[AZ-Observing] Re: [amastro] blue festoons on Jupiter (in small aperture)

15480 Empire Rd.
Benson, AZ 85602
hm ph: 520-586-2244
I just got back in from observing Jupiter with my 13-in f/5 Dob. It is now 
midnight local AZ time and the impact site is an hour or so past meridian. I 
was using a 7mm eyepiece and the seeing and transparency were pretty good. I 
don't know about seeing draping festoons, but I definitely saw a nice navy blue 
barge on the south side of the NEB, if that makes sense, at about the same 
longitude as the impact site and I have seen white ovals near north of the 
site. It was elongated horizontally and appeared denser than the impact site 
which appears to still be bi-nuclear with the north-following element still 
smaller and denser than the south-preceeding element, which has always been the 
case in my several visual observations. I don't know if it was because of our 
moon's light pollution causing a loss in contrast, but the impact site seems to 
possibly be fading since my last observation the night before. The NEB is very 
textured with lots of swirls and eddies in it, while the SEB, other than the 
area with the Red Spot and its attending barge, seems to be fading and fairly 
featureless. 
I also enjoyed the dance of the inner Galilean moons tonight. When I first 
started observing Jupiter earlier in the evening, two of the moons were very 
close together, one probably had just occulted the other, which I missed, but 
the movement among Io, Callisto, and Europa was very evident in the couple 
hours that transpired during my observation of the Jovian system. 
BTW, I tried observing Jupiter with my 4-inch Astroscan. While this telescope 
is great for wide-field views, it is not a planetary scope. The moons are 
obvious, surface detail on Jupiter was not. 

Clear skies, 
Wayne (aka Mr. Galaxy)


---------- Original Message ----------
From: "gnowellsct" <tim71pos@xxxxxxxxxxx>
To: amastro@xxxxxxxxxxxxxxx
Subject: [amastro] blue festoons on Jupiter (in small aperture)
Date: Fri, 31 Jul 2009 01:28:42 -0000

  I see blue festoons on Jupiter in my 14" routinely, but had thought that 
"color on Jupiter" was generally a product of aperture. In my small scopes (4" 
and 5" doublets, one ED, the other fluorite) Jupiter generally yields to 
brownishness.

Monday night I caught the Jupiter impact spot with a few club members who were 
relishing a rare clear sky here. I had given up on any chance of seeing the 
impact site but there it was.

Approximately where the impact site crosses the meridian, further N, there is a 
complex of blue festoons in the equatorial region, draped, as it were, from the 
NEB. I was quite surprised to be seeing these in my FS128 and I was skeptical 
of my own observation, thinking that I was seeing perhaps some grayish streaks 
and that I was "painting" with my imagination. The blue festoons were, as they 
are typically but not always, closely associated with the NEB. I have detected 
festoons in my 4" refractor but more as grayish streaks; it would never occur 
to me to call them blue, had I not seen the color in larger instruments.

I was using XWs and ZAO IIs both of which are known for accurate color, 6mm, 
5mm, 4mm, and 3.5mm. In the 3.5 and 4mm the color was very hard to make out (as 
is typical). 170 to 200x seemed pretty good for the festoon color. Since the 
impact spot is much photographed I had no problem finding a recent amateur 
image and verifying that there was indeed a complex of blue festoons where I 
had observed them. 

I was wondering how many other people have seen blue festoons in small 
apertures, what the apertures were, and what magnifications were used. I'm also 
curious about detection of red/pink in the GRS vs blue. We have least 
sensitivity to red wavelengths at night but the red does travel best through 
the atmosphere. I'm unsure how the biology of the eye and the physics of light 
transmission work in this case.

thanks
Greg N 


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