Astrophotography - Is it worth it to stack and process multiples than taking a single exposure?

Updated: Apr 16, 2018


It’s more work and it takes more effort, but in the end the image quality you get from stacking multiple exposures is a huge improvement to your final product in multiple ways.

Reduce noise

Stacking multiple exposures reduces noise by increasing the signal. It’s pretty simple — signal is the stuff (light) we want, noise is the stuff (camera sensor errata) we don’t want. One of the best benefits about stacking multiple exposures is the dramatic increase in the image quality, noise removal, by increasing your signal to noise ratio.

When you stack, you reduce the differences in the digital representation of the light that hits and excites the camera sensor. Each time you shoot an image, the electrical characteristics of the sensor cause it to do its best at representing the photons it “sees.” However, from shot to shot, there are slight brightness and colour variations on each pixel for the exact same image. Image stacking produces an intelligent average of each pixel of all exposures, detail for detail, instead of trusting just one exposure and hoping it’s accurate.

Along with decreasing noise — you are also able to saturate your images to get more accurate colour because you are boosting  signal instead of boosting the noise.

I’ll let you compare for yourself. Below you can see an example of a single 18-second (top image) Milky Way image, followed by a stack of 5 different exposures (18-seconds each). Both were post-processed a little differently from the same raw images, but after stacking, there was lot more data to work with.

How you do it

There are a few good software packages out there. Some are free, some are not.

I’d highly recommend PixInsight, but isn’t free and it has a big learning curve. So, if you’re just starting out — give Deep Sky Stacker a try. It’s free and easy to use, and works pretty well, too. Once you have a TIFF image from your stacking in DSS, you can edit it with your favourite image processing application and tweak to your heart’s content.

To learn more about this, checkout out workshops held every month in Brisbane, Ipswich and the Scenic Rim -

#astrophotography #photographyworkshops #milkyway

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