International Year of Astronomy -
Astronomy now and then

Twilight will be with us all night here in the Northern Isles until August 19. In the absence of some unforeseen event, such as a bright comet or a display of the noctilucent clouds, one tends to look to the Sun, Moon, Mercury and Venus for “entertainment” from the natural summer sky.

The Sun has been in the doldrums now for over two years and as yet there are no clear signs of the commencement of the new cycle. Venus is currently at maximum brilliance (magnitude -4.5) for this elongation (maximum western elongation 45.9° on June 16). As mentioned in the previous Sky Notes, Venus is not well placed for naked eye observation until later in the year.

This, then, may be a good opportunity to compare the state of amateur astronomy now to what it was when I started out some sixty years back.

Fig. 1: Close up of the Cooke 132mm refracting telescope equatorial head. Note the size of the worm-wheel in RA (250mm diameter). Click on the image for an enlargement.

The first thing to say is that the range of equipment today is far and away more advanced than anything we had back in the fifties. Today even a basic refracting telescope of good quality may be purchased for a fraction of the cost (in real terms) and there is a far greater selection from which to choose including ultra high performance apochromatics and triplet lens systems (though the latter may set you back a bit in pocket!).

Fig. 2: The eye-end of the Cooke showing controls for clamping and slow motion in RA and Dec. (The drive itself has been altered from a gravity weight fall, giving two hours running time, to an electric 12 volt motor served by a mains transformer with battery backup

Much larger apertures may be achieved, as they always have, by the use of reflecting telescopes. There have been great improvements here too: the Cassegrain system is less cumbersome and more durable than the older open-tube Newtonians. A Maksutov-Cassegrain is a good compromise for those lacking the resources for an equivalent size in refracting telescopes, and it too is a good deal more compact than the refractor.

But the most significant advance has come from the developments in digital technology providing observers with the means of securing images of astronomical subjects unimaginable fifty years ago. Not only that, but everything has been speeded up – you can view your images as they are being gathered whereas film takes hours to process.

Fig. 3: Another view of the equatorial head. Note the circles in RA and Dec. The former reads to 5 seconds of time, the latter to 1 arc minute; both accessed via small magnifiers, the engravings on inlaid silver circles. Click on the image for an enlargement.

Telescope mountings have also been made more accessible in terms of cost and size. The equatorial head alone for my 1920s, 132mm Cooke refractor (Figs1 - 3) weighs over 70 kg – nearer 100 kg with counterweights. By contrast the shorter focal length (smaller “f” ratio) in modern refractors means that a comparable aperture may be mounted on a portable assembly such as that shown in Fig. 4.

Fig. 4: Skywatcher EG6 mount accommodating 100mm and 120mm apochromatice refractors of 900mm focal length. Note the electric power pack between the tripod legs. The system is portable and assembled in three stages onto pre-positioned location points.

However, a word of caution is necessary for those contemplating larger reflecting telescopes working outside in such places as the Northern Isles. In general fork mounts fitted with equatorial wedge plates are too unstable for serious work at high powers when exposed to anything more than a gentle breeze. [At the time of writing this article a force 10 gale is raging in the Westray Firth and here, on this sheltered east side of Rousay, I am reduced to a small 80mm refractor for observing Venus. (Fig. 5).]

Fig. 5: The same mount as in Fig 4 with the 80mm f/7.5 apochoromatic refractor. All quite stable even in a full gale! (May 07 2009 09h 15m UT.)

On the other hand, one advantage for most observers offered by these modern mounts is the addition of so-called “goto” software. Even the process of polar alignment has been simplified so that for the most part one does not have to understand the basic principles involved. And once set up all one has to do is master the handset, and then to press a few buttons in order to access an object from a large database.

And astronomy today (magazine publishers please note) is far better served by the media in general than it was in my youth.

As a result of these “improvements” observers may undertake more advanced work – much of it digitally recorded and stored. But for me there are two questions that need to be addressed. First, have modern techniques increased the observers understanding and pleasure? Second, has the visual observer’s contribution been downgraded?

There is a third and more fundamental question at the core to all this: what is it all for – what use can it fulfil? There is no short answer to that. We may think of ourselves as adding to the fund of scientific knowledge when we discover a new comet, an asteroid, a nova or what have you; certainly we are helping to expand the databases. In fact so vast is the assemblage of recorded “fact” that we have had to hand over its analysis to the computer itself. In a nutshell (a Hawkinsian concept?) the practice of astronomy has lead us into realms of conjecture and hypothesis only intelligible to a relatively small number of specialists.

I take the view that unless our science leads us to make humane choices in the use to which our knowledge is put then we might be better off without it. Our ability to tap into nuclear processes, for example, has led the world into a perilous condition - that cannot be denied.

Leaving aside all the changes in technology how does the more casual observer of the sky fare today compared to sixty or so years back? When in 1948 we moved into the Essex countryside from a London suburb the skies were dark at night and unsullied by aircraft condensation trails by day or night. When I left the same area in 1960 the night sky was an orange glow from sodium lighting and civil aircraft plied their way contributing to the formation of high cirrus cloud.

Much the same pattern has followed worldwide and Orkney offers no more the pristine, clear skies it did back in the seventies and early eighties. From my home on Rousay there are literally hundreds of lights visible on the other islands and from the sea – no longer is the Milky Way visible from horizon to horizon on a clear night. And in the near sky, artificial Earth satellites are in abundance turning constellations into contorted depictions of themselves.

Things have changed. For good or bad depends upon your perspective. The main thing IS to enjoy what is still a minority pursuit and to pass on one’s enthusiasms as best we can, often under challenging circumstances.

JV 05/05/09