Why Dithering is Important | Setting it Up With the ASIAIR
ฝัง
- เผยแพร่เมื่อ 25 มิ.ย. 2024
- In this video, we go over dithering with the ASI AIR, and why dithering is important. Noise is a problem with astrophotography images, and dithering helps reduce it before you begin processing. This works for all versions as well, so you don't need the Plus!
This video is NOT sponsored.
While all Astronomy stores are great, I HIGHLY recommend Agena Astro. Check them out here: agenaastro.com/?rfsn=7382645....
⌨ 📢 Join my Discord! / discord 📲 📲
Check out my images at astroescape.com
Follow me on Instagram: / astro_escape
QOTD: Have you manually dithered before? If so, how did it go?
Please do subscribe if you haven't: / @astroescape
My Astro Gear:
Skywatcher HEQ5 Pro: amzn.to/3yJSfVU (Amazon)
Skywatcher HEQ5 Pro: bit.ly/3oam0NL (Agena Astro)
William Optics Zenithstar 61: bit.ly/3IiEv9E (Agena Astro)
ZWO ASI294MC Pro: bit.ly/3o3Fd3R (Agena Astro)
ZWO ASI Air Plus Kit: bit.ly/3Ilevua (Agena Astro)
AC to DC 12V Power Adapter: amzn.to/3CNEx4h
EQMOD Cable (to connect ASI AIR to HEQ-5): amzn.to/3u7eUrO
Recording Gear for the Curious:
Camera: amzn.to/3BQjJKn
Microphone: amzn.to/3E17I7R
Tripod: amzn.to/3Ci0haW
DISCLAIMER: This video and description contain affiliate links, which means that if you click on one of the product links, I’ll receive a small commission. This helps support the channel and allows me to continue to make videos like this, and pay for replacement screws I've dropped in the dark. Thank you for the support!
Thank you Daylon, your AA+ videos are fantastic! Please keep ‘em coming.
Will do! Thank you for the feedback!
thanks man, your ASIAIR tutorials are really helping me over here!
That's awesome Keeslp! I'm glad the videos are helping!
Just answered a few of my questions . Great job
Sweet! If you have more questions, feel free to ask!
Nice explanation of dithering - the "blink-movie" presentation of the effect is extremely clear. I also settled on a similar strategy for dithering, minimizing downtime waiting for guiding to settle. While I'm using different software (SharpCap/PHD2 rather than the ASIAir), the concept is identical, and most software seems to have very similar dithering controls available. After some experimentation, I also tended towards one dither every 3-4 frames when taking shorter subs (45-90 seconds typically for my site), but go back to dithering every frame when taking long subs (10 minutes or more, useful with narrow-band or under dark skies). Cheers!
Your point about longer frames vs shorter frames is a good one. Thank you for that! Yeah I've seen how other software compares, and the process is remarkably similar. But, when it's doing the same function, it's kind of hard to make it different. Thanks for watching, Bob!
Excellent video
My favorite part kids cheers in background 😄
It was fun to edit in too!
You are my ASIAIR PLUS guru! 😃
Thank you for the kind words, Jim!
Wim Nelissen from The Netherlands. Thanks for your explanation on dithering, very clear. One thing : when setting some numbers you say in stability 2 degree, but I guess you ment 2"( = arcsec). It is just a 3600 times difference. Reg. Wim
Yeah, I did. Thanks for the catch!
Great video. IS there also a way to do dithering with Asiair, without using autoguiding? If you do not want to use a guidescope and cam?
You still need to use a guide camera. The main camera is focused on capturing your target. As of now, doing both with one camera doesn't work.
One nice way to save a little bit of time and your imaging is to set it up to dinner every two or three images. You still get the same affect but you don’t have to wait for the guiding to settle as often.
True. Shorter exposures only need every few frames, but longer frames such as 5 minutes, some people tend to dither every frame.
when its this cold, i manually dither every night, the asiair allows me to stay in doors with no dither :)
I would still dither in case a pixel on your camera's sensor has a malfunction. Calibration frames can detect those and average them out.
I've done manual dithering. I used my mounts controller on the slowest speed and every 5 shots, I'd stop and make a quick adjustment, then keep going. It worked well, but I've moved to an ASI AIR so I don't do that anymore.
Nice. The ASI AIR makes it so much simpler :)
Daylon, any ideas as to why my dithering stops after 4 or 5 exposures using a dslr and asi air plus? Turned it on and dithered every other frame then would not dither anymore. Tracking was very good also.
That's odd. How was the weather when it did that? Your guide scope may have lost the stars with a very thin layer of clouds up there.
I use an AVX mount which is connected to the ASIAir via a USB cable connected to the handset. I wonder how well dithering will work on this mount. Thanks
It should still work. All it does is send small movement signals to the mount.
For manual dithering, instead of losening a ball head, couldn't you just kick a random tripod leg between exposures?
I have the asiair plus also, and I use the asi294mc pro, and 2600mc pro. Since the asiair does not let you select a dark flat option, can I just select bias, and use that to take the dark flats? I am assuming with my cameras, it's better to use dark flats than bias frames anyways.
