Camera Settings for Night Photography on Moving Platform

josheiland

1

Camera Settings for Night Photography on Moving Platform

« on: 23 / September / 2015, 18:38:50 »

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Hello,

I'm launching a high-altitude this coming weekend and I want to put a script on my Powershot ELPH 100HS. I'll have the camera on the balloon, and we're launching at night.
Since it's going to be constantly moving, I'm assuming I can't go with a high exposure rate, but I want to optimize the settings to get pictures of the night sky. I was hoping to get a picture every second or two.
Does anybody know what settings I should set, or a good script for this type of photography?

Thanks

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waterwingz

12140

Re: Camera Settings for Night Photography on Moving Platform

« Reply #1 on: 23 / September / 2015, 19:47:24 »

kap_uav.lua provides a lot of flexibility in setting exposure limits and will try for the fastest shutter speed within those limits. It has some other handy features like a delay on start, logging, and (if you use the current beta version) exposure bracketing.

Here's another approach. It also includes a simulation mode so you can "dry run" it.

http://www.francescobonomi.it/CHDK-HAB

This link might help a bit :

http://publiclaboratory.org/wiki/balloon-mapping

and if you are still reading, I posted a few other links here :

http://chdk.setepontos.com/index.php?topic=9740.msg99778#msg99778

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reyalp

14110

Re: Camera Settings for Night Photography on Moving Platform

« Reply #2 on: 23 / September / 2015, 22:55:30 »

Quote from: josheiland on 23 / September / 2015, 18:38:50

I'm launching a high-altitude this coming weekend and I want to put a script on my Powershot ELPH 100HS. I'll have the camera on the balloon, and we're launching at night.
Since it's going to be constantly moving, I'm assuming I can't go with a high exposure rate, but I want to optimize the settings to get pictures of the night sky.

Unless you have a fairly sophisticated stabilized platform, I wouldn't expect night sky images will work very well. My impression is that the payload on most amateur HAB flights swing and rotate quite rapidly. To get more than a few stars, you need exposures of a second or more, which just isn't going to work a moving platform.

You can get an idea of what kind of exposure you need just taking hand held pictures of the night sky, using the highest ISO available. An unstabilized balloon payload will undoubtedly move a lot more than a hand held shot.

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waterwingz

12140

Re: Camera Settings for Night Photography on Moving Platform

« Reply #3 on: 23 / September / 2015, 23:42:26 »

Quote from: reyalp on 23 / September / 2015, 22:55:30

Unless you have a fairly sophisticated stabilized platform, I wouldn't expect night sky images will work very well. My impression is that the payload on most amateur HAB flights swing and rotate quite rapidly. To get more than a few stars, you need exposures of a second or more, which just isn't going to work a moving platform.

While I have no data on this subject, I have looked out the window at 38,000 ft many times while flying comercially and marveled at how bright the night sky is when you leave the haze and pollution far below you. Sure, the stars don't get brighter but they seem less diffuse and filtered. And a HAB project could go much higher than that. So by all means crank up the ISO setting to 3200, leave the camera in P mode and see what happens?

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Ported : A1200 SD940 G10 Powershot N G16

reyalp

14110

Re: Camera Settings for Night Photography on Moving Platform

« Reply #4 on: 24 / September / 2015, 16:41:04 »

Quote from: waterwingz on 23 / September / 2015, 23:42:26

So by all means crank up the ISO setting to 3200, leave the camera in P mode and see what happens?

No harm in trying, but I'd be extremely surprised if to get anything more than squiggly trails. That could be kind of cool on it's own, but I wouldn't expect a nice star field.

For reference, here's a hand held, 1 sec low light mode (binned "ISO 6400") shot from elph130
https://app.box.com/s/j5dy2x75qxwa6agmwzrrhkjxzk3qfyzc

The bright star near the center is Vega. The moon was up and the sun only 10 deg below the horizon, so a dark sky would be a bit better.

This was pointing straight up which is a bit hard to hold steady, but I'd expect something hanging under a balloon to spend most of it's time swinging at multiple degrees per second.

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jmac698

138

Re: Camera Settings for Night Photography on Moving Platform

« Reply #5 on: 07 / October / 2015, 16:57:01 »

I know a solution to this actually. Use the highest ISO you have (don't be afraid if it looks noisy), and short enough shutter speed that there's no star trails, possibly around 1/500. Then use deepskystacker, which can automatically center the images to the same view, then average them out to reduce noise.

http://deepskystacker.free.fr/english/index.html

Automatic registration of a set of pictures
Automatic detection of stars using all the picture area
Preview of registered stars
Sub pixel registration
Automatic derotation

If you're pointing down, you need a different technique.
http://www.autostakkert.com/

This can center and also warp the image to stack (stack means to average several conformed frames to reduce noise). This is important because at far distances, there's some watery effect from air turbulence. I've used this program to clear up images taken on a long zoom from 1km away.

Another way is Hugin
http://hugin.sourceforge.net/

It doesn't denoise like those programs, but you can make a kind of "map" panorama of the ground.

« Last Edit: 07 / October / 2015, 17:03:17 by jmac698 »

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