This is odd... dss problem please help

[Sir Canon]

two nights ago i imaged m42 b33 ngc 1973 and ncg 2024. i did about 20x5sec 15x15sec 20x30sec 15x75sec and 2x120 sec f5.0 iso 1600. i fed dss all the non blurred files and went into pixinsight. after performing just a screen transfer function, this is what came out. what do you think caused all the noise please help,

Thanks,

judson







--
I tend to overdo things

 

[sharkmelley]

It looks like a combination of two problems.

The most noticeable problem is vertical banding, typical of many Canon cameras. There is also some horizontal banding.

The second problem is one often referred to as "walking noise" where a slight drift from frame to frame causes hot pixels to drift across the image leaving noisy trails. This appears to happen in an almost vertical direction but leaning to the right as it goes up.

You don't say if any calibration frames (darks, flats, bias) were used.

Mark

 

[Sir Canon]

this is without dark frames. took some dark's and stacked it again but it looked the same

 

[swimswithtrout]

It's not DSS. Your sub exposures are way too short for f5 with a little kit zoom, as well as your total integration time, barely 1/2 hr, and to top it off, you're trying to stretch it FAR too hard. The result, classic "Canon Banding" .

Try shooting ~ 60, 30 sec subs, and 30-60, 120 sec subs next time and skip all of the rest.

 

[sharkmelley]

I can see why you took a combination of short exposures and long exposures. The short ones to prevent the core of the Orion Nebula burning out and the long ones to reveal the faint details.

However, DSS won't know how to combine them in an optimal way - the shorter exposures are probably the ones with the worst banding. Try making 4 separate stacks - 5sec, 15sec, 30sec and 75sec exposures. Then see if you can selectively merge them in Photoshop using some kind of masking to select the best parts of each of the 4 images.

Mark

 

[Sir Canon]

thanks!

 

[Sir Canon]

so i just need more exposure time. thanks!

 

[rnclark]

so i just need more exposure time.

Looks like you have plenty of exposure time for a great image. You just need better processing.

 

[Sir Canon]

thanks, but when it try to do any processing this banding starts to come up, im trying to avoid that and have the faint diffuse nebula in that region come up

 

[rnclark]

thanks, but when it try to do any processing this banding starts to come up, im trying to avoid that and have the faint diffuse nebula in that region come up

What camera and lens? How are you converting the raw files? How are you stacking the raw files? Any dark frames?

 

[Sir Canon]

this was shot with the canon 550d and a canon 75-300 lens at 7.1 the first exposures were at 5.o but i stoped down a stop and lengthened the exposures to compensate. i stacked these in dss then started to process in pixinsight ind got this result. some stretching and lp subtraction in photoshop yielded the same result. i restacked it with dark frames i took also, and got an almost identical result.

 

[rnclark]

this was shot with the canon 550d and a canon 75-300 lens at 7.1 the first exposures were at 5.o but i stoped down a stop and lengthened the exposures to compensate. i stacked these in dss then started to process in pixinsight ind got this result. some stretching and lp subtraction in photoshop yielded the same result. i restacked it with dark frames i took also, and got an almost identical result.

Did you try raw conversion in photoshop using settings like I show in Figure 2 here:

Astrophotography Image Processing 2, Clarkvision.com

(note, tune the setting in the panel "remove Chromatic Aberration" to your lens.)

Result should be 16-bit tif files.

Then when you stack, color should not change; the ONLY effect of stacking should be less noise.

You should have 4 stacks, one for each integration time.

Roger

 

[Sir Canon]

are you applying the raw conversions to each inage indevuidaly

 

[Dogglet]

this was shot with the canon 550d and a canon 75-300 lens at 7.1 the first exposures were at 5.o but i stoped down a stop and lengthened the exposures to compensate. i stacked these in dss then started to process in pixinsight ind got this result. some stretching and lp subtraction in photoshop yielded the same result. i restacked it with dark frames i took also, and got an almost identical result.

Did you try raw conversion in photoshop using settings like I show in Figure 2 here:

http://www.clarkvision.com/articles/astrophotography.image.processing2/

(note, tune the setting in the panel "remove Chromatic Aberration" to your lens.)

Result should be 16-bit tif files.

Then when you stack, color should not change; the ONLY effect of stacking should be less noise.

You should have 4 stacks, one for each integration time.

Roger

For Roger :

(Sorry to hijack this, Sir Canon, but it's still related. )

With 4 sets of lights at different exposures, and to produce 4 separate stacks, does this mean that we feed in the separate light sets individually to produce its corresponding Autosave TIF. So at the end, we'll have Autosave, A..1, A..2 and A..3 with their corresponding Masters? And if so, would we then still continue to use DSS with these Autosaves and Masters altogether? Or is is totally wrong and we do it another way?

