MOVED: How to avoid noise?

[Astrosurf]

Hi all, I've followed Astronomyshed's tutorial about Levels and Curves to have another go at my Orion nebula, but even though I avoided posturization and other problems, to bring out as much detail as possible I got more and more noise. I've had to blur some areas to reduce it! I only managed to snap 6 pics and one of them was duff so I didn't have that many to get a lot of data. I stacked the RAW images. The attached is a reduced JPEG of the TIFF.

What would you have done?

Alexxx

[Tron]

Ear defenders? Cuts out most noise for me

[Shibby]

There is no substitute for # of subs!

However, to minimise the noise in processing I think the most important thing is to be very iterative. Only make *very* small adjustments to the curves on each iteration.

Also, you can process twice, one carefully for the brighter detail, and one more aggressively for the fainter stuff (using noise reduction), then layer the 2 together.

[Dann]

Good advise Lewis, I had never thought of processing the same data twice and blending them together.

[Astrosurf]

Ear defenders? Cuts out most noise for me

[Astrosurf]

There is no substitute for # of subs!

However, to minimise the noise in processing I think the most important thing is to be very iterative. Only make *very* small adjustments to the curves on each iteration.

Also, you can process twice, one carefully for the brighter detail, and one more aggressively for the fainter stuff (using noise reduction), then layer the 2 together.

Is there an easy way for you to tell me how to do that? Or maybe you can find me a link or a suggestion on what terms I can Google? I have PS 7.

Many thanks guys!

[martin_h]

More sube will cut the noise, you had 6, doublke or treble the sub count, that will make a difference.

Two images into one - Compositing 2 Different Exposures via Layer Masks

[Astrosurf]

Thanks Martin. I'll have a perusal tonight.

[RobH]

Hi Alexx.....the only way to reduce noise is to take lots and lots of subs....the result you've got is great, especially as you've only got 6 subs, but, as you found, you rapidly run into noise issues in the faint areas......you should be looking at a minimum of 30 subs, and more if you can get them.

Have a look on my website under 'primers and tutorials'....there's a section on signal to noise etc there.

Admittedly, I'm somewhat obsessive, but, for example, I'm currently working on an image of M31 which has over 60 x 15 minute subs. The reason I do so many is simply to reduce any noise to an absolute minimum so I can stretch the faint regions and still keep them smooth.

Cheers

Rob

[Astrosurf]

Hi Alexx.....the only way to reduce noise is to take lots and lots of subs....the result you've got is great, especially as you've only got 6 subs, but, as you found, you rapidly run into noise issues in the faint areas......you should be looking at a minimum of 30 subs, and more if you can get them.

Have a look on my website under 'primers and tutorials'....there's a section on signal to noise etc there.

Admittedly, I'm somewhat obsessive, but, for example, I'm currently working on an image of M31 which has over 60 x 15 minute subs. The reason I do so many is simply to reduce any noise to an absolute minimum so I can stretch the faint regions and still keep them smooth.

Cheers

Rob

Thanks Rob, I'll check your tutorial. I too am very fussy, but I'll need to autoguide before I can get subs even remotely that long!

Cheers,

Alexxx

[RobH]

Thanks Rob, I'll check your tutorial. I too am very fussy, but I'll need to autoguide before I can get subs even remotely that long!

Cheers,

Alexxx

If you can't get long subs Alexx, get loads of short ones....if you can go to 120s subs for example, it'll only take you 2 hours to get 120 of them, and that will really knock your noise levels down.

Cheers

Rob

[Tim]

I'll put the thread in the Help section..

Cheers