Lagoon - first step into processing

[beka]

Hi all,

To date I had been satisfied taking single shots with a DSLR and quickly seeing features of nebulae and fainter stars or moons of planets that I could not see at the eyepiece. Now I wanted to see what I could manage with further processing on a computer, so I took some pictures of M8 with a Canon EOS 700D on a NexStar SLT102 altazimuth refractor. I took about 20 30 second exposures at ISO 1600 and managed to get 6 with reasonably round stars. I then used Siril (because I have Linux on my computer and could not get DSS to run using Wine) to stack these after some issues. Siril appears to need to convert the input files to FITS format and also creates the final stacked image in this same format. It has features to then convert to others like JPEG but I found that the only way I could see the effect of the stacking was to open the final FITS file in KStars' viewer. I used the auto stretch feature of this viewer, then took a screen shot of that to which I applied a Gaussian blur filter  and scaled down in size with Gimp. I ended up with mixed feelings at the end of this foray. This work flow is definitely not ideal. The final result reveals more than a single shot from a technical point of view but I do not really like it aesthetically. If the reddish background "speckling" is part of the nebula I would appreciate any advice on how I can get a smoother appearance (or how to remove it if it is noise).

Cheers!

[Wiu-Wiu]

You should definately try the free trial of APP, Astro Pixel Processor. It works WONDERS for data like yours, and it gets even better if you add calibration frames. 

Very intuïtive, excellent results. There is a 'light pollution removal' tool, which will save your fine nebulousity and get rid of gradients and vignetting. 

Give it a go, you'll be amazed! 

[beka]

3 hours ago, Wiu-Wiu said:

You should definately try the free trial of APP, Astro Pixel Processor. It works WONDERS for data like yours, and it gets even better if you add calibration frames. 

Very intuïtive, excellent results. There is a 'light pollution removal' tool, which will save your fine nebulousity and get rid of gradients and vignetting. 

Give it a go, you'll be amazed! 

Thanks Wiu-Wiu, I just checked the site, i would try it but after your free trial the price is more than I would want to spend presently and the same for Pixinsight. Here is another attempt which I prefer to the first. This time I converted the raw too 16 bit png using Gimp then stacked with Siril, used Siril's auto stretch and exported to jpg. Finally tweaked brightness and contrast, cropped and scaled in Gimp.  I imagine taking darks and flats plus stacking more images would bring better results.

 

 

[lock042]

Siril can deal with your data with no problem. No need to buy any software ;).

With Siril you also have an autostretch mode. Then, of course you can process your images with the histogram transformation tool.

Take a look to the documentation, you could learn some interesting informations.

[beka]

... and one more, this time with master flat made by stacking 9 flat frames. This cleared the vignetting more noticeable in the original uncropped images. I also didn't scale down too much so that detail in the nebula is more easily visible. Did some fiddling with brightness/contrast and some blur in Gimp. I am wondering if some of the people that have posted outstanding images which took hours of exposure time and processing still have family and friends...

 

[lock042]

Hello.

You shoud use Siril color calibration tool on your image.

I've quickly done that with your jpg (in fact one never should apply this tool on non-linear image as jpg, but it was for the test).

Here the result:

[beka]

9 minutes ago, lock042 said:

Hello.

You shoud use Siril color calibration tool on your image.

I've quickly done that with your jpg (in fact one never should apply this tool on non-linear image as jpg, but it was for the test).

Here the result:

 

Thanks lock042 really much better. I am not sure if this is the place to bring it up - but when I converted the raw CH2 files in Siril (0.9.7 on Ubuntu 17.04) I got FITS files with only one channel (only luminance rather than the expected R, G and B). I had to convert to TIFF first before adding to Siril. I don't know if this a bug or if I have missed something.

[lock042]

Yes you got monochrome CFA pictures. Preprocessing must be done with CFA files. Not with interpolated TIFF files. 

[beka]

14 hours ago, lock042 said:

Yes you got monochrome CFA pictures. Preprocessing must be done with CFA files. Not with interpolated TIFF files. 

Okay thanks lock042, I think I will have to dig into the Siril documentation properly.

Cheers!