Undersampling is BAD!!.. Or is it?

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  • Опубликовано: 26 дек 2024

Комментарии • 81

  • @CuivTheLazyGeek
    @CuivTheLazyGeek  Год назад

    Support me on Patreon!: www.patreon.com/cuivlazygeek
    If you're planning on buying equipment, it will help me if you click the equipment links in the description first!
    Jeffrey Horne's Astrobin: www.astrobin.com/users/Jeffreyhorne/
    Previous video: ruclips.net/video/tzhpTDfJvo8/видео.html
    Dither and drizzle: ruclips.net/video/ItmrAZyLeek/видео.html
    M101 with details: ruclips.net/video/lFNyhrGYlVw/видео.html

  • @deep_space_dave
    @deep_space_dave Год назад +9

    Hi Cuiv! I watched your video on patreon but after watching it again here on RUclips, you are really speaking gold here as there are many out there who still do not understand these concepts. Your years of astrophotography experience shines here in this video and I hope many watch it several times to get a good understanding. Thanks and Clear Skies!

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад +2

      Thanks so much Dave! I love making these videos, and at the same time I'm kind of forced to because of the rainy season haha

  • @BelgianTex
    @BelgianTex Месяц назад

    Thank you very much for the clear explanations that even us newcomers can easily understand. Combined with your video "What camera and pixel size for YOUR scope?", this has been extremely helpful to determine my first DSO setup. Coming from wide angle nightscape Milky Way photography, I'm dipping my toes in the DSO waters to be able to have something to do during the winter months. These two videos have been extremely helpful in narrowing down the options.
    Next up: Watching your three hour long PixInSight class and supporting your patreon. 🙂
    Best wishes from a Belgian under the Dallas, TX light polluted skies.
    Merci beaucoup pour tous les videos!

  • @bbasiaga
    @bbasiaga Год назад +4

    Charles Bracken has a good discussion on why underampling is preferable to oversampling in his book on astro imaging. A good read. The whole book is in fact. Bottom line is don't sweat it, you are unlikely to be under sampled enough to matter with most scopes and modern cameras anyway. But it's easier to outrun your seeing with long focal length scopes and small pixel cameras if you are trying to get the maximum sampling your rig is theoretically capable of.

  • @ryanwood1911
    @ryanwood1911 Год назад +8

    Thanks, Cuiv, your videos on sampling have been awesome. The whole “undersampled = bad” advice always struck me as… oversimplifying things, is, I guess, a good way to put it. It always reminded me of when I was heavily into visual astronomy decades ago and the advice was “never have an exit pupil over 7mm because 7mm is the max size the human pupil can open, on average. Any larger exit pupil than your eye pupil is just wasting light.” But what they didn’t understand is that only children had 7mm pupils. The average adult only had a 5mm pupil, max. So if you lowered the power and the exit pupil became larger than 7mm, the image didn’t get brighter, but it also didn’t get dimmer, you just got more field of view. So if you need a wider field of view, just go for it!
    Sorry. I will get off my soap box now. That has been bugging me for 30 years. 😂

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад +1

      Hahaha yes on the exit pupil!! I think people want to be as efficient as possible, and sometimes forget about the big picture!

  • @nikaxstrophotography
    @nikaxstrophotography Год назад +2

    What I tend to do now is what you mentioned earlier especially with oversampling I shoot for the stars using a ircut or light pollution filter then expose for the nebula with a narrowband dual band as I only have an OSC camera, unfortunately I also have nothing but cloudy stars so have not really had much luck!

  • @JeffHorne
    @JeffHorne Год назад +1

    Another awesome video! And thanks for the shoutout! 🙂

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад

      Thanks Jeff - and your images are already so awesome they hardly need a shout-out :)

  • @davebillybish
    @davebillybish Год назад +1

    Hi Cuiv, super video thanks, though it raised a few concerns for me, especially when you said that x2 binning is practically useless in a cmos camera. I have recently got hold of an ASI294mm pro and one of the key features of the camera is it’s inherent two times binning that give it a large well depth and read noise as well. It is also ‘unlocked’ now and can be used in bin 1 mode, but at a cost to the well depth and read noise and High gain conversion ability in bin x2. I guess from what you say these binning capabilities are not as useful as the manufacture claims or hoped for?

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  10 месяцев назад +1

      Aha this is a great question! The 294MM as I understand has separate ADCs for the two binning modes, so it is a rare camera where binning actually does make sense! But it is unique for that model (and I may be wrong, having never owned it)

  • @rickbattle5706
    @rickbattle5706 Год назад +1

    Great video. Very informative. Clear explanation and easy to understand.

