From: "Milton Aupperle" <milton@outcastsoft.com>

Date: April 22, 2008 10:15:46 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: Astro IIDC dark frames  and "Use Sharpness for Capture" issues


--- In Astro_IIDC@yahoogroups.com, "doodlebun" <gbleser@...> wrote:


In the manual Milton states that Dark frame subtraction is really only 

appropriate for 1 sec exposures or longer. Does this mean that I should 

just forget about making dark frame movies for Planetary imaging? 


Yes, your not really gaining anything with dark frames for those

camera. And Dark frames are mainly for Deep Space Objects.


I suppose I should have the box checked for automatic hot and cold pixel 

subtraction, assuming my MacBook is fast enough (you mention the CPU 

load).


Unless your seeing hot (bright stuck) and cold (dark stuck) pixels I

wouldn't use it as it uses up a lot of CPU cycles. Agian, it's

primarily for DSO objects Or if your camera has a lot of defective

pixels which becomes really noticeable as you increase the gains.



Also I notice that if when capturing images of Saturn I don't seem to 

be able to "Use Sharpness for Capture" option. The movie starts but no 

frames are captured, implying that nothing "is good enough" for the 

software! I am using the default settings. Perhaps you can advise.


What you missed is that you need to enable what it is accepting or

rejecting as far as frames go by clicking on the "Sharpness:" pop up

menu and select the "Pixel Edge On" menu item. (see page 64 and 65 of

of the manual). If that's check marked, then is will indicate what

frames it is rejecting as not good enough by displaying the word

"REJECTED" in the video preview window.


Also you can't adjust exposure, brightness or color gains after you

have estimated your "sharpest" frames. As that will throw all the

frames into the rejected pile. You might want to increase the number

of frame sits averaging too, which again depends on how turbulent your

skies are.


And it really won't work well if you have lots of turbulence or if you

have very high brightness / gains set. It primarily was designed for

higher contrast objects like the moon or a limb or other features.


HTH..


Milton Aupperle