Lucky Imaging

[xelasnave]

Even before I came across the concept of lucky imaging I felt lots of short subs is better than fewer long subs...

So check this video to hear how it is done...I have been doing 30 second subs but apparently under one second is the go:eyepop:

But I loved hearing the presentor say "high iso and short subs" or close to that:D

It is a little drawn out but worth watching all the way thru and I am sure everyone will be able to relate to "things going wrong" ....

https://youtu.be/5s9xbZ5G-wk

[RyanJones]

It’s an interesting topic. Myself and Stephàne have been discussing this topic recently. One of the challenges that presents itself though is how many images you have to stack in your integration. I for one don’t have a computer that can handle several thousand 30mb files. Also atmospheric disturbances are helping to hide flaws in my optics lol. The shaper the image, the more I’m going to see lol.

Ryan

[Startrek]

Alex

I’m regard to lucky imaging , I’ve watched Cuiv the lazy geek for a while and he uses lucky imaging techniques too from his apartment balcony in the centre of Tokyo Bortle 9

Some of his Galaxy images are absolutely incredible however they required hundreds and hundreds ( up to 1000 ) of 20 to 30 sec subs

For those who use the new generation cameras QHY268 or ZWO2600 series , these produce 50MB files and therefore you require a computer with huge storage and processing power if your going to pursue this technique long term

Cuiv has many computers and remote storage so he is well set up for this type of imaging

He’s proven that good images can be achieved under adverse conditions using this technique

He’s also posted some of his images on CN

Check his YouTube channel out , there’s a episode on it a year or 2 ago about lucky imaging

Martin

[xelasnave]

Hi Martin..I follow Cuiv (subscribed) and really like his content..in fact he convinced me to tryout the Asiair plus and started me down the road to learning the important stuff in imaging.

My little lap top manages rather well (better than my fesk top actually) but my daughter has given me her old gaming computer and she is going to rebuild it for me to make it pretty flash and dedicated to stacking primarily...everything will be replaced except the case and power supply;)..I could buy one built but she has just built a rather decent one and I would like to give her more experience in building...I will have the components list very soon so I plan to open a thread in the computer section seeking input as to if we/she has made the best selection of bits...

Currently what I do is to run an external drive off the lap top so huge files is not a problem...I use 3x drizzle which without the external drive gives me messages like...you need 350gig space and you only have 120 gig available...but with the external drive there is no problem..as I type I am stacking 231 subs from the ZWO 2600 OSC and did 350 from the Mono earlier...I am going to try and stack both later today to push the limits:D I have not idea how that will go:D

After watching that video I am going to see just how high I can push the gain and how short the subs on the 115 mm and later on the RASA which is down having new heater ring fitted and attention to cabling.

Alex

[Dave882]

It’s indeed a very interesting prospect. I’m still skeptical about how “deep” you can go with very short exposures even if stacking 1000s together. This however is only based on my eaa experience and the big difference in depth obtained by for example 10min of 60sec exposures vs 10min of 10sec exposures.

I know there are some calculations to determine the minimum exposures required to overdone sky noise or something like that. I’m guessing that might have something to do with it.

Having said this, for brighter targets it’ll be excellent. I was doing a little project on the homunucleus nebula (nice and bright) and took a variety of exposures with my c14 @3900mm of different lengths from 2min down to 0.5sec. The difference in detail I got in the lobes was huge. I ended up learning I needed exposures under 500ms, and will revisit when Carinas back up. Anything over 2sec was a write-off in comparison. But this is now verging on planetary imaging so none of this should be any surprise.

It’s so hard to do an apples for apples comparison with stuff like this, because even with planetary lucky imaging the seeing and sky transparency changes so much from night to night.

[Stephane]

Hi Alex, what an interesting topic. One point I learnt in the video is that to double resolution (according to some Exeter University paper), exposures need to be less than a second and only the best 10% are used. That’s a lot of effort for marginal gain. However the idea that we amateur astrophotographers can theoretically even slightly break past the limiting factor caused by our atmosphere is very exciting indeed.

Astrobiscuit has a discord server where several imagers combine their data for DSO lucky imaging. I look forward to seeing what they can achieve. Perhaps we will start to see more of this type of astrophotography in the future. I would like to give this a go one day, but still have much to learn in the mean time.

[xelasnave]

Look at the whole video and at least the end where he displays an image that he and another member of Bat contributed.
Alex

[Dave882]

At 22:40 he says they got some lucky imaging data from 2 people, but also included 385hrs of other longer exposure data gathered by other contributors. The final image includes all the data as far as I can tell. I would love to see the result from JUST the lucky imaging data but I suspect it would not be nearly as deep as the final product. You simply can not pick up that really faint data with sub-second exposures with a normal size telescope. Detail within a bright galaxy core or PN… well that may be a different story.

