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Strange colour and weird background noise


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Hi guys looking for some help .

I just got back into this imaging and I've come up against a strange effect .

I'm using a dslr nikon d90 and after taking approx 200 shots and all the flats darks etc once its gone through dss and them stretched in pixinsight it leaves a lot to be desired whstvi have is this .

I think its amp glow but I'm not sure 

Any help would be good .

Thanks in advance fellas I'm sure you know where I'm going wrong.

Best regards Barrie 

 

20210301_001056.jpg

Edited by barrie greenwood
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  • barrie greenwood changed the title to Strange colour and weird background noise

the walking lines are from the static noise in the image staying in the same place, to remove this you need to dither your image and then it gets processed out in stacking but dont know about the colour issue

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5 hours ago, Iceman120 said:

the walking lines are from the static noise in the image staying in the same place, to remove this you need to dither your image and then it gets processed out in stacking but dont know about the colour issue

Never had this before nor had to dither as I'm not sure how to .

This was taken using to same set up with no issues I'm wondering if it's light thstd got into the scope or high level cloud  playing havoc with it seems strange I've never had this before at all 

Image33_DBE coloured copy copy.jpg

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1 hour ago, barrie greenwood said:

This was taken using to same set up with no issues

I think if you stretch this image the same as the Flame image you'll see the same problems. 

Dave.

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What I was meaning, in way too few words I'll admit, is that you don't have a new problem.

The M42 image has a lot of black clipping and is therefor hiding the streaks that are evident in the Flame image. I downloaded your image last night and checked.

The circular colour issue has been discussed on this forum before but I don't know where it is now.

Good luck,

Dave.

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1 hour ago, michael8554 said:

I agree with Dave.

You've crushed the walking noise into the black in the second image, it's there like the Horsehead image, though a screen shot doesn't help all that much.

Hi guys thanks. 

Ok I don't know how you mean by crush into the black. 

How does this happen is it in capture or process or is an issue with equipment. 

Please forgive my ignorance but its a new one on me and after stopping up till 3am processing it all again etc I deleted all the data thinking it was no good .

Regards Baz 

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When you clip or crush the blacks what you are doing is turning everything from the dark end of the image into black. This includes dark grey detail unfortunately and is part of processing rather than acquisition. I can't particularly help as I'm not a PI user. There are one or two of us still left I believe :)  

If you look at the histogram for the M42 image you should see quite a bit of information hard up against the left margin so the streaky noise has been supressed and hidden.

But at least I don't think you have a new problem with the camera.

Dave.

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You best option will be dithering the images. Even if you don't guide, some software allows dithering (APT and NINA I think do this). If you are just using an intervalometer and saving in the camera, just shift the image by a few pixels every few frames.

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1 hour ago, Clarkey said:

You best option will be dithering the images. Even if you don't guide, some software allows dithering (APT and NINA I think do this). If you are just using an intervalometer and saving in the camera, just shift the image by a few pixels every few frames.

Ok after reading up on this I get it .

So can anyone point me into the stuff I need to use on my synscan goto to autoguide it ive used my laptop in the past but it did seem hard work to make work is there a stand alone guider available 

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Morning guys. 

I've done loads of reading so I've managed to get my head around it now. 

I've used PhD guiding before but I need to refine my gear to be able to use it properly .

Anyway thanks so much for your help guys so much to learn yet thanks again. 

Regards Baz 

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Just to add to my earlier comment. To manually dither you can just use the hand controller to move the image in the camera a fraction at a time every few frames. This will get rid of the walking noise. If you have dozens of frames you only need to do it every few minutes.

Alternately I would suggest a laptop with some basic control software which can dither for you even without a guider. It will also help with things like focusing and framing.

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22 hours ago, Clarkey said:

Just to add to my earlier comment. To manually dither you can just use the hand controller to move the image in the camera a fraction at a time every few frames. This will get rid of the walking noise. If you have dozens of frames you only need to do it every few minutes.

