From: Alan Friedman <alan@greatarrow.com>

Date: November 10, 2005 10:30:27 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Camera for guiding

Hi David -

It was good to meet you in Chicago too.

The issues are a little different for Mars, Jupiter and Saturn - but typically I capture between 800 and 1200 frames for streams that will be used in the luminance component of the image (IR, R and G usually) and a little less for the blue - taking care that the length of time needed for the entire capture of streams for one RGB image fits within the timeframe that rotation of the planet will not blur the final composite. There is a significant advantage to be able to use 30fps. Saturn is quite dim currently - I needed to use 15fps with my 10" scope. 

From experience at my location I know that I can use at best about 30% of the frames (7/10 seeing - I get maybe one of these nights a year!) - at worst 10-15%. I can judge the number of usable frames pretty quickly looking at the quality of the video, but on this occasion I did some comparisons between KIS and Astro IIDC so I had a count from the two streams I hand selected using KIS. I adjusted the confidence settings in Astro IIDC to select the appropriate number of frames which worked out between 65 and 70% depending on the stream. Saturn can be done over a longer period because its features are almost all radial in nature - I worked with 8 streams in IR to select about 900 frames used for the luminance in this image. But Saturn does rotate at a similar rate to Jupiter - if you have a night of good seeing and want to hunt for storms or other anomalies in the planets banding you will want to work over a time span of several minutes or any hint of these subtle features will be blurred from rotation.

best,

Alan

What you don't tell us is how many frames you typically capture, where you set the 

confidence level, and how many frames your setting permits Astro IIDC to align and stack. 

I know that that number can vary according to seeing, but some ballpark figures would 

help me and perhaps some others who are trying to learn this art.

Thanks,

David