Martin Dawson joined the York Astronomical Society in
1973 shortly after the society was formed and has been a member ever since. He
kept an occasional diary of events from that time. Some of the entries bear a
similarity to current happenings at the Society: meetings, talks and working
parties at the observatory, then at Acaster Airfield. An example entry:
7 Jan 1977 – ‘YAS Member Mrs. Gibson presented her talk on her trip to West Africa to see the 1976 October eclipse. 0.90p made in raffle (1.75) Planisphere as prize.’
York Astro member Martin Dawson, has sent us a copy of the Society’s newsletter from 1974, two years after the Society was formed. Although the newsletter was printed on old technology with hand drawn illustrations, the topics covered would be familiar to members now; reports on recent talks, what’s to be observed that month and progress with the observatory. Back then, meetings were held at the Railway Institute and planning permission for the observatory had been obtained, plus the Society has acquired a 12.5″ reflecting telescope – wonder what happened to that.
Inclement weather threatened us at the start of the day, but
it eventually turned sunny. There was a good turnout of volunteers and a number
of tasks completed. After setting the world to rights we started work. We were
refuelled at lunchtime by some great bacon and sausage baps from Angela.
Talk by David Cook at Priory Street, 1 March 2019.
There is more to sundials than things plonked in a garden on screwed to a church wall and you would be surprised how accurate they can be.
David presented an interesting talk for the Society at the Priory Street Centre on Friday 1 March. He started out by saying that sundials are ‘rubbish’ and then went on tho show that a lot of them aren’t, demonstrating a range of different sundials from his own collection. Continue reading →
A monthly look at astronomical events in the sky and on Earth
The following article often refers to angles in the sky. The diagram above is a rough guide. Hold your hand at arm’s length. (Courtesy of timeanddate.com)
A rare opportunity to catch a naked eye glimpse of elusive Mercury in the evening sky after sunset. Find a place where you’ve got a good view of the western horizon, note where the sun sets (at about 1740), wait until 1815 then look at a point 10° directly above where the sun set and there will be Mercury. Binoculars will help you to spot it initially but it’s easily visible without them. A small telescope will show it as a 36% illuminated orange coloured crescent. It’s visible until after 1845 as it slowly approaches the horizon.
BEWARE! Don’t try using binoculars to scan the sky for Mercury before the sun has completely set. You could blind yourself!
If you’ re awake by 0615, look low in the SE to see Venus and the crescent Moon together just 5° above the horizon. A nice sight.
A wafer thin crescent Moon appears in the WSW after sunset (1754). It’s only 4% illuminated so will be a challenge to spot but it’s worth a try. By 1830 it should be easier to see, and Mercury may still be spotted at 5° altitude due west.
The waxing crescent moon passes near to Mars. Spot the red planet 3° above and to the right of the Moon any time from 1900 to 2100 in the SW to W.
Moon at first quarter. This is a great time to observe it, as the terminator is facing us and throwing lunar features into sharp relief.
Objects of the Month
There follows a shortlist of objects that are roughly in the south this month at 2030 hrs – a convenient time for family viewing.
The image above shows the sky at about this time, looking south (from Stellarium).
Castor and Pollux
The “heavenly twins” and the two brightest stars in the constellation of Gemini.
A 2 or 3-inch telescope will show Castor as a double star (separation 4 arc seconds) but in fact each of those stars is itself a double, discovered spectroscopically as they are too close to be separated optically. Each pair comprises a hot, bright A-class main sequence star orbited by a cool, faint M-type red dwarf. What’s more, this pair of doubles is orbited by another very faint double, making Castor an amazing 6-star system. Its combined magnitude is 1.58.
While your telescope is pointing at Gemini, take a moment to look at Pollux. Its orange colour is clearly very different from that of Castor. Pollux is a giant K-type star nine times the diameter of the Sun but only twice its mass. At 34 light years distant, it’s the nearest giant star to us. It does have a planet at least twice the size of Earth orbiting it called Thestias. Unfortunately, at only 1.6 astronomical units (a.u.) from the star when the habitable zone round Pollux is between 6 and 12 a.u., life on Thestias could be a tad challenging!
The Winter Triangle (Procyon, Sirius and Betelgeuse)
These three interesting stars form a near-equilateral triangle. See star map above.
SiriusThe brightest star in the sky. Is actually a binary. Sirius A is a main sequence A0 star; Sirius B is a white dwarf hundreds of times fainter than Sirius A. Although their angular separation is currently 10 arc seconds, the difference in brightness (magnitudes -1.44 and 8.5) makes spotting Sirius B a challenge for even large telescopes. The Hubble image on the left illustrates this.
Another binary star. Procyon A is an F5 star and thus cooler and yellower than Sirius. Procyon B is another white dwarf. Their magnitude difference and closer separation (4.3″) makes spotting the fainter component even more difficult than for Sirius but Giuseppe Donatiello has done it with a home made 127mm f/9 ED refractor!
Now Betelgeuse is something quite extraordinary. It’s an M1 red supergiant and one of only a handful of stars that are large and near enough for specialist telescopes to see their surface as a disc. This is a NASA image. Put it where the sun is and it would extend nearly to the orbit of Jupiter. It’s a semiregular variable whose magnitude changes by 1.3; its surface temperature is only 3600K but it’s luminosity is 90,000 to 150,000 times that of the sun.
And finally, two Open Clusters, M41 and M47
These often neglected clusters are fine targets in modest telescopes and even binoculars. M41 is 5° below Sirius, and M47 is 12° east and 2° north of Sirius. They’re both at magnitude 4.5 and about the apparent diameter of the full moon. Note that M41 contains a mixture of red giants and white dwarfs but M47 comprises mainly young blue stars and only a few red giants.
Stop press – space news
As this item is being uploaded, we have news of the successful launch of Israel’s Beresheet lunar lander. This privately funded mission by Israel’s SpaceIL company lifted off using a SpaceX Falcon 9 rocket. The name Beresheet comes from the book of Genesis and means “In the beginning”. Clearly, Israel intends this to be the beginning of their efforts in space. For the latest news, see this Sky & Telescope article and this Beresheet fact sheet.
People in York (well, those prepared to be up through the night) were rewarded with a spectacular view of the lunar eclipse on Monday morning. I feel sorry for some I know who got up through the night and see clouds, only to go back to bed to miss the spectacle when they cleared. Continue reading →
The remaining Portakabin unit has been dismantled and suitable materials recovered for recycling or appropriate disposal. The remaining rotted wood has been burnt. Here you can see Martin Whipp in nostalgic mood watching the burning embers – Martin was there at the beginning and at the end. Continue reading →
Disappointment, Pride, Frantic, Tension, Emotional, Fantastical and Cloudy. Just seven words that sum up September for YAS
Thursday, September 6th
We learn that the Planning Officer is recommending refusal for our planning application for the move of the Observatory to Beetle Bank Farm. It is disappointing that they do no recognise the special circumstances for locating in the Green Belt.