horsehead wip

[hobbit]

This is 3.8 hours worth of data taken through a Takahashi TOA-150 with a SBIG ST-8300, stacked in maxim dl with darks flats and bias added.

This does not look right to me. Is it a case of not having enough data or have I screwed the processing somewhere?

horsehead wip


Thanks

[MrB (Simon)]

Hi hobbit,

It is definitely processing. With 3.8hours you should have tremendous data to work with.
The image appears to be severely over-stretched(too much contrast) with the black and white points clipped.
I'm not familiar with Maxim, but I know AstroArt can sometimes display an image similar to this after stacking and integrating, requiring me to adjust the histogram.

The following page is about stretching in Maxim:
http://starizona.com/acb/ccd/softwar...basicproc.aspx

But also take a look at the following links about Histograms:
http://www.astropix.com/PFA/SAMPLE3/SAMPLE3.HTM
http://www.lefevre.darkhorizons.org/...orialchap4.htm
http://www.sgastrophotography.com/Sg...hy/Levels.html

[hobbit]

Thanks Simon.
I've gone through that page and came up with this.
horsehead wip
Still doesn't look right.

[Rigel003 (Graeme)]

It's still heavily clipped the black end of the histogram, which means that lots of useful faint data is being rendered as entirely black and completely lost. See the sharp cut off at the left side of the histogram. This needs to be a gentle slope from the base line. You have a terrific combination of gear there so will eventually end up with a great image. Stick at it.

[MrB (Simon)]

That is much improved!
However, as Graeme has said, it's still clipped in the black.
Ideally you would like to see a hump In the histogram like below.
You only want to trim away the 'Unused Dynamic Range' portion at the Black point end.
If you trim the White point end, it may blow-out the highlights(Exagerate the brighter objects)
Your image may appear dark with a histogram like that, so you would then play with the curve.

Check Jerry Lodriguss' tutorial here:
http://www.astropix.com/PFA/SAMPLE3/SAMPLE3.HTM

[hobbit]

third try
horsehead wip