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20 hours ago, Rodd said:

Now that you mention this I took a closer look at the background and see what you mean.  Its always something.  Your processing skills have almost eliminated the pattern.  

Rodd

It is getting there.  I will try again with just proper dithering and see what I get.  Although I suspect I may need to go back to using darks to get rid of the small amount of amp glow.

My suspicion is that the D7500 does not have any more amp glow than my old D5300 but because the D7500 has overall a great deal less noise, the amp glow is more noticeable.  A few more experiments should tell the tale.

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13 hours ago, Stub Mandrel said:

Lovely image - almost as much detail in your tags too :icon_biggrin:

:)

Pathetic, I know but I like it when the search engines can find my images :icon_redface:

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1 hour ago, MikeODay said:

:)

Pathetic, I know but I like it when the search engines can find my images :icon_redface:

You'll fine a shorter list of more precise tags, three to five, will rank a lot higher in search results.

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Mike,

I had a go at the background with a new plug in filter I just bought for PS called Neat Image. It did quite a good job ( I used layer masks and the brush to protect the galaxy). Here it is before and after:

Cheers

Göran

MikeOdayNGC1365.jpeg

MikeOdayNGC1365 GN.jpg

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9 hours ago, Stub Mandrel said:

You'll fine a shorter list of more precise tags, three to five, will rank a lot higher in search results.

Cheers Neil

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4 hours ago, gorann said:

Mike,

I had a go at the background with a new plug in filter I just bought for PS called Neat Image. It did quite a good job ( I used layer masks and the brush to protect the galaxy). Here it is before and after:

Cheers

Göran

 

 

Thanks Goran for going to that effort; it seems to work very well, I will keep it in mind if I can’t get rid of the pattern at the source.

Cheers

Mike

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12 minutes ago, MikeODay said:

Thanks Goran for going to that effort; it seems to work very well, I will keep it in mind if I can’t get rid of the pattern at the source.

Cheers

Mike

Yes, going for the source if of course the best. I have had similar patterns in some of my DSLR images and I have wondered if it could be the shutter that makes the set-up shake a tiny bit and the image to shift very slightly between frames creating that banded noise after stacking. Like a natural dithering but unfortunately only in one direction.

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7 minutes ago, gorann said:

Yes, going for the source if of course the best. I have had similar patterns in some of my DSLR images and I have wondered if it could be the shutter that makes the set-up shake a tiny bit and the image to shift very slightly between frames creating that banded noise after stacking. Like a natural dithering but unfortunately only in one direction.

That sort of diagonal 'brushed' pattern often gets called 'walking noise' but I have it very clearly in some data from guided subs where all the subs are perfectly aligned on the sensor so it can't be 'walking noise'. I am now convinced it is caused by high, thin cloud or haze and the direction of the texture matches the drift of the cloud.

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3 minutes ago, gorann said:

Yes, going for the source if of course the best. I have had similar patterns in some of my DSLR images and I have wondered if it could be the shutter that makes the set-up shake a tiny bit and the image to shift very slightly between frames creating that banded noise after stacking. Like a natural dithering but unfortunately only in one direction.

In my case I know why I have streaks ...

A single image ( dark or light ) shows no signs of pattern in the noise.  However, when I stack a number of dark images the very low level of pattern noise ( including amp glow on the left ) starts to be seen.  Overall the noise is quite low, and the pattern noise even lower, but when I stacked 70 lights to get the image above and then performed a very strong stretch to bring up the faint arms, the amp glow and pattern noise became quite visible.  The reason there are streaks from the pattern noise is that I messed up dithering; in effect I was dithering in an almost constant shift in one direction rather than the random pattern I had intended.  Dithering will be the easiest part to fix and I am keen to see if doing so will be enough to minimise the pattern noise in the main part of the image.  I will have to try harder with the amp glow; I want to avoid darks if I can because of the additional noise they introduce, so my first plan is to double check that I have turned off every function in the camera that might be drawing current during capture.  

