Alan Willison, of Hertford Astronomy Group, looks at telescopes — and explains what you can see with them in his latest guide to astronomy.
Hands up. Who has got a telescope sitting under the stairs (or other suitable location) that isn’t being used?
Maybe the reason that it is there is because it didn’t seem to do what you thought it might or just that you couldn’t see anything through it.
Well, rest assured you are not alone.
Lots of people buy a telescope thinking that:
- It would be straightforward to use, and
- It would reveal the wonders of the universe from your own back garden.
In reality, neither of those statements are true yet you are not far from getting it right. So, how do we bridge that gap between the reality you experienced and getting some enjoyment from your purchase?
The first step is to have a reality check on your expectations.
No telescope will show you those wonderful colour views of nebulae clouds or the swirling shapes of other galaxies.
The reality is that they will both look like a smear of mist through a telescope eyepiece — just as if someone has breathed on a piece of glass. That’s if you can even find them.
No telescope will show you the constellations. You will be able to see parts of them but not the whole thing.
Stars will look like a white point of light with no dimensions — that’s if the ‘seeing’ conditions are perfect. Frequently they will look like an animated microbe which is the effect our atmosphere has upon what you are looking at.
Well, what will you be able to see then? All telescopes, whether you bought one for about £75 from Aldi or £7,500 from an astronomical shop, will show you details on the Moon. You will be able to see craters, mountain ranges, valleys and other geographical features. The views will take your breath away.
All telescopes will show you the four Galilean moons of Jupiter — Io, Callisto, Ganymede and Europa. They orbit the planet so quickly that the view will change from night to night — or even on the same night. As well as those moons you will be able to make out two bands crossing the planet which has now changed from looking like a bright star to a disc. Indeed, another wow moment.
All telescopes will let you see the rings of Saturn. This is undeniably a well designed planet that will fill you with awe and wonder. If it doesn’t then astronomy is clearly not for you.
Mars will also transform from a star like object to a disk with a reddish hue. If you are lucky, you might be able to tell that that it has ice caps rather like the Earth. These ice caps change in size according to the seasons again, just like ours do.
Venus will change from a brilliant star like object into a white disk but, as it is closer to the Sun than us, it shows itself like the Moon with phases like a full Moon, half Moon and new Moon. No surface detail is possible as it is covered with dense white clouds.
Mercury is also visible but viewing has to be cautiously approached as it is closer to the Sun and is only ever seen in the twilight and no telescope should be pointed towards the Sun as accidents can cause blindness.
You should be able to split some double stars into their individual components —Mizar (the second star in the handle of the Plough) is a good target for this.
Star clusters will transform from specks into images that have often been compared to seeing grains of salt sprinkled onto black paper.
With all those reality checks taken on board you can now start thinking about your telescope, especially if you haven’t had much success with it.
A question we often ask enquirers is what does a telescope do. A frequent answer is that it magnifies the object we are looking at.
Wrong. The right answer is that telescope collects light.
Here’s an analogy for you to consider. If you wanted to collect rain water for a short time would you use a bucket with a wide opening or one with a narrow opening? Hopefully you said the one with a wide opening as it covers a wider area.
It’s the same with telescopes — the wider it is the more light it collects. The telescope brings all that light to the eyepiece which is the part that does the magnifying.
One of the most frequent questions we get asked at events is, “How much does it magnify?”. The expectation is often that the higher the number the better. This is definitely not the case.
The more that an object is magnified the more you have to spread the available light out. This means that the image gets dimmer as you magnify it.
Another consequence that isn’t thought about until you try it is that the more you magnify an object the more everything else gets magnified — the vibration of touching the telescope can send the image darting about wildly so that you can’t focus it satisfactorily.
Another consequence is that the rotation of the Earth will make your image disappear from view in moments as it drifts across you field of view. Telescopes are often fitted with devices to help them track targets and keep them in the eyepieces.
That’s a start about why your telescope isn’t working but there can be lots of other reasons that there isn’t room for here, so how can we help you further?
Well, on Saturday, March 16, Jerry Stone will be giving a practical talk and demonstration entitled 'My Telescope Doesn’t Work' at the Bramfield Village Hall, SG15 2QL.
You can bring your telescope along and we will help you to get it working and even better, it is free to attend! You can register your interest at our club website https://hertsastro.org.uk and we will try to make you and your telescope the best of friends and go out a bit more often.
Photo of the Month
Taken by Hertford Astronomy Group member Stephen Heliczer
"I took these pictures from my garden in Cuffley.
"The picture is a montage of various sessions of solar system captures including the Moon and Tycho crater, Venus crescent, Mars, Saturn, Jupiter, and Uranus.
"You will be able to see many of these stunning celestial bodies with a relatively cheap telescope if you know where to look!"
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