From: Alan Friedman <alan@greatarrow.com>

Date: November 13, 2007 10:32:33 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Barlows and Mars

Hi Duane -

14 meter focal length? I didn't do the math, but I think you may be oversampling without benefit. I think oversampling in certain conditions does have the potential to record high contrast detail that might be missed at lower magnification - but it takes excellent seeing and a contrasty subject to yield any advantage. Otherwise you wind up with needlessly noisy data that defies accurate alignment when stacking. I've used my 10" mak at 11 meters, but I think my results at 7.5 meters are as good and perhaps better. Just my .02 - you might try it both ways and see if you find improvement in the image at high magnification.

steady skies,

Alan

On Nov 13, 2007, at 12:04 PM, Duane wrote:

Last night I tried my 5x Powermate for the first time in ages and found that on my
Celestron 11" f/10 that I could image much the same as I could with my Celestron 2x
barlow on my 8" LX200 f/10.

If I want more speed, I still resort to the smaller 2x and I am considering getting a 3x
barlow.

But I like the size I'm getting with the 5x. My images were pretty fuzzy after shooting, but
with the extra size I could sharpen and reduce the size and still end up with a pretty
decent image.

http://homepage.mac.com/deal/share/mars_11_13_07.jpg

Duane

.