Problem with ASIFITSview image

[LaurenceT]

I had a session the other night imaging the Pleiades and have appeared to make a big error in reducing my 533MC Pro to zero gain. When I stack the resultant images in ASIdeepstack I get an image that I can possibly work with but when I open it in gimp or similar for stretching I get a different image that cannot be stretched.

I realise that I'm most likely not be able to do anything with my image but I'd be grateful if anyone can offer an expalnation.

 

[Elp]

I assume you've saved it as a tif before opening in GIMP as it cannot open fits files AFAIK. Have you also applied histogram stretches to the fits before saving to tif, otherwise the image will be very dark or near total black in most cases. GIMP will allow tif editing even on 32 bit files whereas some programs only allow 16 bit file editing.

[Varavall]

 

 

4 hours ago, LaurenceT said:

when I open it in gimp or similar for stretching I get a different image that cannot be stretched.

Hi

GIMP has a native FITS reader and I have no problems opening and stretching such files. Maybe you could post the stacked FITS file in questio

n here so we can see if I have the same problem or not. Then at least will will knw if its the file or your system that has a problem.

[LaurenceT]

On 03/02/2024 at 14:46, Varavall said:

 

 

Hi

GIMP has a native FITS reader and I have no problems opening and stretching such files. Maybe you could post the stacked FITS file in questio

n here so we can see if I have the same problem or not. Then at least will will knw if its the file or your system that has a problem.

Thanks for the offer but I can't upload an image no matter what I do so I'm abandoning this project for the sake of my sanity.

I'll try again next clear night with just an LP filter and unity gain.

[Varavall]

1 minute ago, LaurenceT said:

I'm abandoning this project for the sake of my sanity.

I think I lost mine long ago 🤪

Good luck with the next attempt.

[StevieDvd]

I've found that some programs will report the fits header of some ZWO files as 'file does conform to FITS standard' but will still load and allow stretching.

Have a go with Siril (as it's free) which may enable you to open the image and save in another format the Gimp supports.

[AstroMuni]

On 03/02/2024 at 10:00, LaurenceT said:

when I open it in gimp or similar for stretching I get a different image that cannot be stretched.

The possibility is - the view in ASIFitsview is showing an auto stretched view so when you open in Gimp its showing the linear view. i.e you would need to stretch quite a bit for the details to start showing up

If that isnt the case ....when you open a FITS file in Gimp it asks for a few parameters. Try setting Pixel value scaling as "By datamin/datamax" and Image composing to "NAXIS=3...."

Edited February 5 by AstroMuni

[LaurenceT]

57 minutes ago, AstroMuni said:

The possibility is - the view in ASIFitsview is showing an auto stretched view so when you open in Gimp its showing the linear view. i.e you would need to stretch quite a bit for the details to start showing up

If that isnt the case ....when you open a FITS file in Gimp it asks for a few parameters. Try setting Pixel value scaling as "By datamin/datamax" and Image composing to "NAXIS=3...."

Thanks for that, it makes sense that Asifitsview is stretching the image.

[PhilB61]

I can confirm that Asifitsview applies an auto stretch whenever you open a file, it can be turned off after hitting the histogram button. I would also recommend that you give SIRIL a try for both your stacking and processing that way you can do all in the same application, lots of tutorials online. I am a longtime GIMP user, but SIRIL has much better astro specific tools.

[LaurenceT]

5 hours ago, PhilB61 said:

I can confirm that Asifitsview applies an auto stretch whenever you open a file, it can be turned off after hitting the histogram button. I would also recommend that you give SIRIL a try for both your stacking and processing that way you can do all in the same application, lots of tutorials online. I am a longtime GIMP user, but SIRIL has much better astro specific tools.

Thanks, I've discovered that ASI Stack does indeed save an auto stretched file and I have done some minimal post processing. The blue nebulosity is almost absent and I cannot improve it, I'm wondering if this is due to my error in setting the camera gain at zero.

[ONIKKINEN]

OSC cameras, such as your 533MC produce a green tinted image because the camera is most sensitive to light at the green wavelengths and on top of that there are twice as many green pixels as there are blue and red ones.

You will need to colour calibrate the image to make the colours what they are meant to be.

[AstroMuni]

3 hours ago, LaurenceT said:

The blue nebulosity is almost absent and I cannot improve it, I'm wondering if this is due to my error in setting the camera gain at zero.

See if there is an option in ASI stack to disable stretching and save the stacked file. Get hold of Siril. It provides the tools to post process (you can also stack with it)

I have done a quick stretch on your image using Siril and you can see that there is nebulosity. So if you start fresh you should be able to get a lot more. Good luck

 

Edited February 6 by AstroMuni

[StevieDvd]

Can you drag & drop the fits file instead of the jpg file?

I have Siril so could correct the green tinge and run colour correction so you can see the result. If it's worth it to you then downloading and add Siril to your tools.

[LaurenceT]

2 hours ago, AstroMuni said:

See if there is an option in ASI stack to disable stretching and save the stacked file. Get hold of Siril. It provides the tools to post process (you can also stack with it)

I have done a quick stretch on your image using Siril and you can see that there is nebulosity. So if you start fresh you should be able to get a lot more. Good luck

 

There is an option to save a non stretched image. Thanks for doing that.

 

2 hours ago, StevieDvd said:

Can you drag & drop the fits file instead of the jpg file?

I have Siril so could correct the green tinge and run colour correction so you can see the result. If it's worth it to you then downloading and add Siril to your tools.

I can't seem to drop a fits file here, the system won't accept it.

I do have Siril installed, it's getting to grips with it is the problem!

Thanks for the replies.

[StevieDvd]

24 minutes ago, LaurenceT said:

I can't seem to drop a fits file here, the system won't accept it.

I do have Siril installed, it's getting to grips with it is the problem!

I can drop a fits file (drag & drop) or (Other Media) - don't know why you cannot!

Simple start for you with Siril:

• Open the file 
• Then in the Image Processing click on 'Remove Green Noise...' and just click on Apply.

Should fix your green tint in above image of Pleiades

 

Edited February 6 by StevieDvd

[LaurenceT]

12 minutes ago, StevieDvd said:

I can drop a fits file (drag & drop) or (Other Media) - don't know why you cannot!

Simple start for you with Siril:

• Open the file 
• Then in the Image Processing click on 'Remove Green Noise...' and just click on Apply.

Should fix your green tint in above image of Pleiades

 

Thanks, I'll keep trying to post a fits file.

[AstroMuni]

13 hours ago, LaurenceT said:

I do have Siril installed, it's getting to grips with it is the problem!

Follow the steps in this tutorial. As they have provided a link to the data files you can actually see if you get the results the author has got... https://siril.org/tutorials/tuto-scripts/

[alacant]

On 04/02/2024 at 18:34, LaurenceT said:

I'm abandoning this project for the sake of my sanity

For astro imaging, along with logical thought, any remaining sanity you may posses is a distinct disadvantage. 
 

[SteveNickolls]

Also try a gain of 100 with the 533MC and a wee offset (brightness) and see how you go. Much lower Read Noise and DR around 12-bits-

Cheers,
Steve