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Star trails

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Offline dom-a

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Star trails
« on: 24 / January / 2009, 18:21:08 »
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This is a stack of 13 images with 64 second exposures. It would have been more but I was cold, and I wanted my dinner.
I used a PowerShot A570IS
CHDK helped with.
1, shooting RAW.
2, turning off noise reduction.
3, 64 seconds exposures.
4, interval meter.
5, ISO override.

Re: Star trails
« Reply #1 on: 26 / January / 2009, 06:47:04 »
It's nice! I tried a similar thing some weeks ago but I failed for some reason.

Can you describe how you did it? Both the CHDK settings and the post processing on your computer?

Thanks in advance

//Ola

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Offline dom-a

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Re: Star trails
« Reply #2 on: 26 / January / 2009, 08:28:15 »


here is another one I did last night, in my back garden. 60 frames at 64 seconds.

Camera settings.
Exposure time 64 seconds.
Aperture, f2.6.
ISO, 200.
Review, off (important)
Noise reduction, off (important)

Interval meter settings.
Delay 1st shot, 5 seconds.
Number of Shots, 60 (or any number you want).
Interval, 0.

Set your camera up on a good and stable tripod. You don't want any camera movement.
The settings above are setup to keep the shutter open as long as possible during the shoot.
Youe need to take a dark frame during the shoot. I normally do it at the beginning, but you must let your camera warm up for about 10 minutes before your take it.
Now your camera is set up, point were you want and set if off. Retire to some were warm.

Post processing.
I shoot in raw, because I can and it makes doing the dark frame subtraction easier.
Software I use:
UFRaw.
The GIMP.

1. Do the dark frame subtraction, the more frames your taken the longer this is going to take.
2. Using The GIMP (or any half decent images editor with layers) open the first frame.
3. Click and drag the next frame on to the first. this should add another layer to your first frame.
4. In layer mode chose 'lighten only'.
5. Repeat steps 3 and 4 till you finish. Or you get board.

Tip. As you add more and more layers the computer has to do more work. After about 8 layer go to flatten image, this merges all the layers together and you can carry on adding more layers.

If you have any more questions I'll try and answer them.

Re: Star trails
« Reply #3 on: 26 / January / 2009, 09:19:12 »
I think I missed the following:
 * Camera setting: Review, off (important)
 * Camera setting: Noise reduction, off (important)
 * 1. Do the dark frame subtraction, the more frames your taken the longer this is going to take.

Last time I tried I shot in JPEG and I couldn't find a way to do the dark frame subtraction. I'll try in RAW and do it with UFRaw.

Thanks for the help!


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Offline barret

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Re: Star trails
« Reply #4 on: 26 / January / 2009, 09:38:46 »
why not use startrails?
http://www.startrails.de/html/software.html
it does the same, automagically :)

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Offline dom-a

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Re: Star trails
« Reply #5 on: 26 / January / 2009, 09:43:44 »
You can do the dark frame with The GIMP. By using the layer mode and 'subtract'.

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Offline barret

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Re: Star trails
« Reply #6 on: 26 / January / 2009, 09:48:55 »
yes, i know GIMP is nice, I'm using it too.
but still, you can do dark frame subtraction in startrails too :)
why not use tools created for specific purpose? i mean, free tools.

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Offline dom-a

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Re: Star trails
« Reply #7 on: 26 / January / 2009, 10:05:32 »
yes, i know GIMP is nice, I'm using it too.
but still, you can do dark frame subtraction in startrails too :)
why not use tools created for specific purpose? i mean, free tools.

Last time I checked, which was about 1 minute ago. Startrails isn't available for Unix OS'is.

If your running Window by all means fell free to use startrails.


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Offline barret

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Re: Star trails
« Reply #8 on: 26 / January / 2009, 10:21:40 »
true, i forgot to mention that startrails is available only for windows platforms.
as for *nix platforms: is there any way to automate this process? i know GIMP can batch process images...

Re: Star trails
« Reply #9 on: 26 / January / 2009, 12:23:04 »
as for *nix platforms: is there any way to automate this process? i know GIMP can batch process images...

You can use ImageMagick

Review, off (important)
Noise reduction, off (important)

Are you disabling these settings to reduce the delay between frame?
« Last Edit: 26 / January / 2009, 12:26:01 by cedricb »

 

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