Astrophotography: How to dither and do it right

A.V.Astronomy

Подписаться 8 тыс.

Просмотров 20 тыс.

50% 1

This video really covers in detail what goes into setting up dithering properly in your image sessions. We cover image scale and dither scale along with some basic calculations so you can maximize the noise reduction SNR improving benefits of dithering.
My Link Tree - linktr.ee/avastronomy
Links to my other videos that explain layer masks, camera settings, Collimation and image processing in more detail.
• How to process Astroph...
HLVG - www.deepskycolors.com/archive...
Gradient Xterminator - www.rc-astro.com/resources/Gr...
OPT telescopes and Agena Astro have a tremendous inventory of astrophotography gear and great service. You can check them out here through my affiliate links. This is the setup I currently use.
Agena Astro - bit.ly/3D3U8id
ASI AIR PLUS - bit.ly/46BTfej
IOPTRON GEM 28 MOUNT - bit.ly/3O2QpGX
WILLIAM OPTICS Z61 - bit.ly/44v5Hv7
IOPTRON IGUIDER - bit.ly/44AXRzv
ASI 294MM CAMERA KIT - bit.ly/46Clqd3
Links to helpful astrophotography items that can be purchased directly through Agena Astro.
TELESCOPES
Redcat71 APO telescope - bit.ly/3D6cT4s
Sky Watcher 8" Dobsonian reflector telescope - bit.ly/3XGYwNy
ASTRONOMY CAMERAS
QHY 600M - bit.ly/3rbHgno
ZWO ASI533MC Pro OSC camera - bit.ly/3XPlzpx
ZWO ASI2600MC pro camera - bit.ly/3pDJFHg
MOUNTS
ZWO AM5 Mount - bit.ly/44eHUzn
Sky Watcher Star Adventurer 2i Pro pack - bit.ly/44gXXMV
Sky Watcher EQ6 R pro mount - bit.ly/3riYbVc
Sky Watcher EQ8 (for heavier payloads) mount - bit.ly/3D3UFkd
Celestron CGXL mount - bit.ly/3O2u6lQ
FILTERS
Optolong Luminance Pro (broadband light pollution filter) - bit.ly/46FIdEJ
Optolong L-extreme(vary tight/narrow dual band light pollution filter) - bit.ly/3NLwrjJ
Optolong L Ultimate - bit.ly/3NIHABV

Опубликовано:

7 июл 2024

Ссылка:

Скачать:

Готовим ссылку...

Добавить в:

Мой плейлист

Посмотреть позже

Комментарии : 112

@5teveL1 3 года назад

Thanks for this, I thought I had set my dithering up correctly but had the same noise as you, even with a lot of subs. I have now adjusted so I will be trying this out next session.

@itaialter 3 года назад

I recently started to do manual dithering with my Skyguider Pro (I bought a smoother DEC panning head for that). Every 3 frames I lightly press the RA direction button and carefully move the DEC panning head. It fixed my 'walking noise' issues and improved the overall quality of my images.

@AVAstronomy 3 года назад

itai alter that’s a solid method for sure. Clear skies and thanks for watching!

@nxu5107 2 года назад

Crikey you are so brave to touch the head while you are capturing stuff. Glad it works. I think you need to do a video on you technique! thanks a lot. I use a non guiding astrotrac and have never been able to get my head round PHD. dont know why. So grat stuff.

@renannegresiolo220 3 года назад

I’ve learned a lot from you, thank you. Greetings from Brazil!

@rowdymrb2358 3 года назад

I did this last night before my meridian flip went haywire. Will continue imaging with this method tomorrow and cannot wait to see the results.

@AVAstronomy 3 года назад

That’s awesome. Thanks for watching!

@JZHGaming 3 года назад

I am about to start attempting to guide and dither this week, this video helped immensely!

@AVAstronomy 3 года назад

Awesome! Good luck with your session!

@JZHGaming 3 года назад

@@AVAstronomy thanks!!

@dilipsharan8699 3 года назад

Great video. Thanks for sharing

@jesuschrist2284 3 месяца назад

Ty so much this got jy guide scope and cam today

@rubenherrera6185 Год назад

Gracias ,Excelente explicación.

