PDA

View Full Version here: : G2V star white balance


troypiggo
07-12-2010, 11:58 AM
(not sure where to post this)

Done some reading and (think I) understand the why and how of using G2V stars for white balancing images. I filtered out of the Hipparcos Stellar Catalogue stars with G2V designation and now have a list of over 600 stars in AstroPlanner that I can use. Trouble is, they're often not in the field of view of what we're shooting.

Wondering a couple of things.

Are there other stars that are "close enough" that you could use as well to increase the coverage, maybe higher chance of getting some in the field of view? eg there's some 1200 G2 stars, or maybe just any old G type star is near enough?

If not, how do you handle it? I guess you'd shoot a G2V star separately to your intended target, and just match the white balance of the 2 different shots? Do you do this every time you shoot, or just once with that equipment?

Am I overthinking this? Should I even bother?

Why are we here? Who am I? :)

rally
07-12-2010, 12:20 PM
Troy,

Could be the selection in the database you are using.
What is your focal length and FOV - is it that narrow ?

Here is a link to one commonly used with TheSky6

http://www.astrodon.com/custom/_2e2a/content/files/G2V.zip

CCDWare's AutoPilot also has a one click G2V calibration option - with extinction correction - works best with TheSky6 though !
http://www.ccdware.com/products/ccdap4/whatsnew.cfm

Cheers

Rally

troypiggo
07-12-2010, 12:33 PM
FL 600mm (ED80) and 40D DSLR - FoV around 2.4deg x 1.6deg. Also have 10" newtonian 1200mm FL 1.4deg x 48sec FoV approx I think.

I don't have TheSky6. Could be right on the catalogue. I used that Hipparcos one because it has spectra data and I'd read some websites that quoted it. Not sure if there's a better one.

telemarker
07-12-2010, 12:42 PM
Although I haven't used it, you could try this (http://bf-astro.com/software.htm).

Geoff45
09-12-2010, 11:52 AM
This is excalibrator, which I use all the time. It works pretty well for areas covered by the Sloane digital sky survey (ie accurate data) and is patchier for the remaining areas (covered by NOMAD). Usually works pretty well though and is easy to use once you go carefully through the very well written manual.
Certainly worth having in your armoury.

telemarker
09-12-2010, 04:01 PM
Handy to know. Mainly doing Narrowband ATM but will eventually need to look at this. Also, Rogelio Bernal Andreo has some tools here (http://blog.deepskycolors.com/tools.html). As a side note I'm looking forward to his presentation at the first Oz imaging conference - his website is packed full of amazing images.