Demystifying Drizzle in Astrophotography
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- Опубликовано: 10 фев 2025
- Drizzle is quite a complex topic - so I break it down for you in what drizzle is, why and when to do it and how to apply it in AstroPixelProcessor and PixInsight.
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Thanks for this excellent in-depth explanation and partial workflow example, it's taught me a lot!👍
Hi Sacha,
Nice video! Should you also mention the requirement to dither with a sufficient imaging camera pixels (for instance at least 20 pixels on the imaging cam)? And also to dither with a non-integer pixel value on the imaging cam (we should target a pixel value for the imaging cam with some decimals)? NINA (in nightly version) has the ability to show you the number of imaging pixels you dither when you set your guiding cam dither pixels.
Keep it up with your very interesting videos! Merci vielmal
Very interesting and valuable comment!!!! And so we learn from each other!!!!!
@@viewintospace My pleasure! I've already learned so much from you...
And how often should you dither? I recall Quiv once mentioning you should dither every picture. Any ideas on that?
@@tvanpeer I would support that statement from Cuiv. If the minimum requirement is 30-50 pics then it means so many pics with different positions - so except you make 1000s of shot exposure pics, you should dither every time!
@@viewintospace And for OSC with scale 1?
Hi Sascha another nice explanation thanks! I'd like to clear up a little nit-pick of misinformation though.
In 1978 as an astrophysics undergraduate, I attended an extra-curricular lecture at the Royal Observatory Edinburgh about the (then novel) development and application of CCD arrays. Up to that point I'd been using a single CCD cooled to -40C on a 20" Cassegrain to measure light curves of variable stars. After the lecture I asked a question about "moving the array and interpolating the signals between the pixels". The prospect of mechanically and mathematically doubling that scale (with what we now call dither and x2 drizzle) that I didn't want to be overlooked. But the lecture team immediately recognized this concept, were already fully aware of these possibilities, even before the technology had reached 8x8 scale.
So *full credit* to the Hubble team for the development and application of an early implementation, and for influencing the terminology we use today. But despite their high public profile, its wrong to say that they *invented* it. This idea was already a more than decade old. It took that long for the sensor arrays to catch-up and make it worth doing and american $$ to put it into space. To be honest, the idea was obvious to any young student in the 1970's who listened attently to an hour of discussion about using ccd arrays. Of course every country claims they invented everything, but more people should realise that Scotland actually did 🤣.
Thanks a lot - great story!!!!!
After watching this I'm noticing that my drizzled stacks are dimmer and harder to stretch than non-drizzled. For Christmas Tree Nebula with around 60 x 300s I abandoned the drizzled image in order to get enough saturation on the starless part of the image. Even with Jelly Fish at 111 x 300s I find the starless to be very weak for stretching in GHS. And these are with a drop size of 1, not 0.8.
A great tutorial on a process I didn't understand before. Thank you Sascha.
Finally I understand what this drizzling thing is all about with a very clear explanation. Thanks for this extremely useful tutorial.
Nice timing with siril now featuring true drizzle as well exactly today!
Excellent tutorial. I was never sure how much scaling (drop shrink ) to use. You have now given me a good starting point. Thank you, Sascha for clearly explaining the theory and process 👍
Excellent tutorial. I've always assumed it was a complex subject so I've never used drizzling. But even through you tube compression it's obvious how much sharper the images are and the value of drizzling. I always dither for noise reduction so I'll definitely enable drizzling when I do my stacking in astro pixel processor. Many thanks for sharing 👍
Fantastic video. Thank you!
Great explanation. New subscriber earned!
Just found your channel. Thanks for making these tutorials! ❤
Should you click "apply to all groups" in WBPP?
Now I get the difference between the bayer trans drizzle and the normal drizzle, it is for the colour/greyscale so when I split the channels in APP I use just drizzle for HA and O3 and bayer drizzle for the Colour version, this explains why I get the crosshatch pattern when bayer drizzling.
Great video Sascha. I have a Redcat 61 and ASI533 mc pro. The red lines in the graphic disappear with drizzle 2x, the red figures disappear at drizzle 3x. What is wise? 2x or 3x? Thanks
Stay with 2x, Only if you would be still substancially oversampled 3x would be justified.
Hello one quick question, did you process the actual X2 drizzled image or do you resample by 50%. The image with 100% is so large that my BXT takes forever
I do not resample - I like to have as much resolution as possible. With my M2 Mac BXT is blazing fast, however bit the pic is.
I typically dither at every 3 subs and a 5 pixel movement. Is that enough if I am gathering say 100 to 200 subs? Going to dithering every sub would add a bunch of time to my imaging session. How often should you dither to support drizzling? Love your tutorials. You do a great job.
If you plan to shoot a 100 subs, I would dither every 2nd sub to reach the 50 dither movements... and so on....
As always with your videos it's nice to get hard numbers; I've been setting drop shrink to 1, so may need to go back and reprocess. My workflow has gravitated to WBPP with drizzle 2x, GraXpert, BXT, then resample back to the original resolution. Is that what you do?
I never resample back, always happy to have some extra resolution 😉
I always BIN x2 to make my scope under sampled to collect light faster then drizzle but i use a momo ccd not cmos
Hi, nice comprehensive video on the topic. I have a question: you mentioned dithering and number of images as mandatory requirements for drizzle. I usually collect many frames (over several sessions, so with potentially somewhat variable seeing); but I dither every two frames. Is this okay or do I have to dither frame by frame?
Thank you.
Also I had forgotten a second question: you mentioned deconvolution as another important ingredient to get a good picture with drizzle. But you didn't explain more in details, then I assume that just after image integration (with drizzle active) I should immediately apply the deconv. before start processing my mono images. Am I right ?
That is fine as long as you have a large amount of total exposures.
No, deconvolution in our days means BXT (BlurXTerminator). Just use it when it is it's time in the process. You might look at my 10 Golden Rules video for reference to which process should be used in what sequence.
Juan from PI says you should dither (1x) even if you don't dither.
Yes, for SPCC is is required
Is there an online to calculate if im over or undersampled?
The MTF tool I demonstrated is online - link in the description
@@viewintospace still watching, sorry and ty
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