ph . Podcast . Northern Sky Talk

Episode 2: May 2008

Posted 2008 May 04 @ 13:19 - filed under Podcast

Download current episode May 2008 (11.7 min, 4.8 Meg)

This is Northern Sky Talk, giving you a northern perspective on the night sky. I am Karol, broadcasting to you from Europe.

Imagine a sky where you can never see Sirius and only the upper half of Orion is sometimes barely visible above the southern horizon. Welcome to central Europe around 12,000 BC. We owe this almost magical opportunity to see exotic constellations to the phenomenon called precession. If we moved back in time to around 12,000 BC, our north star would be Vega and we would end up loosing such familiar sights as Sirius and even Orion's belt. However, we would also gain such constellations as the Southern Cross, Phoenix with nearby Achernar and even have the Small Magellanic Cloud just peeking over the horizon. Even though we cannot venture back in time to see the European sky like this, we may one day find artefacts created by some ancient culture who did. Also, the very ancient Indian epic Mahabharata mentions Vega slipping from its high position in the sky to become the pole star. Coming back to the present, in May the Southern Cross is getting reasonably visible around 10 p.m., starting at latitude 20 degrees North in places such as Mexico or India. However, if you would like to see the Small Magellanic Cloud as well, it is advisable to travel closer to the equator, at least as far as Cayenne in French Guyana or Brazil where you can easily enjoy the wonders of both northern and southern skies.

In May you can still view Saturn after sunset, slowly sinking from an altitude of about 50 degrees as seen from Europe or slightly more than 40 degrees as seen from Cape Town. It is worth trying to get a last good shot at the rings since we are slowly closing in for a ring plane crossing which is due to occur on 4 September, 2009. In the mean time, Mars is slowly approaching Saturn in the sky and the two are going to be closest on 10 July. Then on 4 September 2008 Saturn will enter solar conjunction and the show will be over this season with the planet reappearing on the other side of the Sun later this year. By the time of its next opposition on 8 March 2009, we are going to see really narrow rings. And because the closing rings are also reflective, its overall brightness is going to be considerably fainter. However, the moons will pop up more easily, with less glare from the planet.

The Moon will appear close to Mars on 10 May followed by Saturn on the 12th and Jupiter on the 24th. While taking a look at that, do not forget to examine the surface of the Moon itself. There is a certain aspect of art and adventure when you try to explore the wonderful places you can see there. If you really want to test the resolving power of your equipment, try it on the western rim of Mare Crisium in the vicinity of the crater Proclus, where you can see a feature resembling a "gate", formed by two facing mountain ridge promontories called Lavinium and Olivium. Some observers reported an illusion of seeing the so called O'Neill's bridge connecting them. Try seeing that live through your telescope when the Moon is 4 or 18 days old. A much easier feature available to binoculars of all sizes is Mons Piton. It casts a very sharp, long shadow and will seem ridiculously steep when you view it on a 7 or 22 day old Moon. But it in fact elevates only 2250 meters above the plain of Mare Imbrium and is rather spread with base diameter of about 25 km. When the Moon is near full, try Messier and Messier A - a pair of craters about 10 km each, accompanied by a double trail resembling a tail of a comet. Another feature whose steepness is strongly enhanced by shadows is Rupes Recta. It is 120 km long and its maximum height reaches about 300 meters with a true steepness of only 41 degrees. 8 days after New Moon it can easily be seen as a black line. However, when the Moon is 23 days old, the wall becomes very reflective and turns white.

This podcast was recorded on May 2, 2008. The podsafe music used for today's show was created by Solace. Take the best of care and clear skies!

Episode 1: October 2007

Posted 2007 October 27 @ 13:45 - filed under Podcast

Download episode 1: October 2007 (10.5 min, 4.3 Meg)

This is Northern Sky Talk, giving you a northern perspective on the night sky.

No one would have believed in the last years of the nineteenth century that this world was being watched keenly and closely by intelligences greater than man's and yet as mortal as his own; that as men busied themselves about their various concerns they were scrutinised and studied, perhaps almost as narrowly as a man with a microscope might scrutinise the transient creatures that swarm and multiply in a drop of water.

With infinite complacency men went to and fro over this globe about their little affairs, serene in their assurance of their empire over matter. No one gave a thought to the older worlds of space as sources of human danger, or thought of them only to dismiss the idea of life upon them as impossible or improbable. At most terrestrial men fancied there might be other men upon Mars, perhaps inferior to themselves and ready to welcome a missionary enterprise.

Yet across the gulf of space, minds that are to our minds as ours are to those of the beasts that perish, intellects vast and cool and unsympathetic, regarded this earth with envious eyes, and slowly and surely drew their plans against us. The immediate pressure of necessity has brightened their intellects, enlarged their powers, and hardened their hearts.

The War of the Worlds
H. G. Wells

I am Karol, broadcasting to you from Europe. Bandwidth for this podcast is kindly provided by Auke Slotegraaf, the creator of the regular Southern Sky Talk.

Unlike in the southern hemisphere, Mars is placed favorably in the northern sky. In Warsaw, Poland it rises before 8 p.m. and at midnight it can already reach an altitude of at least 35 degrees above the horizon. On 1 November its visible size will have exceeded 12 arc seconds and its brightness will reach a negative magnitude 0.6. Around mid-November Mars will start moving backwards among the stars on its way to opposition which will take place on the 24 December.

On the night of October 27 to 28, the Moon will cover the Pleiades as seen from Warsaw in Poland and many other parts of Europe. Three minutes past midnight the first of the named Pleiades, Caeleno, will disappear behind the sunlit limb. Almost an hour later they will start reappearing from behind the dark side. In Cape Town the viewing angle will be different and the Moon will simply miss the Pleiades, merely passing by this beautiful open cluster. Nonetheless, it is always worth examining the surface of the Moon in search of interesting features. It is far too easily forgotten that the Moon is a world on its own, with its rocks, hills and valleys revealed by light and shadows.

In late October two bright comets graced the northern sky. On 24 October Comet 17/P Holmes made history brightening from magnitude 17 to magnitude 3. In a matter of hours it was transformed from an obscure object to a memorable comet easily visible even in large cities suffering from severe light pollution. To the naked eye it appears like an additional star in Perseus. In a telescope that star turns into a yellow disk with a glow slightly off centre and a greenish fringe visible even under heavy moonlight. It is currently 2.4 AU from the Sun and unlike close bright comets it won't move a great deal among stars. Throughout the first half of November it can be found between the stars Lambda and Alpha Persei. According to John Bortle, this sudden brightening of Comet Holmes may have been caused by a crushing collapse of a honeycomb structure developed in some region of its nucleus and not by impact or fragmentation.

As of late October, Saturn won't rise until 1 a. m. but towards the end of November it will already be visible low over the eastern horizon around 11 p. m. Galileo was deeply troubled to see the rings of Saturn as artifacts resembling handles or human ears but even a 4-inch telescope reveals them as a ring fully detached from the planet. It is one thing to see the rings in colourful photos, but seeing them live in an eyepiece as something real in the sky has a much greater impact on our perception. Since Saturn exited solar conjunction way back in late August, its visibility is going to improve over the following months.

This podcast was recorded on 26 October 2007. The podsafe music used for today's show was created by Christopher of the Wolves, Solace, Kitka, Falik, Ya Elah and Hybris.

Take the best of care and clear skies!

Comments?

Questions or comments about this edition? Contact Karol by sending an e-mail to karolp6yahoo.de

Keywords: Astronomy, podcast, Northern Sky Talk