Noise!!!!!!!!!!!

[raymo]

As my early efforts have all been short subs, generally up to 30secs, I
have been able to control noise using my very limited processing
ability. Now I have better PA I am using subs of 60, 90, and even 120secs.The noise I am seeing at those sub lengths is absolutely
horrendous, especially considering that the ambient has fallen to
around 12-14 degrees, and I am using 400 and 800 ISO. I haven't
got one useable sub over 60 secs. I took a single wide angle sub
of the LMC last week with my 18-55 lens of 50 secs. It was appalling.
Unless some one can tell me what I am doing wrong, or how to get
some control of noise, I'm going to have to resort to huge numbers of
subs at 30secs or so. It"s made worse by the fact that when posters
talk about using noise reduction features, I have no idea what they are talking about. I can't find any tools related to noise in my version of
PS [PS7]. Neatimage seems to help a bit, if you don't overdo it.
HELP!!!!!
raymo

[pluto (Hugh)]

Are you taking multiple subs and stacking them?
That should fix a lot of the noise. Also stacking with dark frames helps heaps too.

As for removing noise during processing, the best by far I have found is the noise reduction in Lightroom.

[traveller (Bo)]

Download Deep Sky Stacker (free) and use it to your hearts content...

[raymo]

Thanks Hugh and Bo. I already use DSS and stack up to 70 subs at a time. I use in camera noise reduction, so I am getting an equal number of darks, and hence don't get any hot pixels. Iwill have a look at lightroom.
Thanks raymo

[alistairsam]

hi Ray,

do you know what the temperature of the sensor was when you took these subs apart from ambient temperature? Are you able to post one of the raw subs here?

I took 5 minute exposures last night at iso800 using my unmodded uncooled 1000d, wasn't too bad. sure there was noise, but not unmanageable. so there might be something wrong or it must've been a pretty warm night.

when you say noise, are you referring to the coloured specks or pixels all over the image? The in-camera noise reduction is normally quite effective. you mention that you can't see any hot pixels, but in the stacked image, you see a lot of noise? is this correct?

To effectively remove noise with darks, you need to dither the frames. not sure what software you're using for scope control or are you using the hand controller?
you usually enable dither in your main capture software that can talk to the mount and its usually done via the guider. the software will move the scope one or two pixels between every frame, but since you're not guiding, I'd suggest manually nudging the scope a tiny bit every few subs.

That way, DSS or other software will see the noise as a fixed pattern which hasn't moved and subtract it.
have you tried taking a dark and stretching that to see how much noise you have?

if you can't post a raw sub, can you take a screenshot of what you see when processing and post that?

Have you looked at software like BackyardEOS? makes capturing images very easy and its relatively inexpensive. It has a plugin for phd dither, but that's for when you start autoguiding.

Cheers
Alistair

[pluto (Hugh)]

I think you'll get better results if you disable in-camera dark frame subtraction and take dark frames to stack in DSS. That way each light frame will have the noise of all dark frames subtracted instead of only one dark frame per light frame.

[raymo]

Hi Alistair, I am not at home at present, and my images are on my laptop
there.I have recently bought BackyardEOS but haven't had time to get into it; hopefully next week, weather permitting. Because my PA is not perfect I can see slight movement of the target from one sub to the next
when viewing them on the camera's screen, so I thought that would take care of dithering. I have no idea how one would know the sensor temp.
The ambient recently has been 12-14 degrees. I don't use raw at all, just
stick to JPEGs [I know raw is better]; I'm just so sick of constantly
having to find ways of changing file types to suit software needs. Even
video files from my Canon are not recognised.
Just seen your post Pluto; I will try that, thankyou.
The noise I see is usually in the form of horizontal lines of fluffy knitting,
[that's the best description I can think of]. Sometimes it is like tiny
clouds of a combination of grey and pink. Another member recently
posted that he had the same horizontal lines in his images using his
1100D, so I assume that it is normal. I think that my main problem is that as an oldie I have little empathy with computers, and am in
totally alien territory. As an example, I can take a dark, as you suggest,
but as to how to stretch it to see how much noise I have, I wouldn't
have a clue. As fast as I learn how to do something, the next something turns up. You may usually get better results than film gave, but my
goodness you have to work for it. This is my last attempt to get it all
together. It is stupid and pointless receiving all this wonderful help
and advice, and wasting people's time, if it is just too much for me.
Thank you all so much.
raymo

[rustigsmed (Russell)]

Hi Raymo, i think you are already using DSS to stack your images?

The easiest thing to do would be to take some darks. Just put the lens cap on or the scope dust cover and shoot about 10 - 20 shots with the same exposure length and iso that you have been using.

Thats all you need to do. When going into DSS, you have to select your light frames as usual, the only extra step is to select your dark frames too. Then let the program do its thing. It will automatically make a 'master dark' which you can use for a few months (or simply select the frames again for the next target you use).

cheers

Rusty

[tilbrook@rbe.ne (Justin Tilbrook)]

Hi Raymo,

Turn off live view when imaging.
With live view on the censor runs at nearly 40c on a night that's around 17c.
This will also get rid of the lines in the image.

Cheers,

Justin.

[pluto (Hugh)]

You should definitely shoot raws, DSS will stack Canon raws so you you won't need to deal with converting them.