  • @kokoeblighatian3631
    @kokoeblighatian3631 Год назад

    One exception CMOS sensor (as far as I am aware) that can benefit from in-camera 2x2 binning is the IMX 492 (ASI294MM). That's because the sensor has 2 separate ADCs for each of the 1x1 & 2x2 binning modes.

  • @CraigStocksArts
    @CraigStocksArts Год назад

    Great explanation. One aspect I never see discussed is the effect of stacking. Averaging muliple observations will improve the estimate of the mean, so it seems that integrating multiple subs should improve the resolution over what’s available in a single image.

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад

      Stacking on its own doesn't really help (the better estimate of the mean is good for SNR though), but processes like drizzling make use of the partial pixel offsets afforded by dithering+star alignment to achieve what you're mentioning!

  • @PtiteSerra
    @PtiteSerra Год назад +1

    Hi, thanks for the video :) I did not quite get the part about well depth and read noise in the oversampling section of the video (and how they impact to the exposure time?), more research to do for me to better understand!

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад +1

      Yep, that's a different topic, I have an older video on that, but I might make an updated version soon!

  • @actudoran
    @actudoran Год назад +1

    i am typically oversampled with my 115/800 frac and the 585 sensor for my bortle 8-9 ... poor to ok seeing
    i recently have started to use Sharpcap and take advantage of lucky imaging. i still struggle to get a good enough balance between exposure length and all else ... i noticed that shorter exposures provide way more sharpness so bypassing the atmospheric wallowing and getting to FWHM of 2.1 which is real good! however it seems to always favour the brigher objects in the sky as it suffer at bringing out the fainter nebulosity....
    so i am considering a standard approach and stacking the Sharpcap image on top for more details within the core of the subjects

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад +1

      In Bortle 8-9 you should be overwhelming the read noise quite easily. Make sure your gain is high enough for your short exposures so your read noise is low compared to LP shot noise - it will then give you pretty much the same result as longer sub exposures (assuming same integration time)

  • @andrewweller5119
    @andrewweller5119 Год назад

    a really good video Cuiv. This is a topic that is confusing at first and you have broken it down very well.
    I have an Edge HD 11 @ 2800 FL and finding a camera that is perfect for that is a tall order. even with the .73 reducer it still comes in oversampled. Pixinsight has some good resampling options which help as my on camera (colour) binning never looks right.

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад +1

      Thanks so much Andrew!! I love these kinds of topics, making things easier to understand AND having practical use :) Glad you've got your workflow figured out!

  • @brinkoo7
    @brinkoo7 Год назад +1

    Great video! I have found that oversampling can get problematic with processing... the stars for example might be so large (9 HFR) that the software just does not want to detect them. Have you ran into this at all?

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад

      Ooooh no I haven't run into that - there are star scale detection settings that should help though!

  • @ChrisTurchin
    @ChrisTurchin Год назад +1

    Great vid, Cuiv. But I'll be honest, I'm just here for the pix-elles ... Clear ciels !

  • @stephenthexton7056
    @stephenthexton7056 Год назад

    Great video Cuiv, watched that through twice. Especially useful the bit about the binning. Like you I think some of my images are in both camps depending on which scope is being used. The tone of the video was really refreshing in that you are not doomed to failure, as some posts suggest, if you stray far from the path of ‘correct’ sampling. We all strive for the perfect image but I suggest more often than not it’s not the sampling being the major hurdle that’s holding us back😂 clear skies.

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад

      Thanks Stephen! And yes exactly! There is no one size fits all, we are all free to experiment!!

  • @stanmacdonald1073
    @stanmacdonald1073 Год назад

    Great video! The Hubble takes under-sampled imaged with yhe wide-field instruments. NASA developed the Drizzle or variable-pixel linear reconstruction algorithm to process the deep, wide field Hubble images. This process essentially paints a higher resolution image of the originals by drizzling "points" or "blobs" of light from the original images pixels to a higher resolution canvas. These blobs hit multiple pixels on the hi res canvas depending on the alignment of each original to the final canvas. If the originals were dithered then these blobs can add up statistically to create a new, higher resolution image. Phenomenal results can be obtained when dithering, drizzling and deconvolution are used together.

