Archive for September, 2010

Two on Jupiter

Sept 24th 2010

Last night was unexpectedly clear and after enjoying a meal in a local restaurant with a few astronomer friends my optical boffin pal Es Reid of Cambridge spent an hour or more studying Jupiter close to the blazing full moon.

We used both the observatory 20” F3.7 reflector stopped down to 8” with an off axis mask giving an unobstructed view and simultaneously observing with the 153mm (6”) piggy backed triplet refractor.

This was great fun with both of us being able to observe exactly the same detail through identical local seeing conditions.

The refractor had the edge on sharpness and darker background but the 8” reflector view was more comfortable and detail easier to discern. Added to this the fact the reflector was running a Denkmeier binoviewer. Both were hitting around 180x and detail was occasional good in the fast seeing.

We both observed and agreed that focusing on the Galilean moons and getting then sharp did not give the best focus on the planet itself! Interesting.

Before we closed down the observatory we viewed Uranus just a degree to the north, both scopes showed a nice bluish disc, to me the colour was stronger in the refractor.

We studied the view hard for any hint of moons close to the planet but saw none. Removing the mask and allowing full 20” plus aperture had the disc doubling and trebling but still no moons were seen.

Great fun, Dale

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