Old 26-10-2008, 03:52 PM
White Rabbit's Avatar
White Rabbit
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Join Date: Feb 2007
Location: Sydney
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My first attempt at astro photography.

This is just one 30sec exsposure, Iso set to 1600 or 800.
My polar alignment is out and the focus isnt great but I'm pretty impressed with how easy it was to get something like this.

I have a question though, well lots of questions but I'll start with this one.

The centre of the neb looks very burt/over exposed yet the surrounding neb looks under exposed. Am I correct in assuming if I turn the ISO down and expose for longer I would be a better result?


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Old 26-10-2008, 04:17 PM
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M42 is tricky, even for the best imagers due to the fact that to get the outside nebula, so to speak one has to expose longer, and then the center gets burnt out.

Many people take a number of exposures at different exposure lengths, and then combine all of these different exposures in PS2 for instance.

One would take say, 10 at 15 seconds to get the core, than some at 1 minute to get the surrounding nebulas, and so on.

They would then combine all of these images, and manipulate them in PS2, or similar software to get the correct levels need to make it all come together.

I am no expert at this but others here will surly advise you further.

However you first attempt is excellent I might add, and you are on the right track.

I do feel that you should keep your ISO at about 400, 800 and 1600 is just to high for this object.

I image at 400 regardless of what I am shooting for, and just lengthen the exposure to suit.

Hope this helps a little bit.

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Old 26-10-2008, 04:19 PM
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Octane (Humayun)
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White Rabbit,

Good first attempt.

With this particular nebula, if you expose for longer, no matter what ISO you use, you will burn out the core; it is just too bright.

I've seen two fixes to this issue:

1. don't bother; just leave it as it is;
2. take shorter exposures of the core and super-impose over the top of the correctly exposed nebula using masking in applications like Photoshop.

Keep going -- it's a very steep learning curve. Taking images is half of the battle (and this is assuming that all other variables such as weather and functioning equipment is swell), the rest of it is in post-processing.

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