Ganymede's Shadow Transit 4th Jan 2015

[Qualia]

A Little Observing Guide for Newcomers

Last night was crisp, clear and calm but with an almost 100% illuminated Moon beaming down I saw little point rolling out the 10" and go hunting for deep space objects. Instead, in light of quite a few posts this week raising questions about observing Jupiter and how one could possibly garner more detail from the planet, I thought it would be an idea to try and sketch Jupiter as I saw it in the eyepiece, as it may appear at first glance.

Appreciating that most of the enquiries were made by those with 6" telescopes or less, this gave good reason to carry out my new toy , the small TV 76 and see what was possible. Again, although the skies were calm I didn't want to throw too much magnification at Jupiter, figuring that around 100x was a happy medium for my eye, the telescope and the average magnification many newcomers would be using. In short, I just wanted an average session, under reasonably good conditions of seeing and with a small but decent scope and quite a basic eyepiece that certainly don't break the laws of physics .

I have such a clumsy hand that it would be impossible for me to draw any of the detail seen on a small disc about 8mm across, that is, the general size I saw Jupiter within the eyepiece. As such, I drew a large circle with a radius of 4cm, sketched in what I saw using soft b-graded pencils and then reduced this image, added colour and softened the features with the free software program, Gimp 2. The result, I hope, is a more or less accurate impression of Jupiter as seen when one glances at it though a small telescope.

The trick of observing Jupiter, then, as it is for all celestial objects, is to go beyond this casual looking. Within reason, more aperture would offer the promise of more resolution but even with a small 3" scope, one can discern more detail as one spends more time at the eyepiece. If we slow down for just a moment, the first noticable feature in the sketch are two of Jupiter's moons, in this case Io and Callisto. We are also able to see Ganymede's shadow transit close to the western limb and we can make out the north and south temperate zones, the north and south tropical zones, the equatorial belts and the equatorial zone.

With a little more attention and the help from Ganymede's shadow transit, for example, it is clearly noticeable that Jupiter rotates quite fast, from east to west. We can also see that the planet isn't quite a perfect disc, there's a slight flattening at the poles. We are also able to discern subtle colours on the disc itself. Mellow hues of blue and grey, light and dark browns and even organey-reds. And although the shrinking of the sketch has rendered them virtulally impossible to see, at the eyepiece, between the cream coloured zones and the darker belts you can tweak out numerous irregularities. Not only within the belts themselves as we witness the phenomenon of ever-changing cloud features, but also dark greyish festoons and quite possibly lighter plumes located near the planet's equator. On another occasion, Jupiter's Great Red Spot - which is quite pale this year - will also be possible to observe.

You are guaranteed never to see the same view twice. Jupiter really is very dynamic, making it the most interesting planet to observe in the night sky. As such, the more time spent at the eyepiece, the more skilled you will become at seeing Jupiter's very subtle but very beautiful features.

[mister_wavey]

fab post, thanks Q!

[michael.h.f.wilkinson]

Very nice report with some great advice. I had the APM 80mm out yesterday, but early in the evening the view of Jupiter was blocked by a hedgerow, and even when it cleared that the seeing was awful

[Pondus]

Great post!

This must be one of the best "what to expect to see..." or  "Jupiter through a small telescope"  illustrations there is.

Fabolous  .

Rune

[Astro Imp]

You've excelled yourself here Rob.

All the newcomers who query what they are seeing (or not seeing) on Jupiter should be directed here.

[Qualia]

Thank you all for your kind words. It was good being out last night and I hope the post serves as a general idea for new observers; that even with something apparently 'small' and so far away, with a little relaxed concentration many treasures can be sought .

[ghostdance]

Kudos Qualia Another great post and sketch - pretty much what I mostly see in my humble 6", although as you say, the great thing about Jupiter is he's always introducing subtle changes in his wardrobe so is always rewarding us.

[cotterless45]

Brilliant Rob !

Nick.

[mariosi]

Very nice observation report Rob!

Thank you for sharing and clear skies always.

Marios