@Nottsboy24 3 года назад

Nice upload 👌🔭

@AVAstronomy 3 года назад

Notts boy24 thank you sir!

@lightningclips18 3 года назад

Nice video 🔭

@nxu5107 2 года назад

Also I am so glad you only use a DSLR on this. I have two 550d and 6d. Ithink I will stick with them and I use old M42 tamron lenses. This gives me some hope that I can get some stuff done once I am out of isolation. Hmmmmm. just looking forward to this now.

@adityakarade8034 Год назад

Thank you sir for great video yesterday I have capture rho Ophiuchi but i haven’t dither the image and the target was fixed in frame and not moving anywhere now I know importance of dithering my undithered image turn really horrible and next time I will not make mistake I have Wi-Fi version of Sky-Watcher 2i so I can set dithering number in app and thanks for your video clear up my doubts

@louisrosner7902 3 года назад

Great video. One thing Id add is that if you dither you can drizzle when you stack. Much better resolution although the file size becomes incredible. I’ve been correcting by just changing the image size in Photoshop so I have smaller files to work with.

@TheHeldere 3 года назад

Hellom you drizzle on 2x or in 3x ?

@louisrosner7902 3 года назад

Helder Grincho Drizle 2x

@AVAstronomy 3 года назад

Hi Louis, Drizzle is a great technique I use as well to recover some resolution but as you said the file sizes can be huge so I limit to 2x drizzle when I use it. Clear skies!

@AstroNightBR 3 года назад

Very good👏👏👏👏

@AVAstronomy 3 года назад

Desvendando os Fatos thank you!!

@dankahraman354 3 года назад

Dither level versus dither scale..what is the difference...? I will look it up

@TheHeldere 3 года назад

Tonight i Will try to use your tutorial. ONLY in RA, i have One SW star adventurer. Thanks

@TheHeldere 3 года назад

I' had folowed your tutorial and the web page www.myastroscience.com, and it work very nice. :)

@AVAstronomy 3 года назад

Glad to hear it worked out for you. Thats great! Clear skies and God Bless!

@JoeBob79569 4 месяца назад

Yea, it just dawned on me recently after setting up my new scope, and getting everything working again, that my guiding errors were actually a lot larger than my dithering, and I realised I couldn't even see the dithering on PHD2 because the value was so small, and it was one of those "light bulb" moments that I was slapping myself because I didn't see it sooner! But granted I was also "chasing the seeing" at the time so even if my dithering was correctly set, my guiding errors would probably still have been worse than my dithering anyway! 🤣 Astrophotography can make you feel really stupid sometimes..

@AstroPixUK 3 года назад

Great video again Aaron. Wish I hadn’t got 3 scope and 3 combinations of camera to work out.... haha

@AVAstronomy 3 года назад

😆. If you need help figuring out which camera pairs best with which scope, let me now and I’ll give you my 2 cents worth. 👍

@AstroPixUK 3 года назад

A.V.Astronomy I’ll message you via Instagram the weekend. Thanks Aaron.

@aldenamparo1776 Год назад

Where do you get 1280x760 pixel size? Try to look in camera specs but its quite confusing.

@JZHGaming 3 года назад

I finally tried guiding and dithering last night! I think it went okay once I finally got everything kinda of figured out. Couple of questions - I don't have a cable to hook my Sky-Watcher EQ6-R Pro to the PC so I am using the ST-4 connection from the camera. I finally got PHD2 to accept the dithering command from ATP (it would just pause guiding - changed port from 4300 to 4400 in ATP). Took me about 3 hours to get it to work from there but it always waited until dithering time out in ATP before making the next exposure. Any tips on dithering / guiding using the ST-4 connection?

@AVAstronomy 3 года назад

I’ve not used ST4 as pulse guiding is superior to it. You really need to get the EQDIR cable from shoestring astronomy. It plugs directly into the mounts remote control port amd you pc. That’s the way to go. 👍

@JZHGaming 3 года назад

@@AVAstronomy yeah, my SW EQ6-R has the USB B port as well, so I have a cable coming in for that (as well as a USB hub since I don't have enough USB ports!) I am pretty confident everything worked - was able to take 14 subs of 180s of Andromeda at 400 ISO and noise was a lot lower and no trailing.

