IC410 - more data

[Robd]

I posted a version of this a few weeks ago, at the time 6 x 600s.

Since then I have got another two hours worth to add to the first hour.

I have also built a light box and added some flat frames to the stack which has got rid of few bunnies.

6 x 600s iso 800

12 x 600s iso 400

Stacked in DSS

Dynamic background extraction in PixInsight - not sure that I have this right just yet, I only came across it following a post in here ( TJ I think )

Tweaked every which way in Photoshop - levels and curves, Noel's noise reduction and local contrast enhancement

The light pollution was dire particularly on the second outing. I have tried removing it but that also removes most of the nebulosity.

Pentax K10D

Skywatcher 150 f5

Baader contrast booster

Guided with PHD using 120mm refractor.

Ok this is first image post so hope that it works

Comments critique etc. welcome as usual.

Rob

[Robd]

Had another play.

Re-re3ad the PixInsight instructions and realised that I had subbed the background instead of dividing

Managed to get rid of some more of the light pollution so picture seems better balanced too me.

Rob

[Tim]

Some nice detail starting to come through there Rob. It's not an easy target I found.

Have you tried using star masks? With them you can enhance the nebulous parts without affecting the way the stars look, and it helps keep them nice and tight.

I haven't actually read the instructions for pixinsight, but the technique I use seems to work ok. But on an image with so many stars, would it struggle to get a decent background sample?

I usually do this, please let me know if the instructions say to do different!!

1) Select DBE tool and click on image to bring the toolbox up. Under the global tab, I set the auto intervals to 15 or 20, and the image size to 1:1 or 1:2, depending how accurately the gradients need to be dealt with. Click the top Generate button.

2) I then remove any point which is positioned over a feature, star, nebulosity etc, and if the background has especially bad features, then put lots of extra points in and around the area.

3) Click the bottom generate button, which brings up a new image, the background of your image without the stars. Close the DBE tool.

4) I then click Process > General > Pixelmath >New, with SUB as the operator, and the new background image as the operand.

5) Click > apply and then select the main image as the one to subtract the background from.

6) save the image that pops out, with the gradients pretty much gone.

Is that not right then ? ? ?

Incidentally, I have used the full paid version, and the background extraction on that is better still.

Thanks

[Robd]

TJ,

Sounds about right. The only difference is that the instructions quote "

A CCD image could now be flattened by straight division with the generated background model. This works because CCD sensors are linear.

But we are dealing with a film image here, so the relation between numerical pixel values and actual brightness of represented celestial objects is strongly nonlinear." etc.

So for a ccd image divide the image by the background whereas the instructions go on to describe the process for a scanned film image where sub is used.

Rob

[Robd]

TJ,

Sorry only answered half the questions.

I have had a play with star masks - first attempt, and of course struggled. I ended up with a black hole round each star. I suspect I was doing something wrong. Things that spring to mind are:-

Taking star mask to early/late.

stretching image too far

Insufficient/too much of something else.

Yet another imaging mine field to get round.

Rob

[bazza]

Hi Rob,

Obviously the second image is much better - lots of nebulosity starting to come through.

You do seem to have suffered from light pollution somewhat.

I wonder what it would be like without the Baader contrast booster?

I'd have thought this would stop a fair bit of signal getting to the camera?

Maybe more than a simple CLS filter?

Just ideas really - I know there's no substitute for plain old exposure time.

Barry.

[Robd]

Hi Barry,

You could be right. The Baader CB might be cutting too much. Having said that the conditions were not good especially for the second lot of 1hrs. I think that there was a lot of moisture in the air which really reflected the light a lot.

I had thought of a CLS filter but funds so not allow at the moment. Perhaps after our daughters wedding ready for next winter. I can always dream.

Rob