Is this stack from DSS too bright?

[feverdreamer1]

 

 

 

 

 

Some background, as you can see, it's the orion nebula and neighbourhood.

This was shot last night at ISO 1600 canon 550d. With a CZJ 135mm stopped at f3.5 I believe. (first light with this lens by the way). 

There are 58 frames at 50 seconds each, after discarding about 30. I also took 10 bias and only 15 darks because my camera died :(.

Is this image too bright? Should I process it or did I mess up some DSS setting. I used Kappa sigma clipping and abour 54% treshold.

 

Thanks and clear skies!

 

 

[AstroNebulee]

Try processing it and see what you get, nothing to lose there, great start 👍

[vlaiv]

It is normal to have high background levels if you shoot in light pollution and have faster lens.

This is always dealt with in post processing.

54% is too aggressive setting for Kappa Sigma clip. Set it to reject top 5% or so of samples - sigma of 2 will give you 95% accepted and sigma of 3 will give you 99.7% samples accepted.

[feverdreamer1]

16 minutes ago, LeeHore7 said:

Try processing it and see what you get, nothing to lose there, great start 👍

Will do for sure, that stacking time won't be wasted  

[feverdreamer1]

6 minutes ago, vlaiv said:

It is normal to have high background levels if you shoot in light pollution and have faster lens.

This is always dealt with in post processing.

54% is too aggressive setting for Kappa Sigma clip. Set it to reject top 5% or so of samples - sigma of 2 will give you 95% accepted and sigma of 3 will give you 99.7% samples accepted.

Okay, almost thought I had wasted another night. Thanks, I will try what you say.

[feverdreamer1]

This is the tiff (16bit/ch) file:

https://drive.google.com/file/d/1sm-_MVfILDNd9aMexPY5KDnjoepCaOZ8/view?usp=sharing

[vlaiv]

1 hour ago, feverdreamer1 said:

This is the tiff (16bit/ch) file:

https://drive.google.com/file/d/1sm-_MVfILDNd9aMexPY5KDnjoepCaOZ8/view?usp=sharing

Well, it is very decent recording

I had to jump thru a lot of hoops to get this level of detail, but I think it is worth it.

Flat calibration was not performed - there is a lot of vignetting and there is also some LP gradient in the image. Quite challenging processing to be honest.

Here is result:

I think that you should be pleased with this - you captured great nebula of orion, running man, horse head and flame in one frame!.

[feverdreamer1]

2 minutes ago, vlaiv said:

Well, it is very decent recording

I had to jump thru a lot of hoops to get this level of detail, but I think it is worth it.

Flat calibration was not performed - there is a lot of vignetting and there is also some LP gradient in the image. Quite challenging processing to be honest.

Here is result:

I think that you should be pleased with this - you captured great nebula of orion, running man, horse head and flame in one frame!.

Thanks Vlaiv, that's a great image. I didnt do flats, but I plan on learning how to do them soon. 

May I ask how and where did you process it? Thanks again and clear skies,

S

[vlaiv]

3 minutes ago, feverdreamer1 said:

May I ask how and where did you process it? Thanks again and clear skies,

Sure. I loaded the Tiff in Gimp 2.10 and then I split channels - red, green and blue into separate monochromatic images and saved them as fits files.

Then I loaded each of them in ImageJ. I binned them 3x3 to improve the SNR and then I did synthetic flat fielding.

I inspect image and find max pixel value that saturates targets but does not saturate background. Then I run macro to remove all the pixels with higher value in the image (this sort of leaves only background). I then run another command that fills in missing pixels by taking average of existing pixels around them (sort of mean filter that only looks at actual pixels and not missing values).

In the end, I do low pass filter with Fourier transform to remove fine detail / noise and leave "smooth" background. I divide each channel with respective background.

Then I run gradient removal plugin that I wrote on each channel and save them all.

I then loaded each channel in Gimp and did channel combine to get RGB image back again and did basic 3 point levels stretch (move top slider until nebulosity is about to saturate - move middle slider to properly expose everything and move bottom slider to remove background offset).

That is it. Most of the work is done in ImageJ - but after flat field is applied and gradient removed - data is really nice to work with.

[feverdreamer1]

11 minutes ago, vlaiv said:

Sure. I loaded the Tiff in Gimp 2.10 and then I split channels - red, green and blue into separate monochromatic images and saved them as fits files.

Then I loaded each of them in ImageJ. I binned them 3x3 to improve the SNR and then I did synthetic flat fielding.

I inspect image and find max pixel value that saturates targets but does not saturate background. Then I run macro to remove all the pixels with higher value in the image (this sort of leaves only background). I then run another command that fills in missing pixels by taking average of existing pixels around them (sort of mean filter that only looks at actual pixels and not missing values).

In the end, I do low pass filter with Fourier transform to remove fine detail / noise and leave "smooth" background. I divide each channel with respective background.

Then I run gradient removal plugin that I wrote on each channel and save them all.

I then loaded each channel in Gimp and did channel combine to get RGB image back again and did basic 3 point levels stretch (move top slider until nebulosity is about to saturate - move middle slider to properly expose everything and move bottom slider to remove background offset).

That is it. Most of the work is done in ImageJ - but after flat field is applied and gradient removed - data is really nice to work with.

Thanks Vlaiv, for such a detailed and well explained message. Is imageJ easy to learn? I'm still getting used to GIMP and am now starting to properly use StarTools.

[vlaiv]

1 hour ago, feverdreamer1 said:

Thanks Vlaiv, for such a detailed and well explained message. Is imageJ easy to learn? I'm still getting used to GIMP and am now starting to properly use StarTools.

It is open source and free. It's used for scientific image analysis (mostly microscopy) but it has all the right tools. It's not hard to learn, but most of operations are fairly generic - you need to understand image processing quite well to accomplish what would otherwise be simple "filter" in photoshop or similar.

[feverdreamer1]

9 minutes ago, vlaiv said:

It is open source and free. It's used for scientific image analysis (mostly microscopy) but it has all the right tools. It's not hard to learn, but most of operations are fairly generic - you need to understand image processing quite well to accomplish what would otherwise be simple "filter" in photoshop or similar.

Hmm I see, will stick to what I'm using for now, and try to "master" that before jumping to other software,

Thanks and have a good one,

S

[CraigT82]

22 minutes ago, vlaiv said:

It is open source and free. It's used for scientific image analysis (mostly microscopy) but it has all the right tools. It's not hard to learn, but most of operations are fairly generic - you need to understand image processing quite well to accomplish what would otherwise be simple "filter" in photoshop or similar.

Why imageJ and not AstroImageJ??

[vlaiv]

Just now, CraigT82 said:

Why imageJ and not AstroImageJ??

To be honest - Fiji (Fiji Is Just ImageJ - recursive acronym)

AstroImageJ is quite modified and geared towards measurement of astronomical data - photometry, astrometry and such.

ImageJ is just basic package with basic functions, while Fiji is distribution loaded with various useful plugins.