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Filament-like noise and no details

Ishan Mair

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Ishan Mair

Ishan Mair

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Hi guys,

Last night I shot my second guided image. Its M81 & M82. I am finding it difficult to get the details out of the galaxies. All over the image there are filaments of red and blue noise. Didnt dither. Is it LP or temp(about 22C its never gets cooler than that here) or bad processing or what else?
Am I exposing it too much? Processing was Lev, Curves stretching, Flat field subtraction, NR, Smart Sharpen.

post-26619-0-52438400-1421550744_thumb.j
 

30 x 5 min + 25 Darks +30 Flats + Bias all @ ISO 400 

Canon 1100D, Skywatcher 130PDS f/5
HEQ5 PRO, Orion SSAG, 50 mm guider,

APT, DSS, PS.

This is the histogram of a single sub.[

attachment=148111:Sub_Hist.png]
 

Please help.
Ishan.

post-26619-0-07276500-1421550747.png

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Ishan Mair

Ishan Mair

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Your histogram looks very far to the right. If that is the histogram before processing then you are likely to be clipping data at the White point which will not be helping.

But this is not the linear histogram...I am confused here...Histogram should be 25-30% from left...BUT WHICH HISTOGRAM? Linear or Non-Linear? Back of camera, APT, Canon DPP all show non-linear histogram. Linear histogram is displayed by checking "linear" on DPP Toolbox...The one I posted above is non-linear

Did you shoot these with the camera set to jpeg output? If so, you'll get better results by using RAW. M81 especially looks posterised which is a symptom of insufficient bit depth.

Regards

Andrew

Whats the best way to "use" a DSS output file in Photoshop?

Thanks,

Ishan.

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andrewluck

andrewluck

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Dithering is a must for reducing noise but  I suggest re-stacking without calibration frames and see if the image looks any better from a noise point of view.

The ideal file to edit in Photoshop is a 16-bit tiff. Then , as Frugal suggests, don't clip the highlights and, at least initially, don't clip the blacks. Leave the image as 16 bit all the way through processing until you're ready to export a jpeg for the web.

Andrew

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Ishan Mair

Ishan Mair

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Thanks Andrew. 

I tried stacking only light frames..maybe a little better from a noise pov. But yet I am not able to pull out any details. Here is a  crop of the stacked tiff image with the two galaxies...https://www.dropbox....2_Crop.tif?dl=0

It would be great if someone tries to process it.

Just in case it is useful the image resolution is 1.67 arcsec/px.

Ishan.

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Uranium235

Uranium235

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Assuming calibration was done properly (darks, bias and flats) - then it looks as though you have run into a bit of chromatic noise, which is the achilles heel of the DSLR. Chromatic noise takes the form of blotches or background colour in places that should be empty space (black-ish). Noels "deep space noise reduction" action can fix this to a degree, but if you really want to reduce it (cant be totally eliminated) then you need longer subs (10 or 15min), and more of them. No need to bin what you have, just throw a lot of long ones on the pile.

Also, run at ISO800 - it has less read noise than ISO400.

Additionally, take a look at the LLRGB method of processing DSLR data, ie: Using a mono version as lum (helps with the noise), then pasting in the colour as a separate layer.

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Ishan Mair

Ishan Mair

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Link is broken...

Sorry for the link..I fixed it here  https://www.dropbox.com/s/xn50ixc1vks5pd6/Crop.tif?dl=0

Assuming calibration was done properly (darks, bias and flats) - then it looks as though you have run into a bit of chromatic noise, which is the achilles heel of the DSLR. Chromatic noise takes the form of blotches or background colour in places that should be empty space (black-ish). Noels "deep space noise reduction" action can fix this to a degree, but if you really want to reduce it (cant be totally eliminated) then you need longer subs (10 or 15min), and more of them. No need to bin what you have, just throw a lot of long ones on the pile.

Also, run at ISO800 - it has less read noise than ISO400.

Additionally, take a look at the LLRGB method of processing DSLR data, ie: Using a mono version as lum (helps with the noise), then pasting in the colour as a separate layer.

Thanks Rob, but I have a question.. Wouldnt the ISO 800 and/or longer subs put the histogram too much to the right? (Please see my previous post about histogram in this discussion.) Looks like I do need a LP filter now...I have downloaded a video tutorial by Scott Rosen for LLRGB processing..

Ishan.

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andrewluck

andrewluck

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What do you think?

post-26516-0-88462800-1421758051_thumb.j

This is the result of some fairly heavy noise reduction in Pixinsight followed by some masked stretching and colour saturation to enhance the galaxies. M81 is particularly tricky as the arms are very low surface brightness and are barely above the noise.

Full size tif here: https://www.hightail.com/download/UlRUaUNPZDU5NVdybHNUQw

Regards

Andrew

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Ishan Mair

Ishan Mair

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What do you think?

attachicon.gifCrop-PI.jpg

This is the result of some fairly heavy noise reduction in Pixinsight followed by some masked stretching and colour saturation to enhance the galaxies. M81 is particularly tricky as the arms are very low surface brightness and are barely above the noise.

Full size tif here: https://www.hightail.com/download/UlRUaUNPZDU5NVdybHNUQw

Regards

Andrew

Thank you so much Andrew..Its on another level as compared to mine..

I need more integration time or a dark sky. The dust mote on bottom-left indicates flats arent working...I've got a lot to sort out!!

Thanks for the help everyone,

Ishan.

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