DBE

[Harry page]

Hi Learned people

I am having trouble using DBE with faint nebula!
I find that it over flattening and loosing some faint detail  ( I can see this in photoshop, yes I know wash my mouth out with soap and water)
I have tried many settings, but as usual I am probably doing it wrong?
Can someone point me in the right direction please.
I have read the tutorials  many times and have no problem when there is reasonable signal, but seems a shame to loose some info

Regards Harry

P.s  Love the soft ware and keep up the good work.

[Juan Conejero]

Hello Harry,

I am having trouble using DBE with faint nebula!

Indeed this isn't an easy task. To help you, I would need to take a look at the image. Then I'd try my hand at it with DBE. Could you upload the image (not a JPEG of course, but the actual image)? If you want, you can use the anonymous ftp account on our server.

[Simon Hicks]

Hi Harry,

I've found the following is a good way to use DBE and not take away faint nebulosity. Firstly, use DBE to generate a modelled background. Spend plenty of time playing with the parameters to get a good 'looking' background, i.e. one that has the same shape and colour as the background.

But you don't want to subtract the whole of this background....you want to subtract say 50% or maybe 80% of it. So put something like Image1-(0.8*Background) into PixelMath. Or maybe even subtracting a small value from Background would do the same thing but better.

In this way you get a flatter image, but you have not taken the background down to zero....so your faint nebulosity is still there in the dark depths of the data.

Cheers
             Simon

[Harry page]

Hi Juan


I will upload a file to your FTP server tonight for your consideration

Regards Harry

[Harry page]

Hi Simon

Thanks for the idea, had never thought of doing that !
Will have a go and see what happens.


Regards Harry

[Simon Hicks]

Hi Harry,

Actually, thinking about it, subtracting a small pedastal from the Background is maybe better than multiplying it by 0.8.....multiplying it will change the shape slightly....a subtraction will just lower all values by the same amount preserving the shape.....maybe not enough to worry about, but it will have an effect.

I'm not sure how to determine how much to subtract. Maybe you look at the lowest pixel values in the modelled background and then subtract 20% of that from the whole background image......then subtract that from your original image.

Maybe Juan can help? He usually has a far simpler / better way of doing these things.  :lol:

Cheers
              Simon

[Juan Conejero]

A quick try with Harry's nice M42 image, from the tutorial that I'm working on:

http://forum-images.pixinsight.com/legacy/M42-ian-page/test1.jpg

This has the following processes applied:

- DBE
- HistogramTransformation
- HDRWaveletTransform
- ACDNR applied in two stages, for small-scale and large-scale noise reduction
- HistogramTransformation
- CurvesTransformation, only a saturation curve
- Resample to approx. 1800x1200

I am writing the script for a video tutorial right now. I hope to have it ready tomorrow, with the unvaluable help of Alex of course

Thanks to Harry Page for allowing me to use his image to write this tutorial.

[Harry page]

Hi Juan

Look forward to you showing the error of my ways to me!

Regards Harry

[Juan Conejero]

Hi Harry, Simon, and everybody,

I've just uploaded a first part of the tutorial with Harry's nice M42:

http://pixinsight.com/forum/viewtopic.php?p=4713

Hope you'll like it; more to come.

Thanks Harry!

[Harry page]

Hi Juan

Thanks for the video!
Sure this will assist in mine and others work.

Will see how good I can get

Regards Harry

[Harry page]

Hi Juan

I have studied your tutorial in detail and has been of great assistance.
I did not realise that you could manage with so few samples in the outer area and was over doing it !
For future referance what would you do if you had no free background at all ?


Regards Harry


PS  looking forward to part 2

[h0ughy]

Hi Harry, Simon, and everybody,

I've just uploaded a first part of the tutorial with Harry's nice M42:

http://pixinsight.com/forum/viewtopic.php?p=4713

Hope you'll like it; more to come.

Thanks Harry!

i just tried  this link and it doesnt seem to work?  any other requirements apart from clicking on it?

[Nocturnal]

The forum was updated yesterday and now old links are broken. You can find the video tutorials linked from the pixinsight home page or here: http://pixinsight.com/videos/index.html

[h0ughy]

The forum was updated yesterday and now old links are broken. You can find the video tutorials linked from the pixinsight home page or here: http://pixinsight.com/videos/index.html

thanks