What is the best script for Time-Lapse Astropphotography??? - Script Writing - CHDK Forum
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What is the best script for Time-Lapse Astropphotography???

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Offline apfrsscf

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What is the best script for Time-Lapse Astropphotography???
« on: 19 / June / 2012, 17:58:05 »
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Greetings CHDK
What is the best script to use for Time-Lapse Astrophotography???
I realize that this is a loaded question, so here are some parameters:
I am running v1.01b on a sx230.
I got acceptable results with the default Intervalometer.lua that was already installed, but it will not adjust exposure for sunsets/dusk, etc. I tried Sunsetf16.lua, but I could not get it to run.
I am new to CHDK and I am having trouble finding explicit directions of exactly how to install scripts and their associated files. I am also fumbling with how and what to adjust settings to. It looks like the Basic language is understandable (I have experience with Excel Macros), so I may eventually write my own scripts.

I have access to VERY dark skies. I want full detail in the milky way. That means very long exposures at very high ISO (60 second or more at ISO5000). I hope to do Fading Star Trails, but I am still learning.

Clear Skies
apfrsscfr
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Offline outslider

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Re: What is the best script for Time-Lapse Astropphotography???
« Reply #1 on: 20 / June / 2012, 01:07:00 »
You can try this:

http://chdk.setepontos.com/index.php?topic=7757.0

This script will calculate exposures. Written especially for sunset/sunrise but its quite universal.

Examples:

sunrise
output.avi

day-noght-day (little bit boring and poor quality)
Time-lapse day-night-day
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Compile error: poor Yorick
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Offline apfrsscf

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Re: What is the best script for Time-Lapse Astropphotography???
« Reply #2 on: 20 / June / 2012, 15:08:43 »
Thank you outslider. I'll give it a try. Please stand by (it could take a while) for results/comments/questions.
Clear Skies
apfrsscf

p.s. I tried to attach a video, but it is too big. Guess I have more work to do first...
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Offline outslider

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Re: What is the best script for Time-Lapse Astropphotography???
« Reply #3 on: 20 / June / 2012, 15:56:41 »
Upload the video on YT and then just paste a link in your post here. It'll be shown like in my post above.
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Offline apfrsscf

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Re: What is the best script for Time-Lapse Astropphotography???
« Reply #4 on: 30 / June / 2012, 19:04:31 »
Well I had some success and some failure with this script (not the script's fault).
I went out to a dark sky site and started recording around sunset. The 1G memory card filled up just as the stars started becoming visible. Of the exposures that I gathered, the relative brightness is extremely consistent. The only difference is that that as the series progresses, you can see stars starting to become visible.
Since then I have been experimenting to try to determine what the best ISO to use. Obviously the higher the ISO to more noise. I will not be able to fully determine that until I can get back out to dark sky site again. It is now raining...

I am attaching a frame with Leo becoming visible.
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Offline outslider

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Re: What is the best script for Time-Lapse Astropphotography???
« Reply #5 on: 30 / June / 2012, 19:34:06 »
Nice :) Thanks for sharing. I hope you'll get good results. Note, that when you change ISO then the script will adjust the shutter time to get the same exposure, so you'll end up with almost the same image. Two differences will be:

- less/more noise (higher ISO - higher noise, however, lower ISO -> longer exposure -> higher noise...)
- different shutter time might cause your stars will be not points but short lines.

If you want to change the brightness then you have to use correction parameters of the script.
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Offline apfrsscf

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Re: What is the best script for Time-Lapse Astropphotography???
« Reply #6 on: 01 / July / 2012, 11:42:49 »
Question: How exactly do I change the correction parameters of the script to adjust the brightness?

Also I did another test last night. After 103 exposures (a little over 1.5 hours) the camera used up all the battery power (it was 89% when I started) and shut down. What can I do to improve this? (An A/C adapter is not an option when I go up into the mountains.)
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Offline waterwingz

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Re: What is the best script for Time-Lapse Astropphotography???
« Reply #7 on: 01 / July / 2012, 11:56:41 »
Quote from: apfrsscf on 01 / July / 2012, 11:42:49
Question: How exactly do I change the correction parameters of the script to adjust the brightness?

Also I did another test last night. After 103 exposures (a little over 1.5 hours) the camera used up all the battery power (it was 89% when I started) and shut down. What can I do to improve this? (An A/C adapter is not an option when I go up into the mountains.)
Well, first off,  89% is kind of an arbitrary measurement - it might have actually been almost half exhausted.  So obviously, starting with a fully charge battery is always a good idea.

People have done some fun work making scripts more efficient - even to the point of switching to "playback" mode automatically between shots because somebody did the measurements and found out that "playback" uses somewhat less power.    However,  we are talking about maybe a 25% improvement (my guess) with a really good script.   YMMV.

So your other choice is a remote battery pack.   That becomes a function of how much weight you want to carry vs how long you want the camera to run.

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Offline apfrsscf

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Re: What is the best script for Time-Lapse Astropphotography???
« Reply #8 on: 01 / July / 2012, 12:51:14 »
I now have two batteries. When I go to a remote site I will make sure that they are both fully charged.

Just out of curiosity, does the CMOS chip draw most of the power? (I am using a sx230) Is there a way to shut it off (without shutting the whole camera down)? I notice that the CMOS chip gets quite warm which also increases noise. Wouldn't giving the CMOS chip a rest save power and reduce thermal noise?

Also is there a way to shut off the LCD screen? It actually puts out a lot of light. I had thoughts that if we could tone that down that we could save some power as well as not ruin everybody's night vision.

Correct me if I am wrong: a digital camera is essentially a computer in that it has input devices (including the CMOS chip), some kind of CPU, memory storage, and output devices (including the rear LCD screen).
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Offline waterwingz

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Re: What is the best script for Time-Lapse Astropphotography???
« Reply #9 on: 01 / July / 2012, 12:57:55 »
Quote from: apfrsscf on 01 / July / 2012, 12:51:14
Just out of curiosity, does the CMOS chip draw most of the power? (I am using a sx230)
I would only be guessing if I tried to anwer that.

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Is there a way to shut it off (without shutting the whole camera down)? 
Not that I know of.

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Also is there a way to shut off the LCD screen? It actually puts out a lot of light. I had thoughts that if we could tone that down that we could save some power as well as not ruin everybody's night vision.
Typically,  most intervalometer scripts issue a set_backlight command after each shot to turn off the backlight.
http://chdk.wikia.com/wiki/Script_commands#set_backlight.28.29
It doesn't actually save a lot of power but as you said, it gets rid of the distraction.   You can also stick an external video connector (or wedge in a toothpick apparently) to actually turn off the display and backlight - which saves a little more power.

Search the forum and you will find a lot of threads talking about this.

http://chdk.setepontos.com/index.php?topic=2644.msg24572#msg24572
http://chdk.setepontos.com/index.php?topic=6615.msg71495#msg71495
http://chdk.setepontos.com/index.php?topic=6207.0
http://chdk.setepontos.com/index.php?topic=5797.0
http://chdk.setepontos.com/index.php?topic=2075.msg19129#msg19129

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orrect me if I am wrong: a digital camera is essentially a computer in that it has input devices (including the CMOS chip), some kind of CPU, memory storage, and output devices (including the rear LCD screen).
Yes - although most of them have more than one CPU - there is a generic ARM processor and a specialize DSP in there.
« Last Edit: 01 / July / 2012, 13:01:08 by waterwingz »
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