JANUARY - FEBRUARY 2004

25 January 2004

First Jupiter images with the RAW mode of the B&W webcam (see Etienne Bonduelle's homepage). This modification improves noticeably the SNR of the raw frames, if one sets the webcam at the 5 fps rate. Images are so soft that the relatively small number of frames is not at all a problem.

The seeing is quite steady but unfortunately the sky is hazy - only the IR image is safe.

Here are also shown my very first attempts at using the ATK-1HS set in the long-exposure mode in order to obtain UV images of Jupiter. The haze was quite a problem here and the exposure was 1,5 sec for each raw frame ! Of course this lowers the quality of the images, but this first experience is promiseful.

Two set taken in the poorest conditions. On the 27th a snowshower even occurred, for the first time in year in my location. Under such conditions of course the only way to go is infrared. Images taken with the 7" newtonian.

30 January 2004

Conditions are corrects. The C14 is used along with a focal reducer and a 2x barlow to shorten the exposure in UV light to half a second "only", but also to help imaging in the other wavelenghts.

The three images are from left to right, RGB, UV, IR. The different responses of Jupiter in each wavelenght is quite striking. In UV the GRS is the darkest feature on the globe while it's almost white in infrared. In UV an "equatorial band" is also revealed just south of the true equator, not easily seen in the color image.

The feb. 5th images are taken with Gino Farroni's 16" newtonian (at a short focal so even in UV the ATK was in normal exposure mode !), and the feb. 10th images with the C14. The UV image at right is really good for the wavelenght.

These sets show the interesting region of BA and the South temperate current (STC). The high pressure is like followed by a dark and large STC segment.

14 February 2004

Again a correct night with the C14, but I'm more and more diappointing by the results.

The most interesting detail here is maybe the dark STB spot just south preceding the GRS. This cyclonic structure, strong in visible light, is almost invisible in infrared, as already noted on december 16th 2003.

A rift is forming in the NEB, some white clouds are well visible in ultraviolet, projecting above the UV-absorbing haze.

29 February 2004

I have decided to be back observing with the newtonian and the results are good. The sky is quite steady. Making UV images of Jupiter with this telescope is still possible at F/25 (against F/40 for the other images).

Here are presented an IR and a violet image showing the GRS and BA. Io and its shadow are visible on many images ; it's interesting to note its changing albedo with the wavelenght : very bright in IR, duller in visible light, it's very dark in ultraviolet.