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MikeODay

IC 4628 ( Prawn Nebula ) in Scorpius ( re-processed )

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Bright Nebula IC 4628 in the constellation Scorpius.

( a re-processed version can be found in a comment below - colour balance tweaked to add a little blue )

( another re-processed version can be seen below - this time to increase the vibrance & saturation somewhat ( too much ? )

image.jpeg

( click on image to see full size )

IC 4628, called the Prawn Nebula by some, is an emission nebula in the far southern sky in the constellation Scorpius. Relatively faint, with a visual magnitude of +10, IC 4628 resides in a rich area of the Milkyway about 6000 light years from Earth.

Links:

https://500px.com/MikeODay

http://photo.net/photos/MikeODay

Details:

centre of image: RA 16h 57m 4s, Dec -40 deg 21' 52" (nova.astrometry.net)f
ield of view: 80 x 53.3 arcmins
Skywatcher Quattro 10" f4 Newtonian
Skywatcher AZ Eq6 GT Mount
Guiding: Orion Shortube 80 guidescope
Starshoot Autoguider, PHD2
Baader MPCC Mark 3 Coma Corrector
Hutech IDAS D1 light pollution filter
Nikon D5300 (unmodified)
Long exposure noise reduction on
32 x 182 sec @ ISO800 (15 May 2016)
Pixinsight

Edited by mike005
a re-processed version can be found in a comment below - colour balance tweaked to add a little blue
  • Like 10

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That's a great image, especially considering that your imaging camera is not modified. And a lot of faint nebulosity as well!

Does the long exposure noise reduction make any difference? I disabled it on my camera, because it takes twice as long to take each sub. (I don't even do darks any more.)

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1 hour ago, wimvb said:

That's a great image, especially considering that your imaging camera is not modified. And a lot of faint nebulosity as well!

Does the long exposure noise reduction make any difference? I disabled it on my camera, because it takes twice as long to take each sub. (I don't even do darks any more.)

Thanks Wim.  I have found that the in camera noise reduction makes a huge difference with the D5300 and more than make up for the fewer lights I can take.. That is, the noise reduciton from in camera dark subtraction is substantially bettter than taking twice as many lights.  I imagine others get this benefit from taking separate darks but I have had no success with using darks - no matter what I do I can not get rid of the 'rain' effect that comes from subtracting a fixed noise image from random noise that is constantly varying as the night progresses.

Cheers

Mike

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Re-processed to tweak the colour balance ( add a little blue ) ...

IC 4628 ( Prawn Nebula ) in Scorpius - by Mike O'Day ( https://500px.com/mikeoday )

 

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19 hours ago, mike005 said:

Thanks Wim.  I have found that the in camera noise reduction makes a huge difference with the D5300 and more than make up for the fewer lights I can take.. That is, the noise reduciton from in camera dark subtraction is substantially bettter than taking twice as many lights.  I imagine others get this benefit from taking separate darks but I have had no success with using darks - no matter what I do I can not get rid of the 'rain' effect that comes from subtracting a fixed noise image from random noise that is constantly varying as the night progresses.

Cheers

Mike

If by "rain" effect you mean streaks in the background, have a look at this:

But I agree, if you can avoid it in the first place, keeping noise reduction on is preferrable. I will test it when imaging season starts again in a few months, it's just that clear nights have been scarce this past season, and I always wanted to gather as much data as possible "between the clouds". But I guess sometimes less is more and more is less.

 

Cheers,

 

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Thanks Wim.

The problem is more as shown in the following thread ...

I have read that the way to overcome this is to apply dithering to the tracking algorithm.  I have not been able to get it to work for me though.  

Cheers

Mike

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Yes, dithering is the way to go. But that won't do you any good on the images you already have. Restacking with careful pixel rejection and noise reduction during post processing can clean up most of this pattern.

Since I don't use guiding, I used to dither manually by pressing the Dec or RA keys on my handset. But I got tired of this eventually and built myself a controller that does the work for me. I programmed it to dither in the spiralling pattern you can see in the video in the post I quoted.

If you google "Tony Hallas astrophotography", you will find a youtube video on the merits of dithering for DSLR astrophotography.

 

Good luck

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I like the image a lot, but cannot see any prawns. Tried looking for a while but just cannot see it at all.

Nice though.

Derek

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21 hours ago, wimvb said:

Yes, dithering is the way to go. But that won't do you any good on the images you already have. Restacking with careful pixel rejection and noise reduction during post processing can clean up most of this pattern.

Since I don't use guiding, I used to dither manually by pressing the Dec or RA keys on my handset. But I got tired of this eventually and built myself a controller that does the work for me. I programmed it to dither in the spiralling pattern you can see in the video in the post I quoted.

If you google "Tony Hallas astrophotography", you will find a youtube video on the merits of dithering for DSLR astrophotography.

 

Good luck

Thanks I'll take a look.

Cheers

Mike

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Reprocessed to boost vibrance and saturation somewhat ... ( too much ? )

IC 4628 ( Prawn Nebula ) in Scorpius - by Mike O'Day ( https://500px.com/mikeoday )

 

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Well I like it. Don't know really what it should look like, you may well be spot on.

Derek

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11 hours ago, Physopto said:

Well I like it. Don't know really what it should look like, you may well be spot on.

Derek

Thanks Derek

Edited by mike005

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On 24 May 2016 at 02:34, Physopto said:

I like the image a lot, but cannot see any prawns. Tried looking for a while but just cannot see it at all.

Nice though.

Derek

I think I can see a crocodile wearing a pink tutu :)

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