it should be (value + color) for one pixel. A raw data only have the value without color. So if you want to see colors with raw data, you should tell the software which rules the image using.
Thanks
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Re: ASI 178MC no color in ASCOM

Postby Pablo García » Mon Jan 08, 2018 2:29 pm

Thanks to everybody for your kindy comments, but I know the fonctionnement of the raw files, at least the DNG files from my DSLR. In fact I have my own program writed in VB6 for to debayerize the 16bit file, to stack and to stretch the image.

But for me, this is only a funny game, because I can use commercial or free apps doing the same actions and to obtein a JPG or TIFF 24bits RGB file at the end.

But, with the FITS files, I feel lost, because if I shoot a single file (16bit raw) from my new Zwo camera, I do'nt find any app capable of reading the file, debayerize, manage and save it as 24 bit RGB file. All apps that I tried, always show the picture as a bad B/W Image because it is visible the matrix pattern.

At the end, the question is easy. What app are you using to open a 16bit raw FITS file from a ASCOM driver color camera, debayerize, preview, manage and save ita as RGB file?

Regards

Pablo García
http://www.naturalezaycosmos.es
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Re: ASI 178MC no color in ASCOM

Postby chad » Tue Jan 09, 2018 1:52 am

Hi Pablo García,
I usually use MaxIm DL to open the FITs file.
And it also support the image processing.
Thanks
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Re: ASI 178MC no color in ASCOM

Postby MikeP » Tue Jan 09, 2018 5:15 pm

Hi Pablo,

If you are looking for a free program then you could try Siril if you are running a Mac or Fitswork for Windows as described here:

https://www.cloudynights.com/topic/544910-debayer-in-gimp/

If you are happy to pay and get more functionality then there are quite a few packages such as MaximDL, PixInsight, Astroart, Nebulosity, etc.

It's also worth noting that ASCOM has nothing to do with the FITS format. The ASCOM driver only returns the raw data from the sensor, it's the capture program which decides to store this data in the FITS format. For CCDs, FITS is pretty much standard as it ensures that you don't loose any data and also allows the storage of information in the keywords. As soon as you apply the de-bayer algorithm, data is lost so that's probably why most capture programs don't include this step (apart from a preview) and leave it up to you how you would like to apply it.

Mike
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