From: Alan Friedman <alan@greatarrow.com>

Date: October 8, 2005 12:52:47 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] First Astro IIDC shot

Duane -

On Oct 8, 2005, at 2:23 PM, Milton Aupperle wrote:

One thing to keep in mind about using a barlow is that each time you double the magnification, you reduce the light intensity by a factor of 400%.

Are you using the Unibrain color board camera? I have the Fire-I Industrial version but found it quite difficult to use - experimented with it some on Jupiter and Saturn earlier this year, but quickly switched to the monochrome version of the board camera and then to the DMK camera.

The focal ratio expresses the same light throughput regardless of the aperture (but not the same magnification, which is dependent on the focal length of the system). Somewhere in the range of f30-f50 is probably a good target for maximum detail on the planets. Your mileage will vary with the sensitivity of your imaging chip. I routinely image at f45. At this focal ratio I can image in IR, R and G light at 33ms and use a 30fps download rate. Although I can just get by with these settings for B, it will require the gain pushed to max and I usually switch to 66ms and 15fps download rate for this filter. The 4X powermate is very good too - but big, heavy and $$$.

Alan