Thanks

 

[sharkmelley]

For Roger :

(Sorry to hijack this, Sir Canon, but it's still related. )

With 4 sets of lights at different exposures, and to produce 4 separate stacks, does this mean that we feed in the separate light sets individually to produce its corresponding Autosave TIF. So at the end, we'll have Autosave, A..1, A..2 and A..3 with their corresponding Masters? And if so, would we then still continue to use DSS with these Autosaves and Masters altogether? Or is is totally wrong and we do it another way?

Thanks

I can answer that - I've done it quite frequently.

It's possible to selectively merge them in Photoshop using some kind of masking to select the best parts of each of the 4 images. However, my preference is to use PixInsight to do an HDR merge automatically - it's called HDRComposition.

If you didn't use the same reference frame for aligning all four stacks then you'll first need to align the 4 "Autosaves" before combining them. It's preferable to use the same reference frame for all 4 stacks but I don't know if DSS can do this (I don't use DSS).

Mark

 

[Dogglet]

I can answer that - I've done it quite frequently.

It's possible to selectively merge them in Photoshop using some kind of masking to select the best parts of each of the 4 images. However, my preference is to use PixInsight to do an HDR merge automatically - it's called HDRComposition.

If you didn't use the same reference frame for aligning all four stacks then you'll first need to align the 4 "Autosaves" before combining them. It's preferable to use the same reference frame for all 4 stacks but I don't know if DSS can do this (I don't use DSS).

Mark

Thanks for the reply, Mark. This complicates things a bit since I just use CS2 for my post processing, and I don't even know if it can handle the masking thing that you mentioned.

About the alignment frame, I think I'm totally lost here. Within a single stack of frames in DSS, sure, I could use any of the frames I like to be the reference frame. But after producing 4 stacked images, I don't have access to the individual frames anymore? Or could I just open the 4 stacked images in DSS, and use any 1 of them as the reference?

 

[sharkmelley]

I can answer that - I've done it quite frequently.

It's possible to selectively merge them in Photoshop using some kind of masking to select the best parts of each of the 4 images. However, my preference is to use PixInsight to do an HDR merge automatically - it's called HDRComposition.

If you didn't use the same reference frame for aligning all four stacks then you'll first need to align the 4 "Autosaves" before combining them. It's preferable to use the same reference frame for all 4 stacks but I don't know if DSS can do this (I don't use DSS).

Mark

Thanks for the reply, Mark. This complicates things a bit since I just use CS2 for my post processing, and I don't even know if it can handle the masking thing that you mentioned.

See a tutorial here on the kind of thing I mean:

Loading…

www.astropix.com

About the alignment frame, I think I'm totally lost here. Within a single stack of frames in DSS, sure, I could use any of the frames I like to be the reference frame. But after producing 4 stacked images, I don't have access to the individual frames anymore? Or could I just open the 4 stacked images in DSS, and use any 1 of them as the reference?

What I've described may not be possible in DSS. You could always align the 4 stacked images in Photoshop.

Mark

 

[Jon Rista]

thanks, but when it try to do any processing this banding starts to come up, im trying to avoid that and have the faint diffuse nebula in that region come up

--
I tend to overdo things

Swimswithtrout is correct, you just didn't use long enough exposures to stretch this image that deeply. You could overcome that by stacking considerably more sub frames, but because of the way read noise compounds through an integration, you really want to take longer subs to pull out the background details best.

Your longest were 120 seconds, it seems? You only had two of those, which just isn't enough, but even if you had say 16, you probably wouldn't have quite enough to eliminate the banding. You probably need to go longer than that. At f/5, you probably want 360 second subs for your longest subs. I say that, because I used 270 second subs at f/4 with a 150mm aperture on this image:



This was also at a pretty dark site. If you are in a more light polluted zone, then you may be limited in how long you can expose, and if you are in a heavily light polluted zone, your only option will be to integrate LOTS of shorter subs. Based on your 2x120 integration, you seem to have reasonably dark skies, so I would try for a longer set of subs, 270, 300, or 360 seconds, and see how that goes. Also, get a lot more than just 2.

 

[Sir Canon]

thanks, im going to go for some longer exposures when it clears up, Btw will more exposures make the details more crisp like in your photos because i am constantly having images that look "soft" even though it is perfectly in focus

 

[jammeymc]

I had this happen to me one time, and one time only. I was shooting M45 shortly after it came up over the east Horizon, for about an hour. I did everything as i normally did. I believe i was shooting 30 second frames. I, for the life of me, do not know what caused it. However, i think shooting M45, through all the LP as it was rising from low to the horizion had a lot to do with it.....essentially shooting through a lot of faint haze via that angle. I decided that i would never shoot at that angle again and thus I have never had this happen again either! Unscientific but that's my guess.