White balance in Astrophotography

[bloodhound31]

On the Canon camera's (and most others) there are preset white-balances for daylight, shade, cloud, tungsten, fluro, flash and a custom WB function as well.

Now, while these are pretty easy to grasp, and adjust according to different types of terrestrial lighting, when shooting through a telescope at deep space objects or planets, how relevant are these settings? Is there an optimal WB to choose for all astrophotography or does it change according to the target? I would imagine it would not change.

Does it change if you shoot in RAW or JPEG?

Baz.

[kinetic]

Baz,

I believe you can make a custom WB by simply taking a shot
of white card in pure sunlight.

A custom WB should transfer and work well with deep sky, maybe better
than a camera suggested default WB.

Having said all that, I've never done it myself.

It's been brought up a few times here on IIS.

Just type in custom white balance.

Steve

[bloodhound31]

Thanks Steve, Yes, I suppose it make sense to do this in midday sun as the sun is a star, as are the others.

However, not all stars give off a white/yellow light. We see things on our earth with eyes used to seeing colours under this light as "normal". If you get away from our star by say...1500 light years, what is the true colour and what becomes the new "normal" white balance?

Baz.

[kinetic]

Baz,

not being anywhere near an expert but it comes down to your eyes.
Your eyes have evolved to be sensitive to a certain bandwidth of
light frequencies. Monitors try to display a picture faithfully according to
your eye's characteristic sensitivity curve....or white balance.

Emulsion film...and digital CCDS have also a curve applied to attempt
to display this same curve.

Obviously, if the end receiver is your eyeballs, stuck in front of
a monitor, and any one of the devices used to capture, detect, store,
manipulate and ultimately display it for your eyeball has a different
curve...then it will be a distorted end result.
It makes sense to capture Deep Sky as close as possible to a
generic or custom WB setting...and the easiest way is white card in
sunlight.
I hope this sorta makes sense...

Just one more thing: my ccd camera has a unique sensitivity curve which
may be way off the curve of a typical eyeball.
The easiest way to tune in or calibrate my camera's RGB curves to white
light is to calibrate it on G2V stars....they give off Sun-like light :)
Every high-end astro imager (count me out) has probably done a G2V
calibration of their sensor, or at least, knows the calibration settings.

[bloodhound31]

It does mate, it does.

Thank you Steve.

Baz.

[troypiggo]

If you're not using something like a light pollution filter, I reckon set it to "daylight". If you do use a LP filter, I reckon shoot a neutral graycard in daylight and use that. They're good starting points. But that being said, when you process your images we muck around so much with black points, white point, and the channels that it probably doesn't really make that much difference in the end because it ends up being a processing custom white balance job anyway by default.

[bloodhound31]

Cool bananas Troy. That sounds like good advice. Not sure if it has any bearing on an Orion camera, but certainly for the DSLR.

[White Rabbit]

I use one of my flats as a custom white balance for my 1000d. I use a CLS light polution filter and it certainly helps to use a custom wb.

I'm not so sure about taking a Wb shot in the day time, a white balance shot is supposed to correct for the conditions you are shooting under at the time not 5 hours earlier. But hey, I'm no expert on the subject, and thats a fact.

Sandy

[bmitchell82]

From what i understand if you are shooting in RAW, and i mean proper raw, white balances mean squat.

As troy pointed out you balance your black point, and your white point on the computer once everything has been shot. If it was a big point in anything programs such as maxim would make account for such a setting, but as they do not i do not think you need to worry about it.

The only thing i could say is to shoot the image in proper raw either cannon or something similar, then use a program to de bayer, stack and then process the image to obtain the correct white balance.

If you are obsessed enough to set it in the camera, then i would go for normal sunlight WB, this will reveal the colours as we would generally see it. but there are lots of variables that change this.

Good luck

[dugnsuz]

Image in RAW then white balance on a G2V star...
http://www.astropix.com/HTML/I_ASTROP/CUSTOMWB.HTM

How to find em'...
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3758323/Main/3192162