From: "Duane" <macastronomer@mac.com>
Date: November 14, 2007 1:43:21 PM MST
To: Astro_IIDC@yahoogroups.com
Subject: Re: Barlows and Mars
I agree that it's a bit much. But the seeing wasn't all that great but I was amazed at what I
could do by sharpening (various pixel spreads) and then downsizing the image. It really
did look better than images captured with a 2x sharpened and left native size.
I think it has to do with the fact that I can pull more like shades together. If I sharpen to
the extent on either image, it becomes a mess of pixels. The larger image can be
downsized and photoshop causes those pixels to disappear between the pixels of the new
resolution.
Maybe I was up too late or maybe I'm just nuts, but I can't wait to try this when the sky
gives me some stability.
In any case, I just bought a 3x TV barlow for a better focal ratio than I was capable of
before. The 2x I was using was a mediocre Celestron with some apparent dust specs that
I've never been able to clean. I was amazed I was able to get any kind of image with the 5x
and compared to the original, I'm even more amazed.
Duane
--- In Astro_IIDC@yahoogroups.com, Alan Friedman <alan@...> wrote:
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
.