@piccolodiavlo 3 года назад

Really great vid. When I run through the calculations i get 30/2.91 = 10.3. If I'm going with ten does APT take the 5 and PHD the 2? or vice versa? noise is a thing i need to reduce lol. Thanks again... J

@AVAstronomy 3 года назад

Yes, you can put APT at 5 and PHD at 2. That’s the way I do it and I get awesome results from it. 👍

@astroimager3010 3 года назад

What is your settle time after dithering?

@AVAstronomy 3 года назад

I do 15 seconds usually.

@ElGronto 3 года назад

Great video! So do you dither after every frame?

@AVAstronomy 3 года назад

El Gronto you certainly can but I find that every other frame works just as good and it will maximize your imaging time. Thank you!

@chitownxring1444 3 года назад

What is the Pixel scale for a Canon 3Ti (crop sensor) on a Celestron 8SE 2032 FL with a FR of 0.75 giving me a FL of 1524 using a OAG with ASI120MM?

@AVAstronomy 3 года назад

The pixel scale of your imaging camera and celestron 8se = .6, the pixel scale of the ASI 120mm using an OAG is .52, so what you do is divide .52/.6 = .867, to move 30 pixels in your dither you calculate the following. 30/.867 = 34.6. You'll need to max out your dither movement in PHD2 and APT if those are the programs you use. this means setting dither scale in APT to 5 and setting it to 7 in PHD (7x5=35 which is right around your target of 34.6) Hope that made sense, but if not at least you know the settings to use now for that scope and camera combo. good luck and clear skies!

@chitownxring1444 3 года назад

@@AVAstronomy Thanks for the quick reply... Also looking at APT v3.87 which is what I am running, when I click on Dithering Distance: I see that it goes from 1-20 then it keeps going in increments of 10 all the way to 90. Sure would have been nice if it continued in increments of 5. I guess I will go with 7X5 unless you feel there is a better way. Edit: Which parameter do I change to 7 in PHd?

@AVAstronomy 3 года назад

@@chitownxring1444 must be a new feature of version 3.87. I currently use 3.84. sounds like I need to upgrade. Even so, the formula stays the same. You still need to shoot for a total of 35. So if you APT to 5 and phd to 7 or APT to 7 and PHD2 to 5, the results should be the same.

@skuda13569 3 года назад

Sake man I had to skip 4 ads before I could watch this video, I know what your doing youtube, you'll never get my money!!!

@AVAstronomy 3 года назад

Sorry about that man. Unfortunately I don’t control how many ads per ad section it will play. It’s auto generated.

@skuda13569 3 года назад

@@AVAstronomy haha I know, cool video by the way, I'm just learning about dithering, see if it's something I should be doing, I'm fresh to the game, so at the moment it's just me my scope and a dslr

@AVAstronomy 3 года назад

@@skuda13569 some people will tell you it’s not necessary. It will massively reduce the amount of noise in your images, especially if you dither every frame, but every other frame is good too.

@nxu5107 2 года назад

Thanks for this video. You know what this stuff sound like? It's heavy metal or beyond. I am just isolatin these days with covid ( not bad symptoms and in to day 8 now). So had time and was trying to revise stuff I learnt in Uni 40 years ago. Calculus, limits, field theory and string theory. its really heavy and this is heavy too. Thanks. please try to break it down further if you can as to why those calculation or the process of dither as well thanks. thanks thanks.

@boodlewoodle 3 года назад

Great video but could you do it again and exsplain in more detail the settings and how you put them into PhD as I found it totally confusing and there are literally no videos out there that do this that would be awesome 🙂

@AVAstronomy 3 года назад

There’s really not a whole lot you have to do in phd2 regarding dithering other than setting the method: spiral, random, etc and the dither amount. 1,2,3,4... If there’s something in particular you are struggling with email me and I’ll see what I can do to help. 👍 avastronomy@gmail.com

@tomng1719 3 года назад

Great tip on dithering scale! However I think the comparison wasn't a fair one. The "noise" you saw with the undithered stacked image is caused by heat and is static -- so actually, the longer the total exposure time, the more visible the noise pattern will be on the final result. A fairer comparison would be 3 frames of undithered vs. dithered. That said, dithering is always worth it. Dither or die!

