The Drizzle, an algorithm designed for Deep Space

This feature is present in the main Astrophotography processing softwares longer in use, and to be clear, the commercials “Nebulosity” and “PixInsight” and freeware and “Deepskystacker“.

What makes it special is the ability to get enlargements of the area photographed, with greater definition, without compromising it with additional noise as would happen oversampleing a 200% crop, and in some cases also allows you to get more signal/detail in that area.

Taking a cue from what little I’ve found on the internet about the Drizzle, this is the function that takes advantage of the algorithm called “The Variable-Pixel Linear Reconstruction” which was originally developed at the Space Telescope Science Institute to process Deep Field images from the Hubble Space Telescope.

Drizzle is a linear algorithm for reconstruction of downsampled images from dithering (*), basically allows you to work in pixel mode doubling the size of each image (triples if you choose the drizzle 3 x).

To take effect, the Drizzle, you must have raw data that have these requirements: Downsampled images: If the images are already well sampled, the Drizzle won’t give you great benefit. Images with Dithering: Drizzle is absolutely necessary and without proper dithering the rebuilding process is not working. Many images: Drizzle requires more images than a handful of images that a wide field astrophotography. The more the better, but generally you should acquire at least 20/30 images to get good results.

[ *  -For dithering applied in astrophotography, also as a function of driving software, means that every single shot has the exact same field resumed (FOV), but always present a small shift, a drift that then generates the final image darker sides those borders. See also:

We could call it vulgarly a crop more powerful, but also a little as if the photo shooting increased three times without carrying those annoying aberrations than a “teleconverter” optic, although of excellent brand you would bring back.

A little like giving hormones to the telescope:) or one of his “second life” warning though, this type of processing actually produces the benefits in the image only if it was taken with perfection to the native focal, I mean focusing great Chase very good, otherwise the image produced in drizzle also amplifies these faults!

This is the pubblication of Space Telescope Science Institute about Drizzle:

Click to access 9808087.pdf


And here are some examples to better understand what we’re talking about, before without drizzle to campio full (APS-C) and then Drizzle 2 x:

M51-Whirlpool Galaxy-Celestron optics C11 xlt block mirror mod. f/10 @ f/7 (2200 mm focal length)
The same stack processed in drizzle 2 x
NGC7293-Helix Nebula-with a 130 Super Apo Triplet f/7 mm (focal 910mm)
The same stack processed in drizzle 2 x

To learn this technique of elaboration, I suggest you my TUTORIAL “Deepskystacker e Drizzle Function”:

Tutorial: Deepsky Stacker (DSS) and Drizzle function

Thanks for viewing and bye 🙂


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