  • @DSOImager
    @DSOImager Год назад +1

    Good video. I tell people the suggested image scale range by a certain website is a guideline, not a hard set rule. :)

  • @richardheinsohn2624
    @richardheinsohn2624 Год назад

    Very good description between over and under sampling of images using long focal length scopes and wide field scopes with different cameras. I think you covered the topic very well.
    Clear Skies

  • @keithhanssen7413
    @keithhanssen7413 Год назад +2

    Did I miss something on mosaics? Is this a way to get wider field with acceptable sampling?

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад

      Yes, mosaics can of course achieve a wider FOV while still having all the details - I'm lazy though, so rather than do a mosaic (whose point is kind of look at an object as a whole), I'll rather use a very undersampled setup!

  • @jmm3194
    @jmm3194 Год назад

    Hi Cuiv, could you explain your statement "binning is basically useless" in CMOS??? Dont you improve your SNR by binning pixels? And also allows for adapting your (pseudo)pixel size to seeing, for example ?
    Great video again, thx

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад

      You can do the same thing more flexibly in post :)

  • @ldipenti
    @ldipenti Год назад +1

    I have a "properly sampled" setup (C8 SCT + 0.63x reducer + ASI533MC Pro) for OK to excellent seeing (as per astronomy tools website). What I have been reading on some forums is that if I debayer the images using "SuperPixel" (AFAICT, this method reduces the resolution of your images but is more correct as it doesn't do any pixel interpolation), I can take advantage of drizzling and get a better result that using VNG with no drizzling.
    Do you happen to have tried or read something about this? Right now I think there's a bug in WBPP that avoids this setup to be easily tested (when superpixel is selected, no matter which drizzle conf you ask, it'll default to 1x), but I guess it could be tried manually, I haven't yet.

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад +1

      I believe you could set debayer to bilinear, drizzling to 1 and square 0.9 and it would achieve this, if I recall correctly

  • @TheDJBozz
    @TheDJBozz Год назад

    Hi Cuiv, thanks fo another great video, I use an Altair 150mm f5 newtonian with an Altair Hypercam 183c fan cooled with 2.4m pixels, which is oversampled so I use 2x2 binning with sharp cap and get reasonable images with no loss of colour, my mount is an old eq5 so guiding is not great, I loose approx 30% of subs which can be frustrating, im in a Bortle 5 zone, so it is possible to run oversampled, I'm not a pixel peeper. 👍

  • @constellationshots3893
    @constellationshots3893 11 месяцев назад

    I was concerned abt this at the beginning, but then I pushed on with a asi1600mm and canon 50mm lens and since then, I’ve gotten really good images. I’m more so going for large regions of nebulosity (like cygnus or ifn bc that’s more so showing the scale than detail) because that’s what I like, even if I’m way undersampled.

  • @XxLukexX
    @XxLukexX Год назад +1

    Hey Cuiv, off topic but what do you think of the JTW Trident astrophotography mounts? Apparently there's a new GTR upcoming too with 30kg weight and can handle the same 75kg load as the P75 trident, no absolute encoder though like the P75 Trident has though.

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад +1

      On paper it looks amazing! But I haven't really seen any reviews...

  • @philippwagner1330
    @philippwagner1330 Год назад +1

    Hi Cuiv! I am quite new in astrophotography, about 3 months now.
    I have considered binning on my setup. Because i have 0,48 arcsec/px and I do unguided imaging with a TS RC8" on a IOptron HEM44EC.
    But I have not tried it yet, because i can get 2-3 minutes subs, depending on the polar alignment.
    I think I will try it, then I can get subs with even more than 3 minutes. What is your opinion on that ?
    Greetings from Austria and Clear Skies!

  • @4sapphireb
    @4sapphireb 2 месяца назад

    So binning for ccd and cmos mono and no for Osc?

  • @absorbingphotons
    @absorbingphotons Год назад

    Loved this video, Cuiv! I've always been a firm believer that undersampling is rarely ever an actual issue, and not nearly as bad as oversampling can be. Love the shoutout to Jeff Horne, too, his work is incredible!

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад

      Thank you so much! And yes, Jeff's work is absolutely mind blowing!

  • @astroshooter1960
    @astroshooter1960 Год назад

    Very good explanation, Cuiv 👍

  • @SKYST0RY
    @SKYST0RY Год назад +1

    Cuiv, I swear I think you were reading my search history yesterday as I was just looking up information on this topic. LOL🤣

  • @celestromel
    @celestromel Год назад

    Brilliant explanation - NOW I understand much more. My undersampling complex is now resolved. 😁 Thank you as always.

