Saturday, January 25, 2014

Revisiting Jupiter

South is at top

Tonight's observation started at 21:30 and lasted till 22:45 local time. The lower atmosphere was turbulent with light to moderate winds and 2 Oktas of cloud coverage, which increased with time. These conditions resulted in general poor seeing, however at the native f-ratio of the scope, an acceptable IR-RGB image of Jupiter was possible as shown above. It is apparent that the most useful channel is the IR (an Astrodon 742nm band pass) band, which is less influenced by atmospheric turbulence.

What can we observe from the IR-RGB image?

1. The GRS (measured to be 23,527 km in diameter) has a light colour at 742nm, but seen dark through the Blue filter, meaning that the light is being blocked by the B filter. So light having a longer wavelength is being highly reflected from the GRS. A delicate internal structure is evident within this gigantic anticyclonic storm.

2. Light reflected from a spectacular array of festoons is not passing through the IR, R and somewhat by the G filters, but instead is being transmitted through the shorter wavelength Blue filter. Under very good seeing, a UV filter would probably further enhance these elements, as shown by the images produced by Chris Go.

3. The SEB is darker in IR than the NEB, the latter being less defined. Three white ovals (L1=240deg), which are lighter in IR are rising on the right (South is top) of the STB.

4. Io (L1=180deg) is shown as a brilliant white globe through the IR than the B filter, casting a defined spherical shadow on the SEB.

Below is the image shown in a cylindrical projection.

South is at top

High resolution imaging

The effects of poor seeing conditions were much pronounced when the planetary camera was set at approx. f/25 (see image below). Similar results were obtained by Chris Go taken on the same day but during different time from his observatory.

Nevertheless, general features can be seen (according to BAA nomenclature):
  • The GRS is very prominent, and setting on the right, followed by a highly chaotic area in the SEB.
  • At least 4 NEBn colliding Barges are visible in the NEBn at the central meridian. Apart from Io's shadow, these barges are the darkest features on the planet. These dark cyclonic circulations can persist on the NEBn edge.
  • White plumes and a major elongated rift are visible in the NEB. 
  • Image displays a spectacular array of dark Festoons (especially prominent in the IR image above), which are visible emanating from the southern edge of the NEB.
  • Possible presence of jetstream marks on the southern edge of the SEB, which would have a more distinctive appearance under better terrestrial weather conditions. 
  • Three white ovals are rising on the left within the STB; the main elongated one could be the Oval BA. 
  • Stereographic polar projection from the South Pole shows the position of GRS at L2=210deg. 
North is at top

View from South pole

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