@toriqo 2 года назад

you're wrong. you can clearly see it's walking noise, caused by the lack of dithering

@michaelbibby8636 Год назад

@@toriqo From my very limited experience (I'm new to astro), with livestacking in Sharpcap, 'walking noise' gets worse and worse with more integration-- it compounds over time, so that rather than more subs reducing the effect it actually makes it worse. This was one of my first lessons: more frames does not always reduce noise, sometimes it actually increases it. It would be interesting to compare the same number of dithered and undithered frames as Tom suggests. But its likely a moot point, because given the choice between dithering and not the decision always clearly falls on the side of dithering. Thanks for the useful information in your video re dithering calculator, it should take out some of the guess work for me.

@toriqo Год назад

@@michaelbibby8636 there's a difference between bias/offset noise (which you experienced while live stacking) and thermal noise, which grows with the exposure length. there's also the read noise, which comes from LACK of signal. so, you get rid of bias/offset (walking noise) noise by dithering, you get rid of thermal noise by cooling the camera/taking dark frames and you get rid of read noise by exposing enought to increase your snr thus, swamping the read noise. bottom line, the more frames you have, the higher the snr, the lower the noise. bias and thermal are taken care of by the proper use of equipment (diither, bias frames and dark frames). hope i'm making sense and this will help

@michaelbibby8636 Год назад

@@toriqo The only point I was trying to make, which speaks to Tom's comment, is that walking noise gets worse with stacking. And the noise in your undithered image looks like walking noise (which gets worse over time). So it actually makes sense to compare the same number of dithered and undithered frames.

@toriqo Год назад

@@michaelbibby8636 and the point i was trying to make (initially) was to Tom's comment as well in regard to his remark about the noise being caused by heat, which is wrong. walking noise is caused by the camera's offset, it is static and it has nothing to do with thermal. that noise is present at any exposure lenght, any temperature, everytime.

@michaelgalaxy 2 года назад

I don't think we want to universally recommend 30 pixels for everybody. The formula is correct, but the number 30 doesn't apply to everybody's camera. What you want to do is take one of your pictures (un-dithered) and then gradually bin that photo (in software) and visually observe when the number of binned pixels causes the noise to be reduced to an acceptable level. This will be completely different for different camera sensors. So, for example, on my camera, by binning up 8x8 that does a really good job of averaging out the surrounding pixels, so I might try a target dithering amount of 8 or 16 pixels instead of 30 pixels. Then use the image scale formulas that your described in the video to match that to the guide camera.

@AVAstronomy 2 года назад

Awesome tip! I will definitely look into that for my camera set up. Thank you

@michaelgalaxy 2 года назад

@@AVAstronomy Thanks for the great video = )

@dankahraman354 3 года назад

Is the dither level for APT controlling the mount and thus automatic? What if you are acquiring with images outside of APT? My camera's software doesn't give colour images if they are acquired in APT. I will post the same question on the APT Forum.

@AVAstronomy 3 года назад

Great question, I don’t have any useful advice to offer on this particular situation as I’ve not experienced it before. Hopefully APT forums will offer some good advice

@dankahraman354 3 года назад

@@AVAstronomy I can't follow Kaminsky's explanation too well. In my case the ratios between guide camera and imaging/scope image scales are slightly over 3.

@dankahraman354 3 года назад

@@AVAstronomy Aaron, if I am doing 2 minute subs and my settling time is 15 seconds and I am dithering with each sub do I add the interval of 15 seconds between each frame?

@AVAstronomy 3 года назад

@@dankahraman354 not sure what your asking but overall yes, dithering every frame is going to lower the number of frames your gonna get per hour. I’m sure you knew that but really not much else for you to do. Just set it and let it do it’s thing. 👍

@dankahraman354 3 года назад

@@AVAstronomy I did the calculations for image scale for the two systems (guiding and imaging). If I aim for 10 pixel movement of dither in imager, it should be 3.1 pixels in the guide camera. Now I have to determine the settling times in seconds, dither level and dither scale. It is the last 3 items I haven't figured out yet.