  • @40Sec
    @40Sec 10 месяцев назад

    I recently bought an asi553mc pro, and I'm struggling to decide on a main scope to use with it (currently I have a Skywatcher 72ed and Askar FMA 180). These are my two potential choices:
    Askar FRA300 @ 300mm focal length and F5
    Sharpstar 61 EDPH iii @ 270mm focal length and F4.4 w/reducer
    Not discussing any other elements of the scopes, but the FRA300 would give me a pixel scale of 2.575, and the 61 EDPH iii would be 2.86. This seems relatively close in my mind, but what are people's thoughts on how much different my results would be in terms of undersampling?

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  10 месяцев назад +1

      It's honestly not that huge of a difference, so with a 533 I'd go with the Sharpstar 61. Note that I will soon be testing and reviewing a small F6.3 scope from Founder Optics!

    • @40Sec
      @40Sec 10 месяцев назад

      @@CuivTheLazyGeek - Kind of the answer I was hoping for, as I hike all my gear around the city by bus/walking to get to darker locations since I don't have a car or backyard, and the Sharpstar is a couple pounds lighter even with the reducer. I think for my use case the faster optics may also end up being a bigger benefit than the higher end build quality of the Askar.
      Thanks for your feedback!

  • @mattlabrecque1265
    @mattlabrecque1265 Год назад

    So with undersampling. Can you just gather more data to make up for the lost details or go to a darker location? Or are they gone forever?

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад +1

      Nope, more data doesn't help -you'll only get better SNR, but never more resolution!

  • @efx245precor3
    @efx245precor3 Год назад

    Thanks for vid, I’ve been trying to understand this over the last few weeks.

  • @efx245precor3
    @efx245precor3 Год назад

    Best Astro tuber out there right now

  • @simonpepper5053
    @simonpepper5053 Год назад

    Great explanation Cuiv! I have always been aware of this and its never bothered me in the past, but I have always noticed when zooming in on my RedCat image being undersampled they do get blurry quickly. I am now drizzling which does improve things quite a lot. However I have another system that's properly sampled in good seeing and over sampled in poor my seeing its usually good so its definitely there of over sampled and the penny has dropped here when you said you can zoom in further as I captured just 3 hours on M51 and had to do a severe crop as I skipped the flats, but the details were so sharp even with minimal integration. I didn't put the two together here until now watching this so thanks! Here is my takeaway: Undersampled "typically" looks good zoomed out widefield images. Oversampled "typically" looks good zoomed in which I think is beneficial as you can then pick crops that others my not have tried! Thanks

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад

      Good takeaway, and glad the video help crystallize this knowledge you effectively already had!

  • @davidaucoin4990
    @davidaucoin4990 Год назад

    My head is spinning, but I grasped the comparisons of undersampling vs oversampling. I finally get it!

  • @anata5127
    @anata5127 Год назад

    I am huge fan of oversampling - 0.3-0.5”/pixel. Only seeing is limit.

  • @Phenolisothiocyanate
    @Phenolisothiocyanate Год назад

    If undersampling with the intention of dithering to drizzle the data I assume you have to increase your guiding accuracy. If undersampling at 1000mm and then doing a 2x drizzle you end up with an effective FL of 2000mm. Any errors in your tracking that were hidden in the undersampled data would be revealed.

  • @brokenigmatic
    @brokenigmatic Год назад

    My astro camera has tiny 2.4µm pixels and I've been oversampling on everything except my widefield setup. 😅 What a headache of a way to begin the hobby!

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад +1

      Hahaha you're starting the hard way for sure :)

  • @frankm81m82
    @frankm81m82 Год назад

    Great video!

  • @efx245precor3
    @efx245precor3 Год назад

    Sounds like dithering is a good idea

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад

      Dithering is ALWAYS a good idea :) I see it as compulsory if the equipment is capable of it!

  • @sorcio46
    @sorcio46 Год назад +1

    Rule of thumb in digital signal processing (in general): it's way better to do undersampling rather than oversampling.

  • @Mrpaulgs
    @Mrpaulgs Год назад

    I am not stupid (ok maybe I am it's hard to be objective about your own intelligence}, I have an engineering degree, this still sounds like word salad to me. I wish I could find an understandable explanation of over sample and under sample.

    • @CuivTheLazyGeek
      @CuivTheLazyGeek  Год назад +1

      As mentioned the real explanation is in the previous video :)

    • @Mrpaulgs
      @Mrpaulgs Год назад

      @@CuivTheLazyGeek I will go back and watch it again.