Am I able to stack jpeg and raw files together

[Scribblecrans]

I accidentally shot about 45 minutes of data in jpeg before realizing that I shot in the wrong mode. Unless someone tells me otherwise I am just going to take the jpegs out of the stack but it would be nice to have if they could in some way help.

[teoria_del_big_bang]

Oh dear, these things happen 🙂 

I guess it might depend on what software you are using to align and stack the images.
I think in Pixinsight you can stack fits and jpg images together.

However, personally although this has never happened to me I don't think would use them even if you can.
The reason is that there is probably very little signal stored in a jpeg compared to raw data and also when stacked you might loose any information stored in the fits headers which can often be useful to processing software.

I could be wrong but below are the same images one saved as a fits (left) and the other a JPG saved at 100% quality (right)

Both look the same.
But when I apply the same stretch to both images

Now all the data in the fits image is released but in the jpeg there is nothing worth using.
Whether a jpeg from a DSLR or other camera only has the same data in there I am not sure but I suspect it would be the case.

Steve

[vlaiv]

No, no, no!

Jpeg data is completely useless.

Format uses 8bit data which clips away most of faint signal that is very important and on top of that - it adds compression algorithm artifacts.

Jpeg was developed to alter image in visually acceptable way so that it compressed better. This alteration of data makes stacking useless as stacking expects "natural" noise and signal distribution in order to work properly.

[Xilman]

On 08/06/2022 at 10:26, vlaiv said:

No, no, no!

Jpeg data is completely useless.

Format uses 8bit data which clips away most of faint signal that is very important and on top of that - it adds compression algorithm artifacts.

Jpeg was developed to alter image in visually acceptable way so that it compressed better. This alteration of data makes stacking useless as stacking expects "natural" noise and signal distribution in order to work properly.

I would phrase that as "mostly useless".

Completely useless for making a pretty picture and for the reasons given.

Jpeg may clip away some of the faint signal but not always all, especially if the dynamic range in the image is limited. Consequently, stacking will add that small signal and improve the SNR.

The result may be perfectly useful for astrometry of faint objects, asteroids or instance, or for bare detection of very faint objects. The latter can indicate whether an eruptive variable, nova, supernova, etc was above a limiting magnitude at the time of observation. Such detections can be scientifically valuable.

[Clarkey]

On 08/06/2022 at 08:06, Scribblecrans said:

I accidentally shot about 45 minutes of data in jpeg before realizing that I shot in the wrong mode.

That's nothing. I did a whole night of luminance data using a blue filter.🤪

Cut your losses and use good data.

[Xilman]

1 minute ago, Clarkey said:

That's nothing. I did a whole night of luminance data using a blue filter.🤪

Cut your losses and use good data.

Nothing is ever completely useless. If nothing else, it can serve as an awful warning.

In the case in question, I would check to see what else may be in the field. You never know --- you might have a nice image of a passing asteroid.

I never throw away potentially useful data. Even if they are not useful for the intended purpose they may be useful for something else in the future. Storage is cheap.

 

[Clarkey]

3 minutes ago, Xilman said:

I never throw away potentially useful data. Even if they are not useful for the intended purpose they may be useful for something else in the future. Storage is cheap.

I did not throw it away - but my LRGB image had a very good blue channel!