[xelasnave]

I always go for at least 385 hours:lol::lol::lol:

How do you get 385 hours?

How do they check subs is what I would like to know..it near sends me bats with only with a couple of hundred...
I am trying to stack 510 at the moment ..a couple of hours to go and it has been going for six hours ..trying to stack OSC and Mono but I am not hopeful as I have had two failures already...but I do have a stack of OSC and a stack of HA to combine in Startools when this current stack is complete...so I will see if they can be combined later tonight...it would be great if the total stack works and use it as a luminance...but so far the two stacks look pretty decent leaving aside the aspect of colour...

I have not looked at the sky but the lappy is tied up stacking ...

Alex

[gb44]

Hi Alex

I would use ImagePlus' grade tool for sorting out the best frames to stack. Maybe accept the best 10%

On short exposure/high gain topic I have followed Łukasz Sujka on Astrobin and he has posted pics of PN taken with these techniques. Really good stuff.
Heres a link to a pic of his https://www.astrobin.com/418782/
I do remember he said he would check even 800 frames individually to get a decent stack.

Here's what he reckons/writes
<<Welll, It's quite difficult to find some tutorial.
But in general there is few important rules which I think are the most important:

- camera with low readout noise (1eV-2eV or less) - ASI 178, 183, 290 - cooled versions
- bigger aperture 8'' minimum. 10'' is ok, 12'' or more really nice :)
- a lot of subs - 300 is absolute minimum. Good standard is 1000. But of course more is better
- high gain to achieve lowest redout noise as possible (80-85% is what I usually use)
- short subs - usually below 10s. But less is better :)
- stacking in Siril or Autostakkert3
- processing like normal photos with more agressive stretch>>

GlennB:)

[glend]

Hmm, 385 hours of my life? And that's just combined imaging time. I too use terabyte drives to over come laptop storage restrictions, but cannot see building the equivalent of a Bitcoin processing machine to do Hyper EAA.
Too expensive, time wise for me. Good luck.

[xelasnave]

Thanks for drawing all that to my attention ..much appreciated.

Alex

[xelasnave]

Well I have the benefit of time on my hands and many many decades ahead to get all this done.;)

Alex

[xelasnave]

Well the good news..the huge stack of both OSC and Mono went thru but for whatever reason the file sizes are different for individual stacks so I cant combine in Startools..I will just process the stacked OSC and Mono image and see how that turns out as getting that done was the main goal really.
I hope to open a new thread later and post the result.
Alex

[glend]

Can you not just layer them in Photoshop?

[Rerouter]

The process was decided to be stacks of stacks early on, For the first test object of eagle nebula about 1 year back I got about 17,000 non lucky subs from people to answer if we needed every sub, or only well done stacks

Once you have that stack it gets combined with others with some very detailed pixinsight tricks to keep it in linear space as much as possible, the write up for the image on astrobin goes into the process used for that image.

How it started was I took a question too seriously and kick started the BAT almost 1 year ago, working out what the limits where and what programs could be used, but now its evolved into its own thing with smarter people than me :) the paper for resolution improvement vs time has some extra factors relating to apeture, but for the 6-14 inch for amateur's its close enough to not worry about,

He did actually show the stacked lucky image in the video when he was talking at the end on discord, that and some other lucky contributions were given a higher weight than the deeper data from what I can understand to preserve there details,

[xelasnave]

with different sizes it is not easy even in Photo Shop...at least for me.
alex

[Dave882]

It may or may not be the best option available, but APP (astro pixel processor) handles data from different sources, sizes, cameras, scopes etc quite easily. It’ll stack it all together without any problems. The only challenge is blending the seams if there is an overlap between data with vastly different LP or noise profile. Then you can play with the fits file in startools or ps etc.

[xelasnave]

You are the most famous person that I have ever spoken to:D...good on you and thanks for contributing here.

When I get the RASA 11 working to my satisfaction I hope to perhaps go for 5 to 10 second subs as so far all my experiments point to that working for me..which may not fit the science but out of the available approaches I think that may work for me...certainly with the funny seeing of late...I am lucky in so far as I dont know what I should be doing so I am not limited to low gain for example:P

thanks again

alex

[Dave882]

Thanks for that explanation. Yes blending the lucky stack in with the deeper data will certainly add something positive (with the right post processing skills!!). I’d be very interested to know how Light Pollution is factored into the resolution equation. After seeing some results from others I’d be keen to try and hit some PNs (or even galaxies) lucky imaging with my c14 but feel I may be restricted by B6/7 LP at my location limiting me to only the brightest targets.

