Stacking - I just dont get it.

[toryglen-boy]

Hi there

Matbe some of the kind patrons here, will end my suffering, and tell me what i am doing wrong, i have tried stacking in the past, but the results always look terrible, am i doing something wrong?

Image 1, is an 8 min shot of the Lagon Nebula

Image 2, is three of these shots stacked.

I know lots of smaller exposures and probably better than a few larger ones, but i am just trying to learn the broad strokes of my craft, before losing any more heart.

Apologies for the way i am typing, i have been watching Deadwood again

;)

Anyway, 3 stacked images and it looks awful. Where are the best tutorials? how is anyone meant to get a nice picture out of this?

PS. The over saturation of blue is the LPR, i am starting to think only totally dark skies will suffice. But even without the LPR, i still get a background of very light grey

Can anyone offer any help for the best settings when stacking, and any hints or tips for getting the best out of something that to me, looks unworkable?

thanks..

[Matty P]

Hi Duncan,

What software are you using for stacking? I am assuming that you are using DSS.

It is very odd for your stacked images to appear like they do. Usually when final stacked images are very dark and need futher processing to bring out the object.

I am not sure what you are doing wrong? Could you maybe explain the process you are using? This may help us uncover what is going wrong. ;)

:thumbsup:

[Jazza]

Hi Duncan, I don't think there is actually anything wrong with your result - merely that the levels are set badly.
Post processing is usually required to set these (in PS or similiar) I'm sure someone will reply in more detail, but do a bit of a search in how to set levels (and what the histograms mean) and it might help.
Jay

[troypiggo]

You can stack all those images any which way, but it still won't produce an image of the Lagoon Nebula ;)

Sorry, couldn't resist :)

[TheDecepticon]

Hi Duncan, I'm not sure why DSS does this, it does to me as well. I use Photoshop afterwards to set the white point accurately, set the black point to not clip the data and then use the gray scale to set the mid tone/ reduce the greying. Try playing with your levels while watching your histogram in Photoshop. If you setup DSS with the recommended settings, it should align the channels and get rid of the blue sky also. Maybe purchase Jerry Lodrigus's book "Photoshop for Astronomy", it is a great resource and can be attributed to the step forward in my images.
Good luck!:)

[White Rabbit]

Ok, my processing chops arnt great, I'm still learning as well but I have the same gear and filter as you do and heres what I've found.

First of are you shooting in Raw yet, i recall you were shooting in jpeg before?? If you are, you can tame that blue tone by reseting your white balance in the canon photo professional.
Double click on the image you want to edit then right click/tools then there are three tabs up the top of the tools window select raw. Youll see a button that say "Tune" click on that and you see the "White balance fine adjustment" box come up. Click anywhere on the circle and you will see the picture change in colour. Select a spot that looks best, right click and save the ricipe to the clip board and then hight light all the images that you are going to stack, right click on one of images the and paste the recipe file/apply to all images. This will set the white balance the same for all the images. You can also go into to the rgb tab and aligne all the colours but i think most people do that in photo shop. Do you have photo shop? Your going to have to get something like it because there is only so much that you can do in the canon app.

Now open your stacking soft ware and stack. You'll probably still get a very pale cast over the image, you can fix this in photo shop with "Levels" or if you are using the canon app you'll need to use brightness and contrast in either the raw or rgb page in the tool palate. You can do a decent job with just the canon app, at least to noob eyes anyway.

Anyway thats a place to start from, hope it helps.

Sandy

[White Rabbit]

Here is a quick 2 min job in the canon app. all I did was realign the colour channels and adjusted the brightness and contrast. The monitor on laptop hasnt been calibrated for colour so the colours might look off on yours.

Oh, and thats the trifid neb btw ;)
sandy

[White Rabbit]

Doh!! thats the wrong image 2 secs.

[White Rabbit]

Here it is, btw what iso are you shooting in because there is a lot of noise in the image, you'll need a lot more subs to get it down a bit.

[toryglen-boy]

so many great replys, thanks.

I usually shoot at around ISO 800, and thats what these images are. I know these images are filled with noise, but i was just messing around with exposure times.

The problem i always find, is that apart from noise, images always look like a washed out grey, and what was in colour, ends up looking monochrome. With stacking, i should have thought the images would have gotten brighter, and colours more intense, but it just ends up looking really washed out. TBH, i am starting to lose heart somewhat.

It seems that any exposure over about 3 mins, starts getting shockingly bad noise, so for a 3 mins shot, whats the point in guiding?

I am wondering if IRIS would do a different/better job

any more input welcomed.


and yes, i know its not the Lagoon nebula

:P

[Omaroo]

Don't lose heart Duncan. Everyone starts out the same way - it makes sense all of a sudden when someone else understands what you're attempting, and offers the right help to counter it.