[raymo]

Thankyou Rusty, Pluto, and Justin. Justin, to clarify what you have said;
I gather you mean stop the camera displaying the image after taking the sub. The only time I use the actual Liveview feature is for initial focusing with my Bahtinov mask. The image is only displayed for about half a second or so before I take the next sub. I have now realised that a sensor
cooling period should be allowed between subs, maybe 10 secs or so.
Pluto, I am aware that DSS is happy with raws, but my comp won't open
them when they are put in a file, so I still end up having to convert them. If I remember rightly, I don't think my PS accepts them either.
Does simply having Liveview selected cause any heat increase, or does the screen have to be actually illuminated?
raymo

[traveller (Bo)]

Backyard eos has a focusing function which I use over the live view function as it is more sensitive in my view.
Re taking darks, make sure you select the dark frame selection in backyard eos so the program is not thinking it is a light frame.
I also cool the camera in the fridge and wrap the camera in a plastic bag and put ice packs over the camera when aquiring dark frames to keep them around 5-7c. Not sure if it's the right thing to do but sure cuts down on the noise.
Bo

[raymo]

Thanks Bo.I had noticed the focus function in my look through Backyard, and planned to use it. I had thought about the fridge, but had read posts saying that the camera mirror fogs up. I also thought that the benefit
might be limited as the camera would warm up significantly over an
imaging session, but I suppose you could do several short sessions rather than one long one, and put it in the fridge between sessions.
raymo

[pluto (Hugh)]

Originally Posted by traveller

Backyard eos has a focusing function which I use over the live view function as it is more sensitive in my view.
Re taking darks, make sure you select the dark frame selection in backyard eos so the program is not thinking it is a light frame.
I also cool the camera in the fridge and wrap the camera in a plastic bag and put ice packs over the camera when aquiring dark frames to keep them around 5-7c. Not sure if it's the right thing to do but sure cuts down on the noise.
Bo

The dark frame selection in BYE just changes the file name, AFAIK it doesn't change anything else.

You want your dark frames to be at the same temperature as your light frames. If you are taking your darks at a lower temperature than your lights then they will have less/different noise and you won't get as much benefit when stacking. If the temp is drastically different then it may make your stack worse than if you didn't use them at all.

[raymo]

At least by using the in camera noise reduction I know the temp will be the same.
raymo

[Oggie (Peter)]

Originally Posted by raymo

Pluto, I am aware that DSS is happy with raws, but my comp won't open
them when they are put in a file, so I still end up having to convert them.

I think this can be fixed by installing the free Canon Raw Decoder from Canon's site: http://support-au.canon.com.au/conte...200255003.html

[raymo]

Thanks Peter, I'll do that.
raymo

[jsmoraes (Jorge)]

Up to now I only work with DSLR Canon. Model 350D. My sessions have around 30 - 50 minutes. Depend of which battery I am using.

My experience says:

1) dark frame: I use only 5 or 10 as normal photo. Same ISO and exposure. It is captured after de session. They will used in DSS as dark frame.

2) The native ISO of 350D is 800. I work with this ISO or less: 400 and 200. ISO 1600 the noise is absurd.

3) the time of exposure is 240 sec maximum (4 minutes). Because of light pollution,the glow of background is very high if I use more time. And they are sequencial: there are no time between them.

4) if the seeing is bad, I perceive that the noise is more strong. Please don't ask me why. As I told ... I perceive.

5) I don't use the internal Canon noise filter. I don't see high improvement on the result.

6) I never perceived difference in intensity of noise of first frame and the last frame.

6) After stacking with DSS, I don't make any adjustment. I use the original Autosave.tif - 32 bits. In Photoshop I convert it to 16 bits, using the Local Adaptation option, and make adjustments with the HDR curve. Radius: 1 or 2 px and Threshold 0,50 or less.
This conversion can increase the noise. You must experiment to get the better image: details versus noise.

7) to reduce the noise, I use in photoshop noise reduction in each color channel. My camera has more noise in red. The minor noise is in green.
There are no trick to it. Some times I create mask of background. Some times not. Each case is a different case.

8) Some times to the final work I use Filter blur -> surface blur (radius = 2 or 4 and threshold never more than 4) , noise -> dust & scratches (raise = 1 threshold = 1 and opacity layer less than 50 %)

You can check my photos in astronomia.pousadavilatur.com.br. My great problem is focus, because 350d hasn't live view.

[traveller (Bo)]

Originally Posted by pluto

The dark frame selection in BYE just changes the file name, AFAIK it doesn't change anything else.

You want your dark frames to be at the same temperature as your light frames. If you are taking your darks at a lower temperature than your lights then they will have less/different noise and you won't get as much benefit when stacking. If the temp is drastically different then it may make your stack worse than if you didn't use them at all.

Useful info. Maybe I should cool the camera before taking light frames to match....
Bo

[LightningNZ (Cam)]

My setup is quite unsophisticated (because I am essentially lazy) but I can control the noise from Canon 300D reasonably well if the ambient heat isn't too high.

Here's my general observing session:
1) Take a bunch of light images of between 30 seconds and 2 minutes depending on much effort I've put into polar alignment.
2) Every hour I take 5 or 6 dark frames, so I can at least get the temperatures matched to the light frames. You don't need many dark frames with modern cameras and the 300D is likely the oldest camera you'll see on these forums - it's very badly affected by high temperatures.
3) Once my tiny memory card is full (about 70 images) I take the scope (AT65-EDQ) inside with the camera still attached and pull down all the images to my computer.
4) I take flats by photographing my LCD screen (set to white) at close range. I take maybe 20-30 flats and move the scope/camera setup around as I do so to even out any imperfections in the LCD panel.
5) Run it all through DSS, saving the resulting file as TIF (no file compression, no losses).
6) Post-process in Photoshop.

I think you'll find that if you turn off the built-in noise reduction you'll be able to get a lot more starlight for time outside and the few darks you get will give a smoother result than a single dark per frame.

Hope this helps,
Cam