@Safestassets 2 года назад

Can you please help verify that I am doing this right and my numbers are accurate? 1. I calculated pixel scale of my guide scope (Sky Watcher 72ED) combined with my guide camera (ZWO 224) using astronomy tools website. (came to 1.84) 2. I then calculated pixel scale of my main scope (Explore Scientific 102ED) combined with my main camera (ZWO 294MC PRO). (Came to 1.67) 3. I then divided the guide camera by the imaging camera to get dither scale. 1.84/1.67 = 1.10 4. I then divided 30 by 1.1 to get 27.27 (30 being the aggressive dither). 5. Finally, to get close to that 27 number, I set the dither level to 5 in APT and PHD set scale to 5. (5 x 5 =25).

@AVAstronomy 2 года назад

Yes sir. That is correct. 👍

@Safestassets 2 года назад

@@AVAstronomy Awesome! Thanks man. Dithering is taking up to 2 mins in between images for some reason and I thought it might have to do with my calculations.

@erni898 3 года назад

Hi, thanks for your Video. I made my calculation too. and give some result: dither scale is 2.9/2.571= 1.16 to move 30 pixels need to divide 30/1.16 = 25 so i have 25, and here i question: which dither level you recommend use in APT? and in PHD2 dither setting Scale? here i little bit stuck. In your video your PHD2 dither scale is 1 not 4 Thank you.

@AVAstronomy 3 года назад

It all depends on your dither scale. You’ll need to adjust the numbers in phd2 and APT to get close to that 25. Also, “ball parking”. It is good enough. Also, be sure to keep it on random and not spiral. Clear skies!

@erni898 3 года назад

@@AVAstronomy yes of course, but what i mean. Ok we calculate and now i have this digits 25. ok. But where i can find Scale for adapt this digits to PHD2 scale and APT? 25 which digit i need use in PHD2 for example, sorry but i dot understand exactly this moment. Thanks for your answer.

@AVAstronomy 3 года назад

@@erni898 it’s no problem at all Ernest. Glad to help. So what you do is take the scale from APT and PHD2 and choose the correct numbers from each program to multiply together and get as close to 25 as possible. So for you that would be setting APT to 5 and PHD2 to 5. That will attain your goal of 25. Does that help?

@erni898 3 года назад

@@AVAstronomy a ha ha O man. Thanks, now its Clear! heh :) Ok I waiting clear styes for try it, we have terrible conditions now, but i hope this weekend i have one night finally. Thank you very much

@johnnyredfireastroimaging5266 3 года назад

How would I set that for asiair? To move 30 pixel I need 12.97

@AVAstronomy 3 года назад

Johnnyredfire AstroImaging great question. I unfortunately am still “old school” and use a laptop. Astroruz or astroaddict might have some info. On this. Good luck! Clear skies and God Bless!

@johnnyredfireastroimaging5266 3 года назад

Well it has a selections of 1 pixel, 2, 3, 4, 5. I assume this is multiple by the guide scale which mine is 4.985. If 30 I think that’s super aggressive at 5pix.....just a guess

@AVAstronomy 3 года назад

Johnnyredfire AstroImaging experiment. I’d say try 3 or 4 and see how it goes. 👍

@AstroSeabee Год назад

I have the ASI120MC-S. My quite scope is a SV Bony 30mm I think. I still can’t figure out my right numbers.

@AstroSeabee Год назад

Quite scope not quite scope. I’m On the phone sorry.

@AstroSeabee Год назад

Guide

@AVAstronomy Год назад

Send me the focal length of both scopes and the sensor specs of your camera and I’ll see what I can come up for you.

@AstroSeabee Год назад

@@AVAstronomy William Optics Zenithstar 61 at 360mm. I normally use canons. They are T3i, t5 and t7. I believe the pixel size is the same for all. 4.22. That’s what I always use in Pixinsight at least for photometric color calibration. I have TBI from a mortar blast in Iraq and this type of stuff confuses me. 😂

@AstroSeabee Год назад

I know the guidescope is 30mm. The ZWO I’m not sure about looking for the box

@joshuacarter3478 3 года назад

Hey man, love the channel. I calculated my dither and came up with 2.87. I am using nikon d750 on 600mm scope. Guider is Orion SSAG on 50mm guide scope. Does this even sound correct? This would make my settings be 3 in dither level and scale of 1 in PHD2. Seems low or is this about right. Thanks for the videos.

