From: Alan Friedman <alan@greatarrow.com>

Date: March 26, 2008 1:40:55 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] dancing with the moons...


Hi Jim,


It's a lazy susan full of trade-offs. Using the DMK camera at f30 in full white light, there is enough light to shoot at 33ms and 30 fps. But with the blue light included, the seeing always suffers badly. I (almost) always have better results using RGB filters to attenuate the turbulence for luminosity data. The light loss requires me to increase the shutter to 66ms (15fps) with a high gain setting or 133ms for a better signal but softer image. I find the differences between these two settings to be pretty much a wash. At one time it was very difficult for Astro IIDC to work with the noisy images (gain setting greater than 950) - but with the gaussian blur option the selection and alignment is much more accurate. 


One can, of course, drop down in focal length to increase the brightness and combat the seeing - but at a cost of resolution potential. I find my 10" at f30 is just about right for our location.


But I'm stilling hoping for that free lunch!


Alan



On Mar 26, 2008, at 1:37 PM, Jim Chung wrote:

Hi Alan,

Just read your response to Mark and I'm surprised you imaged with the gains set
to near maximum. Is that the preferred way to go and risk introducing noise
rather than increase exposure time?

Jim