Imaging the Orion Nebula (Advice Please)

[OzDave]

Hi,

A while back I took some 30s subs of the Orion Nebula, which turned out ok-ish as subs go for a total beginner, but basically unusable for stacking due to problems with my setup that I'm gradually ironing out.

However, recently I was reading some articles about imaging this particular target that suggested that the core of the DSO is very bright and that too long an exposure will "blow the core" in the subs so that you end up with a white patch in the middle but more detail in the fringe areas on the nebula. Looking at my old subs, I can see how this would happen fairly easily.

The article said that a more normal way to image this type of DSO is to capture subs with a variety of different exposure times. Longer exposures to capture more details in the faint outer parts of the nebula and shorter exposures to get the detail and stars in the bright inner core.

What I don't understand is what to do with the subs once you get them? Say you stack all the subs of the same exposure length and end up with one master for each length of exposure. Then what? How do remove the blown out core from the longer exposures and replace that with the more detailed core from the shorter exposures?

I am guessing it's not a stacking operation that is needed here, but more of a cut/paste layering job in Photoshop or something?

Or have I got the wrong idea completely?

Thanks,

David

[MikeD]

Hi,

I am guessing it's not a stacking operation that is needed here, but more of a cut/paste layering job in Photoshop or something?

Or have I got the wrong idea completely?

Thanks,

David

Thats about it. click me

Mike.

[Daz1969]

Excellent! I wondered how you did that:icon_salut:

Cheers for sharing

Daz

[michael.h.f.wilkinson]

There are actually better techniques (closely related to stacking) which create a high dynamic range image out of the stack, by combining exposure-time information and detecting saturation (clipping) of each pixel. Once the high dynamic range image is created, unsharp masking can be used to reduce the dynamic range to something useful for printing or viewing on a screen.

I know these tools from the image processing classes I teach, but do not know whether any tools exist to do this easily.

Cheers

Michael

[Psychobilly]

In DSS you can use Entropy weighted stacking...you really need lots of subs to control the noise though when you use it..

Peter...