Can we ask that you post the exact stacking mode you're using, and what stacking parameters you're using within that mode in DSS? Then, can you post a link to three or four of your raw subs somewhere?

[toryglen-boy]

Thanks for that Chris, i know people like yourself are on hand to help as best they can. i will post some settings etc. later. i do remember though, the stacking mode is the bottom one "adaptive average" or something like that, and i think i stack darks as median.

lots to learn...

:sadeyes:

[White Rabbit]

Duncan, are you using the in built noise reduction on the camera? It will take dark frames automatically and subtract them from the image. That should take care of most of the noise. You have to hook you camer up to the computer and enable it. Connect the camera to the pc and open the canon utility app then "Camera settings" then I think its menu settings and enable NR and high Iso NR. Set them to auto.

But the steps I wrote above will get rid of that washed out/monochrome look. You just need to realign the colours and do a bit of contrast and brighness adjustment in the canon app, levels and curves if your using photo shop.

I share you pain though, as I'm only slightly ahead of you in the learning curve. As Chris said above, it will fall into place all of a sudden...I'm still waiting lol.

[Octane]

Duncan,

For a start, on the 400D, ISO-800 is going to ruin your images. Seriously, consider fine-tuning your polar alignment and aiming for ISO-400 images (i.e., twice the exposure length).

Forget in-camera noise reduction and take your own dark frames either before you start imaging or after you've finished. This way, you have a lot more control over how you subtract the noise rather than let Canon work its magic (i.e., I don't know how the in-camera noise reduction algorithm works).

Ensure you're shooting in RAW mode only.

As far as my understanding goes, DeepSkyStacker is a more user-friendly IRIS. IRIS' final *.PSD output looks worse than the original cyan-cast image you've posted. You need to take it into Photoshop and manually set the black and white points for each channel using the Levels tool. I'm assuming you will need to do the same thing in your current DSS predicament, too.

If you're interested, I can pop round one of these nights and we can have a look at what's going on.

Regards,
Humayun

[White Rabbit]

Being new to astrophotography, as I am, the less steps I have to perform manually the better. Is there that much difference between using the in built noise reduction to taking your own darks and subtracting them in dss? I'll give it go next time I'm out. I always thought the in built NR did a decent job, but then I have nothing to compare it to as I havent tried it the other way.

Cheers

[toryglen-boy]

Sounds great mate, i will hold you to it

;)

[Omaroo]

Better still.... hands-on. :thumbsup: Onya Humayun. :)

[troypiggo]

I'm having some trouble with my cameras and notebook talking to each other. Mind dropping in here on your way home from Duncan's? :)

[toryglen-boy]

Maybe i can help with that mate, drop me a PM


AWESOME !!

:thumbsup:

[Hagar]

The above statement has me a little confused. I can see no obvious reason to not use ISO800 in fact I can see some very good reasons not to double your exposure length using ISO 400. By doubling the exposure time on a non cooled DSLR the heat generated and noise introduced would far out weigh any gains in using 400ISO. The biggest gains made with a DSLR are in keeping exposure times down while still capturing enough signal and enough frames to allow the stacking algorithims to increase the signal to noise ratio. Longer exposures will only increase the generated noise while the decrease in ISO will reduce the captured signal.

Th use of ICNR is really a personal choise. Proponants of DSLR imaging all have difering thoughts on this and the likes of LEON uses ICNR almost all the time with very good results.

Manually collected dark frames may well do a better job of reducing things like amp glow but I am still to be convinced.

Almost all canon cameras seem to work very happily at 800 ISO while most cooled DSLR's work very well at 1600. Again what ever takes your fancy but the thermal characteristics of Canon CMOS seems to identify thermal noise at exposures over 5 minutes using all ISO settings under dark skies.

Something to think about.

[Octane]

Doug,

Using ISO-800 and above on the newer breed of cameras, such as the 40D and above, and ISO-1600 on the 5D Mark II, may be all well and good. Having done my fair share of imaging using the 300D and the 350D (Duncan's 400D isn't too far removed from the 350D), I know that ISO-800 makes for grainy images (especially, when printed). I'm a fan of printing so I have a bit of a bias there.

I'm not sure if you saw my earlier work, but the large majority of it, wasn't under 2 hours in total exposure. The trick is to take plenty of light frames and to take a fair quantity of dark frames. When I was using my 350D, I'd take at the bare minimum, an hour's worth of darks. I'm not the best imager out there, (though, my aim is to try to be the best with what I own), my ISO-400 images look quite nice (at least I think so!) and print rather well.

Horses for courses. If Duncan owned a 40D, I'd be suggesting trying between ISO-400 and ISO-800.

