Observing the major planets 2017.

When planets reach opposition ( opposite the Sun) they can be best observed and enjoyed. This also depends on how close or far they are at opposition. Currently Venus is very bright and low in the evening. Jupiter climbs high in the morning, but even x200 gives little detail as the disc is currently quite small. If we look at disc sizes , the full moon is half a degree across , 1800″. I have detailed disc sizes on the drawings.
2017 presents some oppositions, it’s not a great year.
Mars, May 22nd,opposition, but closest on 30th May.
Jupiter, April 7th, 01.14 size 44.2″
Saturn, June 15th, 11.05 size 18.4″
Neptune, September 5th, 01.07
Uranus , October 19th, 12.55
Conjunction , November 13th between Venus and Jupiter.img_4319

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With a great opposition detail can be easily picked up with a scope. Keep magnification to around x150, then increase it depending on seeing and transparency. Good nights and x200 upwards will give good details.Fall back to x150 and you’ll find the detail finer. At best , these are some features,
Mars.
Always a challenge, one side of the disc is fairly featureless, the other is packed. The rotation is 24 hours 39 minutes. Observing at the same time every night and you’ll not see much change. Better some early and late sessions. It’s orbit is very elliptical giving some close oppositions. By eye you can spot it as red. Through the scope , the rust red surface and darker sand areas can be seen. The polar ice caps can be very clear and May be observed as they melt in the spring. We’ve also seen other areas of brightness (albedo) such as frost in the Hellas basin. At close opposition , 4-6″ of aperture at x150 have given lovely detail.img_4295 X120-x150 are good starting magnifications. Then try increasing until you reach the limit that the seeing ( stability) and transparency will sustain good views. Reducing magnification you’ll notice details sharpen up again. Light cloud or haze can reduce the surface brightness , helping contrast . Reducing aperture using an aperture mask can help as can a range of filters. However nothing can improve a view degraded by poor seeing. It’s best practice just to leave the focus and wait for the detail to appear. Sometimes you’ll get a crisp view snap in and out. It’s not worth fiddling around with the focus, let your eyes, optics and atmosphere do the work.

Jupiter.
Perhaps the most interesting planet to observe. Every six years , the plane of the moons aligns with our orbital plane. Eclipses and occultations of the moons are frequent.This last happened in late 2014 and most of 2015.
Jupiter rises at 10pm and is on view all night long in February. In June it rises at sunset and sets at midnight.
The four Galilean moons dance around Jupiter adding to the planet’s surface details . The two main belts are dark brown often with festoons , tears and spots. Their edges change continuously. The Great Red Spot is in a pit in the southern belt. It’s appearance has varied from light rose colour to a dark red angry spot. There have been smaller spots both before and after the GRS. In 2010. The southern belt disappeared for a year, it was an eerie sight to see the GRS on its own.
In addition there are darker areas to the poles with fine belts here and to the equator.
Moons cross the surface, the shadows look jet black, with the moons themselves having the appearance of white peas. They are delightful to catch at the rim. Either before crossing or occulting. All such movements are transits. Times for transits are normally given for the middle of the disc. Apps such as “Jupiter moons ” give complete details of transits.
The rotation of Jupiter is 9.9 hours, you’ll notice changes over even a short session.Bands rotate at different speeds and often different directions. In this obviously flattened disc you never know what you can observe. We were talking to an observer who saw the impact of Shoemaker -Levy comet on the surface through a Dobsonian.

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Saturn.
The most stunning looking planet, but without the changes of Jupiter. The rings can be edge on or open right up from pole to pole. You should notice a dark storm band on the surface and polar markings.The rings should show the dark Cassini division, even at low magnification. Other zones may be visible under very good seeing. In May 2011 we saw the outer Encke and the inner darker ring at x400 on a very clear frosty night. The ring system of Saturn is very special, 99.9% composed of water ice it is between 10 metres and a kilometre in thickness. A yellow filter has added to details seen here. Titan, the largest of the nine large moons can be seen in a small scope. Under clear skies !

Nick.

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