Take darks with the same exposure time as your flats. If you do that directly after taking flats, the ASIAIR recognizes it and will use whatever the auto timer for flats set. Just make sure to select those as dark flats when stacking.
I’d love for you to explain this in one of your videos.
Yes, just use BIAS in Autorun at same exposure as Flats. Works great with 2600mm Pro
I have found a 2 second push of the east or west and south or north on a go to mount will provide good dithering. Use a random pattern for this method when pushing a direction button on hand controller.
That's a nice method if you have a hand controller. When I thought up the example I put into the video, I thought of star trackers! Thanks for the suggestion for those that are using a hand controller 😃
Daylon, what were you using to connect your ASIAir Plus to the mount before you changed to the EQmod cable? That is what I'm using now and I'm going to try the USB connection instead just for fun (if and when the weather clears). The Plus will connect to the mount over USB without any modification which my Pro would not. Also..... I am dithering 3 pixels every frame, I notice that you doing it every 2 pixels every 3 frames. My images usually turn out sharp as a tack, but it takes FOREVER to shoot a lot of frames because of the time it takes the auto guider to settle back down. Have you done it every frame and changed the way you dither? I may try every three and see what it does. Thanks a bunch for the video, I have picked up a lot from you and everyone else that runs You Tube channels!
I've always kept it at every three frames, which I explain towards the end of the video. It's because of the settle time. I know at minimum you'll have to add SOME time to wait for things like dithering or a meridian flip, but the goal is to minimize that wait time by skipping a few frames for dithering. Which, can allow time for a few extra frames. I have messed with every frame a few times, the extra wait time wasn't worth it to me. Granted, I did that when the Eastern US sky was just clearing from the wildfire smoke this past summer..... the smoke wasn't helping the guiding.
I use this method before the EQMod cable: Mount -> Hand controller -> USB Cable -> ASI AIR Pro. The hand controller and the ASIAIR weren't playing nice, it kept changing which hemisphere I was on when slewing. So, I bought the cable when I got home from that trip! The mount I have doesn't have USB connections. If the mount has a USB connection, you don't need the EQMod cable.
Thanks for your compliments!
@@AstroEscape As soon as the sky clears I'll give the every 3 frames a roll and see how that works. As far as the cable goes, my hand controller is something I paid for with the mount and have next to never used. The mount and the EQmod cable get along great. Wildfire smoke.... I live in Southern Idaho. It's never a matter of if we'll get it, it is a matter of much, how long will it last, what direction is it coming from and yeah this one I can see flames and the air tankers. Having said that I wouldn't live anywhere else.
@@AstroEscape "If the mount has a USB connection, you don't need the EQMod cable." Except for newer revisions of the EQ6-R, where it seems SkyWatcher has updated the chipset they are using from PL2303 to PL23D3 (USB to UART RS232 Serial chip), which is a model not yet supported by the stable Linux Kernel (ie: ASIAir). USB wont connect (even at 115200), but EQMod cable works fine here. Solid video, thanks for the upload.
@@hurdpcs2802 Oh my! Living that close to the source of the wildfire smoke would be a huge struggle for clear nights! I feel you with using the hand controller. Maybe if I decided to get a scope for visual for outreach events I'd use it, other than that it sits on a shelf.
@@MazzifLOL Thanks for the correction, I didn't know Skywatcher did that. That's a bummer, hopefully ZWO recognizes that and helps get things going for compatibility!
If it could take 60 second to settle, that time added to each frame could add maybe 30 minutes to a 30 frame capture.
Would it be better to use that time to capture more frames?
Maybe it depends on if the camera has low noise vs a camera with higher noise level.
Yes, it would. But if it's taking 60 seconds to settle, then usually something is going on with your guiding. Either the guiding is off, or the sky conditions are bad.
You say you dither 2 pixels every three frames with your guide camera/telescope. Is this related to the focal length of the telescope and sensor pixel size? What should the dither setting be for different guide scopes and sensors? In my astrophotos I see much noise so wonder if this is because of incorrect dithering.
A bit of that but also exposure length. If you were say, doing five minute exposures, you would want to dither every frame. Shorter lengths you can dither in between a set number of frames and still get the intended result. Two pixels per 3 frames tends to work for me. The other thing to take into account is how much time your guide camera needs to settle before the main camera starts shooting again. If your guiding is accurate, it won't take long but if a surprise thin cloud shows up it could slow things down a bit.
Will this thing Asiair plus work with a explorer iEXOS-100 PMC mount?
From what I've seen, it takes a bit of tinkering but it does work. I don't have that mount so I've never had a chance to mess with it. This board should be able to point you in the right direction though: espmc-eight.groups.io/g/PMC-EightApplication/search?q=%23ASIAir&ct=1
@@AstroEscape thanks:
Does that mean if my guiding is not good I should not use dithering.
No, I'd still use it. I'd try to fix the problem with the guiding too. Either way, dithering still helps... you know the saying, right?
Can you dither if you're not guiding?
Technically, yes. Manually. In between pics make a very, very small adjustment to the framing by moving the camera on the mount a tiny bit. But it's time consuming and runs the risk of messing up framing on the object entirely.
Dithering only works properly with an undersampled image
I agree, but it still helps with noise reduction!