Alternately I would suggest a laptop with some basic control software which can dither for you even without a guider. It will also help with things like focusing and framing.

I've looked at apt and seen the dither on there but could not work out how to use dither without guiding 

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The APT dithering can be set to adjust the mount only for widefield imaging (I just randomly moves the mount slightly). This avoids the need for a program like PHD2. From the APT manual:

"APT Dithering is special feature made to provide dithering when there is no guiding because your mount is high-end (ASA, 10Micron and etc.) or when you are using short focal length lens or telescope. APT Dithering uses a mount connection to make the needed random position changes between the exposures"

If you go to the APT website you can download the manual and have a look at the functionality.

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There's been a lot of discussion in his thread about the walking noise but none about the coloured rings in the background.  The coloured rings are almost certainly caused by Nikon's lossy data compression.  It's a common problem when imaging with Nikons and it was discussed on a recent thread over on Cloudy Nights:

Nikon Coloured Concentric Rings - DSLR, Mirrorless & General-Purpose Digital Camera DSO Imaging - Cloudy Nights

Mark

Edited by sharkmelley
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1 hour ago, sharkmelley said:

There's been a lot of discussion in his thread about the walking noise but none about the coloured rings in the background.  The coloured rings are almost certainly caused by Nikon's lossy data compression.  It's a common problem when imaging with Nikons and it was discussed on a recent thread over on Cloudy Nights:

Nikon Coloured Concentric Rings - DSLR, Mirrorless & General-Purpose Digital Camera DSO Imaging - Cloudy Nights

Mark

Very interesting article that and yes I can firm its a problem on the other nikons also my d90 being one .

So I always thought the aim was to get as long an exposure as possible to gather more data if I was to keep the histogram in the far left I would have to dial down the iso and drop the exposure time of the lights .

Also interesting is the time I took my lights the moon was up in full not hi but enough to cast a glare so I'm thinking the light pollution is a factor in this as well .

Regards Baz 

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Ok Baz. I think you need to get some basic concepts sorted first. Read "Making every photon count" it will give you a good idea of the principles.

The basic problem is that you don't have enough exposure time. Remember you are capturing photons. There is no such thing as half a photon. To illustrate, imagine the brightest part of the picture captured 10 photons, then you stretch the image so that was the brightest pixel in the image. You can only have 10 levels of brightness. It will look rubbish. So you have to capture as much light as possible. ( Increasing the ISO wont help, it may increase the number in the file but you will still have 10 steps ). If you do a really long exposure you risk all sorts of problems with aircraft, satellites etc. So, you need to do many  exposures and add them together using a stacking program like Deep Sky Stacker. You will find people who do hours of exposure time and they get lovely smooth images with lots of detail.

It's probably not a good idea to do a session when the moon is up, but I know that enthusiasm will get the better of you. By all means do it but don't expect great results. Sometime I do it because I want to try things out and practice is always a good thing.

The issues of noise that you are getting are down to the next level of detail. You need to get some basics understood first. Watch some tutorials, look at peoples results and importantly; how they got them. ie number and duration of exposures ( subs ). You have a reasonable result given what you started with but you need a lot more exposures and a lot more understanding.

Hope this helps. There is a lot to learn.

cheers

gaj

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The flame photo I had the problems with was over 200 stacked 30 seconds exposure photos  if I increase the iso it makes the film faster in old terms catching more photons but adds noise  .

The issues was not the frames themselves but one the walking noise and two the coloured rings .

The walking noise I now understand and someway the coloured rings is an artifact produced in nikon cameras .

To combat the rings which is a nikon camera issue mark says in his article to have the histogram 1/4 to the left in the subs this is what I don't understand as to do that it means shortening the exposure time or dropping the iso both in effect cutting light  the third factor is light pollution, at a dark site I could increase the exposure time without adding as much light from the surrounds which I think would help with the rings from the nikon lossy raw files

Edited by barrie greenwood
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