From: Alan Friedman <alan@greatarrow.com>

Date: September 27, 2010 8:49:37 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Jupiter Image

Hi Tim,

What's the amplification of the tele-extender that you're using? I use a 2x barlow+filter wheel+camera on my f14.6 mak and the image scale works fine in average seeing. At f7 you shouldn't have any problem with image scale using a 2x or 3x barlow in this configuration.

The fine image that Alberto posted was taken in Australia, clearly in very fine seeing conditions. When the seeing is sublime, you could get a good image with a Kodak instamatic. I am not a fan of color cameras. They are so much less versatile than monochrome cameras. But perhaps the biggest loss is the ability to reap the stability benefits of imaging in narrow slices of the visible spectrum. Being able to remove the turbulent blue data from luminance is a big advantage in average seeing conditions. If one were to image all the time, you run the chance of happening upon a few moments of steady seeing when a color camera can shine. But those who image all the time invariably choose a monochrome camera. The color camera is used mostly as a convenience by those who image the planets infrequently, and hence the chances for capturing a fine image tend to be slim from all but the very best locations.

my .02,

Alan

On Sep 27, 2010, at 10:03 AM, doobisary wrote:

Hi Milton:

I thought I'd replied yesterday but my internet connection was flaky and it musta notta gotten in!

Anyway, I had posted my thoughts about color versus mono cameras. I've only used my Scorpion for RGB imaging a couple of times now, as I only fairly recently purchased an Orion manual filter wheel.

Problem I have with LRGB imaging is that my old Newts don't have enough backfocus for all the "stuff" in the camera assembly. My 8" f/7 Cave doesn't even have enough backfocus to reach focus with the Scorpion by itself at prime focus. It does reach focus with a barlow in place, though. But to use the filter wheel, I have to put the wheel between the barlow and the camera, which gives me too large an image scale for the seeing.

I much prefer color camera imaging of planets, and am excited to see your results with the Chameleon and the exhad ccd. I've been wondering whether to buy one of those versus a mono or color flea3. Your results have me thinking I might go for a color Chameleon first, and then try the mono flea3 when I can afford it.

-Tim.

--- In Astro_IIDC@yahoogroups.com, Milton Aupperle <milton@...> wrote:
>
>
> On 26-Sep-10, at 5:01 AM, albe albo wrote:
>
> >
> >
> > Hello Milton,
> > nice for a color camera.
> > I am not able to get good result with my DFK, i don't know why.
> > The details are always so messed up while with the DMK and the
> > filters it seems to go better.
>
> Yes, that's always been the case and has been discussed on this list
> many times. Bayer cameras are lower resolution (by about 50%) over
> Mono cameras. You mix adjacent color pixels together with Bayer
> filters to create the images.
>
> > Perhaps it is due to the possibility to process 3 or 4 different
> > channels so the averaged result is better.
>
> Yes.
>
> However you also need good seeing for all 3 / 4 LRGB imaging sessions,
> so under my normally mediocre skies (>4+ arc seconds of motion) you
> get worse images that way. Fine details never show up anyhow except
> for maybe 1 or 2 nights a year.
>
> Also with Jupiter's fast rotation, you have to shoot very quickly (or
> only a few frames) or you get rotational offsets between images.
>
> > 30° above the horizon?
>
> It was 20° when I started taking images and Jupiter only gets to 35°
> above the horizon here maximum, so I'm shooting though nearly 2x as
> much Air turbulence as other people.
>
> > Wow...i didn't remember you live so much at north.
>
> Yes I'm at 50.5° N latitude.
>
> > Only a question : why did you leave the image so uncorrected
> > regarding the white balance?
> > In my opinion it is pretty cyanotic.
>
> I color balanced using the moon to "gray", when it was about 15° above
> the horizon. Which means it was dominantly red getting though
> atmosphere at that Altitude. By the time Jupiter got to 29°, the Blue
> and Green channels brightness increased.
>
> > I played with an automatic white balance (no other corrections) and
> > perhaps the result is overcorrected but more similar to the visible
> > Jupiter.
> >
> > http://dl.dropbox.com/u/1094920/ASTRO/Jupiter/Jupiter_20100922_MJA-AWB.jpg
>
> I left it as it's what I shot it as. I'm not 100% sure the real colors
> of most Astro Objects are either.
>
> http://en.wikipedia.org/wiki/File:PIA02873.jpg
> http://pds.jpl.nasa.gov/planets/images/browse/jupiter/jupiter.jpg
> http://b4tea.com/wp-content/uploads/2010/03/Jupiter.jpg
> http://www.solarviews.com/raw/jup/jupwsmap.gif
> http://news.nationalgeographic.com/news/2010/05/100514-science-space-jupiter-lost-belt-great-red-spot/
>
> The current crop of images have Jupiter more red than I see it visually.
>
> Later..
>
> Milton Aupperle
>