@AVAstronomy 3 года назад

Something sounds off. Can tell me the pixel size of your cameras and focal length on both scopes?

@joshuacarter3478 3 года назад

@@AVAstronomy yes I was off with my math. Guider is Orion SSAG (5.2 micron 50mm guide scope). DSLR is Nikon D750 (5.97 micron at 600mm scope). I think math comes out to 10.4. So this would mean for every 1 move on guider my dslr moves 10.4 pixels yes? So if i want a 30 pixel dither I should set Acquisition software at level 3 and PHD2 to 1 and that would be 30 ish. I think that's it. I had to get slide rule and graphing calculator out. Lol!

@AVAstronomy 3 года назад

@@joshuacarter3478 what’s the focal length of the guidescope? I believe the 50mm is your aperture. Need the focal length. Should be around 200mm I think..

@joshuacarter3478 3 года назад

@@AVAstronomy dang it! Yes you are correct. It is 162 mm

@joshuacarter3478 3 года назад

And I looked at that a million times, not sure why I kept saying 50mm

@nathanhassey4724 3 года назад

Shout out to the Burrito Coloring pages google history! The things my kids ask to color is hilarious as well. Video was great Btw!

@AVAstronomy 3 года назад

What's this thing with people stopping my video so they can see what's in my search bar? It's kinda creepy. Guess I need to start blurring that out in future videos. Anywho, thanks for watching.

@nathanhassey4724 3 года назад

@@AVAstronomy actually I didn’t pause anything. Just read it as it popped up.

@AVAstronomy 3 года назад

@@nathanhassey4724 no worries, it just weirds me out a bit. Your comment was harmless and quite funny actually, you’re right. It is funny the things our kids ask us to print. Clear skies!

@nathanhassey4724 3 года назад

@@AVAstronomy Sorry for weirding you out, wasn't my intention. To change subject, how often do you dither? Every frame? Also, in PHD2 is it the scale number that needs to be adjusted? I didn't see you change anything in the PHD2 settings. Thanks!

@AVAstronomy 3 года назад

@@nathanhassey4724 It’s all good, I dither every frame. Some people say every other frame is OK but I have found every frame to be noticeably better. Also, I have a separate video that teaches how to do the proper dither scale. It’s called how to dither and do it right.

@mahadahmedbaloch Год назад

How to dither. Is it an option in photoshop?

@AVAstronomy Год назад

It is not. Perhaps one day there will be a plug-in that simulates dithering but we’re not there yet.

@mahadahmedbaloch Год назад

@@AVAstronomy then what is dithering

@AVAstronomy Год назад

@@mahadahmedbaloch dithering is moving the mounts position by really small movements. This causes the pattern noise to become random noise and therefore cancels out the noise. It is a powerful technique to reduce noise.

@dedskin1 3 года назад

Wait 72 frames vs 3 . That makes no sense , 25h of undithered data , should in theory beat 1h of dithered data . The way im looking at it dither helps about 2-3x SNR , but you also need 2-3x the time to collect the data . So you dont get something for nothing . But i didnt do dithering still , didnt have a guider , now i do have it and i can dither , ill do it soon , i would like if it was like this , it would be perfect but i doubt it .

@AVAstronomy 3 года назад

Dithering greatly reduces color mottle in your images. I’ve found dithering every other frame to be a good happy medium. Clear skies!

@dedskin1 3 года назад

@@AVAstronomy Yes i know , but what im doubting is that it is 20x better , i still think 1h of dither would be worse then 20h without dither. In SNR terms

@AVAstronomy 3 года назад

@@dedskin1 sounds like a great test idea. Let me know how it comes out. But for all practical reasons, I’ve I’m going to put 8-10 hours in a target, I know from personal imaging experience I will get better results dithering every other frame than not dithering at all. I’ve noticed a tremendous difference

@dedskin1 3 года назад

@@AVAstronomy If you have time to do that would be nice , i struggle with time , there are always clouds ,and when there is no clouds i can barely get 1-2h . Now im picking up , but still i have to go to work , so i have to pack things up around 1AM , so i get around 1-2h of actual data . I envy you if you can get 4-8h , thats pure gold right there :) Money shot :)