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4 minutes ago, Stub Mandrel said:

That sort of diagonal 'brushed' pattern often gets called 'walking noise' but I have it very clearly in some data from guided subs where all the subs are perfectly aligned on the sensor so it can't be 'walking noise'. I am now convinced it is caused by high, thin cloud or haze and the direction of the texture matches the drift of the cloud.

You may well be right about the cloud and in my case it may have also contributed ( albeit that I don’t think it was the primary cause ).  I will know more when I get a chance to get back out and take some more shots.

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1 minute ago, MikeODay said:

You may well be right about the cloud and in my case it may have also contributed ( albeit that I don’t think it was the primary cause ).  I will know more when I get a chance to get back out and take some more shots.

It's possible/probable that some of these effects have multiple causes.

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Very very good image, that type of noise (whatever the cause) is normally dealt with by a larger scale dither to your subs. 

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13 hours ago, Adam J said:

Very very good image, that type of noise (whatever the cause) is normally dealt with by a larger scale dither to your subs. 

Thanks Adam.  I will try increasing the dither size next time.

Cheers

Mike

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In his book of observations from the Cape of Good Hope, Sir John Herschel included a number of sketches of the more interesting objects.  The Great Barred Spiral Galaxy ( NGC 1365 ), as it known now, was recorded by Herschel as # 2552 in his book and below is the sketch made from his observations of this “nebula” in late November of 1837:

9E71A38A-184C-4D01-A474-7A7E439EBBEE.thumb.jpeg.744dfaf12276d4663201b49ee2638ec2.jpeg

“The Great Barred Spiral Galaxy ( NGC 1365 )” as shown in figure #1, plate iv, from Sir John Herschel’s book of observations from the Cape of Good Hope.  From Observations on the 28/29 November 1837 made with his 20’ focal length Newtonian reflector.

c.f.

C0C5B60D-3E4B-4402-BC0A-C202DE096810.jpeg.60dfc5fe50db0ca5bc9a17192846d22f.jpeg

Edited by MikeODay
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12 hours ago, Allinthehead said:

That's a great image Mike.

Thanks, much appreciated.

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What a fantastic amount of detail!!! Well done, it's a master piece... definitely a great barred spiral galaxy pic.

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On 10/12/2017 at 22:07, kirkster501 said:

A great picture, I love the detail you’ve got inside the galaxy.

 

On 11/12/2017 at 23:52, MarsG76 said:

What a fantastic amount of detail!!! Well done, it's a master piece... definitely a great barred spiral galaxy pic.

Thanks guys, much appreciated.

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The Great Barred Spiral Galaxy ( NGC 1365 ) in the constellation Fornax

New version with new long exposure data ( 52 x 240sec ) and better dark subtraction / dithering to remove streaks in the noise and amp glow.  This also allowed for a greater stretch revealing more faint data in the galaxy and small faint fuzzies in the image ..

7F1F55D3-C8E6-44EA-B071-9E90EAA9A934.thumb.jpeg.f079ef12e386988d368c3c1c2bb97074.jpeg

The Great Barred Spiral Galaxy ( NGC 1365 ) in the constellation Fornax ( please click / tap image to see larger )

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Excellent image. The added data made a huge improvement of what already was a great image.

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10 hours ago, wimvb said:

Excellent image. The added data made a huge improvement of what already was a great image.

Thanks Wim, much appreciated.

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On 25/12/2017 at 19:34, MikeODay said:

The Great Barred Spiral Galaxy ( NGC 1365 ) in the constellation Fornax

New version with new long exposure data ( 52 x 240sec ) and better dark subtraction / dithering to remove streaks in the noise and amp glow.  This also allowed for a greater stretch revealing more faint data in the galaxy and small faint fuzzies in the image ..

 

The Great Barred Spiral Galaxy ( NGC 1365 ) in the constellation Fornax ( please click / tap image to see larger )

100% crop of new version:

ED66B08E-C020-492C-A2B1-A69A6EAA2989.thumb.jpeg.caa902c74343985a797368d7649c74f4.jpeg

The Great Barred Spiral Galaxy ( NGC 1365 ) 100% crop ( please click / tap image to see larger )

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Lovely shot Mike.

This is one of my favourite galaxies. Shame its to far South for us here in Europe.

Tom

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