[gb44]

<<I’d be very interested to know how Light Pollution is factored into the resolution equation. After seeing some results from others I’d be keen to try and hit some PNs (or even galaxies) lucky imaging with my c14 but feel I may be restricted by B6/7 LP at my location limiting me to only the brightest targets.>>

Dave,
I tried to get the PN in M22 - from light polluted GoldCoast.
Used IDAS LPS filter 85x30s High Gain 2, offset12, 0degrees.
Crop is ok but no PN seen - Ive yet to go to the higher gain/shorter exposure Alex is using. Less bloat at least...


GlennB

[glend]

Alex is lucky enough to live in a very dark location, far away from light sources. This provides an environment to experiment, off of a dark baseline, which is not available to many others. Photon arrival rates, during very short subs, would simply be lost in the light dome of major population centres, no matter how you try to filter it.

[Startrek]

Here’s a couple of Galaxy images from Tokyo City Bortle 9 white zone from Cuiv using lucky imaging with his 8” Newt and EQ6 mount
Exposures were 10 sec and 30 sec , hundreds and hundreds of subs
Absolutely incredible what can be achieved in the worst kind of conditions for AP

Resolution is poor due to being copied from a website ( grossly downsized )but you can see the level he can achieve with just basic equipment
Astounding !!

[Rerouter]

https://www.astrobin.com/7ez0pl/

Scroll down to image processing, Stefan did a great job of writing it all up, Mainly each sub needed to be run through multiscale gradient correction to remove any gradients caused by light pollution, It chews some CPU, but it preserves fainter details better,

[Bassnut]

I hadn't heard of this before, deep sky lucky imaging, very interesting indeed. On reading up, the recommended gain setting for a CMOS cam is 350-400 (low read noise). the well depth at 400 is then essentially 8 bit, 256 levels, I understand very short deep sky exposures will not need much dynamic range, but 8 bit ?(pre stretch), that's scary !.
Also, why, instead of manually selecting best subs out of 1000s isn't something like registax planetary software used that automatically grades and selects the sharpest bits of every sub instead of whole subs only.
If there is a reason this kind of application is not appropriate, Ive been testing an automatic way to have the sharpest subs graded (on DS subs, only sharpness nothing else, may not be sufficient) looking promising!.

[Stonius]

I agree Fred, I would have thought StarAlignment in PI would have rescued a bunch of data that they threw away.


Markus

[xelasnave]

I am trying 15 seconds at gain 350 and 450 using the 115 mm and so far it seems ok..I hope to try shorter thru the RASA tonight but the irony is the seeing has greatly improved such that long exposures should work again.

Still dew but you are not swiming in it.

So I have three guide scopes and cameras that again seem useful..I will fit them all today if I get time but the RASA fittings need some more angle grinder work and although that is fast smoothing after takes ages...

Alex

[xelasnave]

Re OSC...at high gain 15 seconds does not work at all..subs are terrible..at 30 seconds high gain results are acceptable.

[oska]

Unfortunately the fog set in later last night so just for fun I had a peek at Orion and it was bright enough to get an image at 1s even with the fog. I was surprised could resolve the bright center stars. I decided to give this a go for fun. Took ~1300 x 1s, ASI1600MC-c gain: 139 offset 25, -10C, no filter. Tried gain 75 and 200 and 1,2,3,5s but settled on 139 & 1.
Stacked 80% in DSS, no calibration. Nina was only grabbing 1 frame every 6-8s so I turned off most of the post processing fluff (except HFR/stars) and got it down to 1 every 2s. Given how the stack blew out the core if I have another go I'll try much lower exposures ~0.1s
I know as an image of Orion it is "decidedly average" but that's not the point ;)

Watching the live stack was soo cool. Noisier! noisy - better...

[xelasnave]

Thanks for contributing John..may I suggest a little "cheat" ..give your core a light touch up with the "burn" tool from either photoshop or Gimp ( free and for most purposes as good as photoshop) ...the burn tool selectively darkens an area and I suspect a gentle application may bring out four little stars...maybe...but it is a handy tool for situations where you need to brighten or darken just part of an image...

I must try your approach thanks again.
Alex

[oska]

Cheers for the tip, never even heard of it. I was trying at higher gains to play with that concept but anything above unity sucked. Need to go shorter, by a lot I'm guessing, on such a bright target. I don't care if it amounts to anything: it's fun just trying it out :)

[Stonius]

So how did it compare, John? Were the stars smaller? Was there less noise? Just curious what gains were had. My understanding with the video posted earlier in this thread was that it was supposed to bring out fine details.


Markus

[oska]

Sorry, the lower gain were much noisier and the 2,3,5s and 200 gain were all blowing out the core.

Here's an ezSoftStretch of the best/worst sub as scored by DSS and the test shots I could find for 3 & 5 secs.

[Stonius]

Thanks John! :-)