When I finally get the chance to put my 5D Mark II towards reflection nebulae and clusters, and my modified 40D for everything else, I'll still be sticking to ISO-400 for that smooth, clean look.

Regards,
Humayun

[Hagar]

The way I read this and I may well be wrong is , "you own a 40D and it's diferent." If this is the case I can assure you all my earlier work was done exclusively with a 350D at ISO 800. ISO 800 was selected after quite a bit of testing which indicated exactly what was mentioned earlier. Reduced exposure time = reduced heat = reduced Dark noise.

Naturally the whole requirement is to lift the signal level above the noise to give enough data to smooth out the processing. There will always be a point in every camera where gain/ISO will produce diminished returns on S/N but at 800 ISO and subs below 10minutes this is not the case. The 350D did suffer quite a bit from an amp glow problem but either a great arrray of darks or a minor adjustment in framing and a small crop usually fixed this problem.

At Duncans stage of imaging he needs as much good Signal as he can get to allow his processing skills to climb the tall ladder you and I know exists. That being the case I would strongly urge him to stick with ISO 800, keep his exposure times down around 5 to seven minutes and take lots and lots of them and do like wise with darks, flats and bias frames and he, and we will see a marked improvement in his skills.

[toryglen-boy]

Thanks for info guys, so what exposure what you recommend before noise becomes an issue? at either ISO400 or 800

I supopse you would need a summer max exposure, and a winter one


;)

[Hagar]

My recommendation ISO 800, keep exposure times to 5 or 7 minutes Max and take manual darks and in all cases take lots of them. Take at least as many darks as lights and aim for between 10 and 20 of each. Also worth allowing 30 seconds between frames to allow the CCD to come to thermal equalibrium or as close as you can. This delay between shots makes a diference also.

It will make imaging and processing sessions longer but the results will be stunning.

[toryglen-boy]

hmmm ...

maybe i could just spend a night inside, making a library of darks, so i dont have to do them all the time?

I mean, i know they have to be at the same temps roughly, to if i take some 5 min flats, dump the first one, and just keep a batch of them in a folder, then i should be able to use them as required?

:)

[tlgerdes]

Hi Duncan,

What format are you saving out of DSS, I find the default 16bit format gives washed out images like yours. I manually save to 32bit Rational TIFF.

I have attached the same picture saved as 16bit TIFF and 32bit TIFF from DSS. I have then used PS to only down size and convert to JPEG. Look at the image information difference. For DSS I used MEDIAN as the stacking process. I have tried all variations with the same raw data and I cannot notice any real improvement with the data I use.

These pictures also started life as Canon Raw from a 1000d.

[toryglen-boy]

Hi Trev

Which picture is the 16b and what one is the 32b ?

[White Rabbit]

Hi duncan.

Heres the image, if doing this is wrong ie changing the white balance please chime in and let me know but it seems to work for me. I'm at work atm moment so normally I'd spend a bit more time with it....If you click on the button that says Tune that will bring up the colour palate.

Btw, what are you using to process?

Sandy

[White Rabbit]

the one on the left is the before.

[White Rabbit]

How do you save them as 32bit tiffs I cant find the setting anywhere.

Thanks
Sandy

[toryglen-boy]

I think Trev means after the image is stacked, there are options for saving the final image

Thanks for the image with the colour balance, much appreciate.

:thumbsup:

[White Rabbit]

Yeah I just got it thanks. The median thing seems to work btw, not washed our at all.

[Octane]

Duncan,

I'll probably get shot down for this, but, I'd advise against going down the path of creating a library of darks -- the dynamics of your sensor vary depending on a number of variables (temperature/humidity, et. al.) and no matter what you do, you won't be able to recreate the same characteristics, weather-wise, as when you were out imaging. You will inevitably gain hot/dead/stuck pixels over time. If you owned a good quality CCD, it's a different story, you could probably get away with a library of darks with controlled temperature.

Of course, this all hinges on how accurate you want to be and how much effort you want to put into your images (do you want to be able to print them and hang them on the wall?). I don't necessarily agree with the whole starting-out-so-take-it-easy approach. My personal way of doing things is to do them properly (or to the best of my ability) the first time. Throw yourself in the deep end and learn how to swim. I get a lot more out of it this way. I know it's different for everyone.

Imaging is like climbing a mountain, it's not easy.

My $0.02 AUD, only.

Regards,
Humayun

[toryglen-boy]

no mate, i can see your reasoning, thats some good advice.


:thumbsup:

[tlgerdes]

Yes as Dunc said, once you have stacked the final image, by default it creates AUTOSAVEXXX.TIF. This is saved as a 16bit TIFF file, if you then hit the "Save Picture to File" link in the Processing menu frame you can save the file as a new name and select a different format to save in. Photoshop prefers 32bit Rational TIFF, if you select Integer it will not read.