Re: [ccd-newastro] Re: Exposure time for luminescence images
- Thank you for the explanation - makes sense.
On Feb 11, 2013 11:19 AM, "Stan" <stan_ccd@...> wrote:
> --- Mark Striebeck wrote:
> > What I'm interested in is the relative exposure time
> > (sub, but also overall) of luminance vs. rgb.
> Lum sub-exp time should be determined by its own criteria (e.g. "sky
> limited") and has nothing to do with the sub-exp times of the RGB. Any
> sub-exp L/RGB ratio is happenstance and irrelevant (though once you settle
> into an imaging regime, that ratio will become somewhat constant).
> The L/(RGB) ratio of TOTAL exp times is important but as the prior msg
> stated, the dynamics are not quantitatively well understood and so most
> people experiment to find a ratio that works for them. That ratio can often
> be a result of circumstance; for true resolution it is highly advantageous
> to shot Lum when the seeing is good and fill-in the color data when the
> seeing is otherwise not useful.
> Basically the ratio of total Lum time to total RGB time determines the
> balance of color fidelity vs. image definition/depth. Pure RGB produces the
> highest color fidelity and color-definition but also produces poor depth
> and resolution. Pure Lum (otherwise known as grayscale or B&W) produces the
> greatest depth, contrast and resolution. A strong Lum with under-done
> coloration data can produce washed-out/undifferentiated colors.
[Non-text portions of this message have been removed]
- Hi Mark,
You might want to try my SimCCD and Exposure Planner utilities. They can be used to give a recommended exposure time for that part of the image that is most important to you. For example if you want to get a good signal to noise ratio in the tidal tail of a galaxy, you can select that region and these utilities will tell you how many subs to take. You can find more information about these utilities at
--- In email@example.com, Mark Striebeck <mark.striebeck@...> wrote:
> I found some interesting articles about how to evaluate the different
> exposure times for the RGB images. But I couldn't find anything how to
> determine the exposure time for the luminescence images. Is there a general
> rule or are there good sources to read up on it?
> [Non-text portions of this message have been removed]