Some better conditions on Jupiter, why ?


In my last article Jupiter under the jet-stream, what’s the result? I described the effect of one the worst meteorological conditions for the seeing. During my last observing night of January 17th, images were noticeably better (although still not really good…). It is possible to find explanations?

Here are some Jupiter images taken during the night from January 16th to 17th, 2015. Resolution is rather satisfying in R+IR (long wavelengths are always a good plan when conditions are not good), mediocre in RGB and disappointing in methane. None the less it’s really better than last time!

On these images we see signs that the NEB has started a new classical revival phase of its life cycle. The RGB frame shows that its northern edge has become wavy, because the local jet-stream is now starting to undulate. An again most clear sign is the very dark spot visible at 284°/18°N: this is an anticyclonic vortex found in the NTrZ that is called “expansion spot”. dark clouds are going to fill in the NTrZ thanks to such spots during the coming weeks/months.

On Friday 16th, a rainy cold front is leaving France. Post cold front situations are usually bad for the seeing: low pressure and cold air in altitude favor strong convection (vertical loop movement). However, the sky clears progressively that day and the following night is clear. Refering to my article Five good conditions for astronomical seeing shows that an anticyclonic ridge is now passing over western Europe. The ridge is not very strong, but is still able to lower considerably the speed of the jet-stream:


GFS maps for the 17th at midnight. Left: ground pressure with the high-pressure ridge circled in red. At right, the corresponding weakening of the jet-stream.

Getting really good conditions would probably have required a more stronger ridge. Maybe nextime :)


Jupiter under the jet-stream, what’s the result?


Last year I made a summary on the best conditions for a good seeing. Unfortunately there are as well other conditions that damage it. Here is a “good” example on Jupiter: the influence of the jet-stream.

What is the jetstream?

The jet-stream is a very narrow, but very fast, stream of […] Continue Reading…


Prepare for the elongations of Venus in 2015: talk at RCE


Last week-end I gave a talk at the Rencontres du Ciel et de l’Espace (RCE) at Cité des sciences et de l’industrie in Paris, about Venus. The planet will be easily observable for northern amateurs in 2015, do not miss it!
In 2015, we will see two nice venusian elongations […] Continue Reading…


Different ways of using colors for imaging planets


The concept of color is often discussed among observers. The purpose of this article is not to debate about the concept of realism, but to describe and discuss the use of three ways to use color for planetary images : “true” colors, “false” colors, and colorized monochrome images…

The three […] Continue Reading…


The reference article about pro/am cooperation in planetary astronomy


Participating to scientific work when you’re an amateur observer, is that possible? Answer is yes! I have talked about it on several occasions on this blog, and here is a must-read on the topic if you’d like to get into that.

The adventure started two years ago during the “4th pro-am […] Continue Reading…


A possible new “high altitude cloud” observed


The most noticeable observation of Mars in the last 2012 season has been the imagery of what is generally interpretated as a cloud of very high altitude, because it was projecting well beyond the terminator into the night. Those phenomena look to happen regularly and many have been found […] Continue Reading…


Planetary mission at the Pic du Midi, 8-9th March 2014


On March 8/9th, I had the honor and pleasure to participate to a planetary mission at the 1-meter telescope of the Pic du Midi (T1M) lead by Marc Delcroix, President of the SAF planetary observations commission. Here is a summary!

The T1M of the Pic du Midi observatory is […] Continue Reading…


Observing Mars: some technical advices


After the article, “What can we see on Mars this year” let’s now review some technical advices.

Make images in true colors
The Martian details are quite unequals, between the sharp and contrasted surface details seen in red, and the faint, low-contrast clouds observed in blue light. As the most interesting […] Continue Reading…


What can we see on Mars this year?


Mars will be at opposition again on April 8th, 2014. Here are some phenomena you must look for!

Mars will be at opposition in one month and a half and is already finely observable since its apparent diameter has now passed 10″. It will reach a maximum of 15,2″ […] Continue Reading…


Interview: Yann Le Gall, planetary imaging with a large Dobsonian


Many instruments can be used to image planets. This week I’m portraying observer Yann Le Gall, who is making splendid images with large dobsonian on an equatorial platform !
Browse Yann’s homepage here!

Astrophotographie au dobson
Hello Yann! Can you tell us about you and your activity in astronomy?

I was born in […] Continue Reading…

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