Posts Tagged ‘telescope’

A New Supernova in M99?

January 29, 2014 Leave a comment

After the discovery recently of a supernova in the Cigar Galaxy, M82, it looks like we have another supernova candidate in a different galaxy M99.

Seen just three days ago, astronomers are still trying to work out whether this is indeed a supernova; it should be confirmed soon.

It’s been measured at magnitude +15.4 recently, much fainter than the nearby supernova in M82, which currently stands at brighter than +10 (over 100 times brighter).

You’ll catch the supernova in M82 using just a modest telescope, while the new potential supernova in M99 you’ll need a big scope to see it.

Happy supernova hunting!

UPDATE: It’s been confirmed as a supernova and has the designation SN2014L


John Dobson, “The Sidewalk Astronomer”, 1915-2014

January 16, 2014 2 comments

John Dobson, known as “the sidewalk astronomer“, and the inventor of the Dobsonian telescope mount, died yesterday 15 January 2014.

John Dobson, 1915-2014

John Dobson, 1915-2014

I had the pleasure of meeting John back in 2006 when he visited Glasgow Science Centre to give a talk in the planetarium. As planetarium manager at the time I was in John’s company for most of the two days he was in Glasgow, and became well used to his unorthodox – and mischievous – teaching style.

“How many stars are there in our solar system?” he asked, with a twinkle in his eye.
“One…?” I ventured, smelling a trap.
“Actually there are three. Jupiter and Saturn are stars too. They define a star as something that emits visible light. But Jupiter shines in infra-red; it gives off more than twice what it takes from the sun, but astronomers don’t see that, because they’re too retarded. You see, that’s the problem with talking to me – I throw you a curve ball.”

His most controversial views were regarding the Big Bang Model. It’s fair to say that John wasn’t a believer* – he told me he was “allergic” to it! He instead promoted a steady state model, where the receding galaxies “fell off the edge” and got recycled back in… To be honest I didn’t really follow his arguments too closely, but there’s no doubting the entertainment of his delivery.

Certainly the audience who came to Glasgow Science Centre’s planetarium to see John talk were thoroughly entertained. Perhaps not in a very orthodox way, nor with theories that were widely accepted in the astronomy community, nor indeed about what they thought they’d hear John speak about. The talk had been billed as “hear John Dobson, inventor of the Dobsonian telescope mount, talk about his revolutionary design and his passion for sidewalk astronomy”. He gave that five minutes at the start of the talk; the rest was non-standard cosmology and poking fun at the consensus.

He didn’t credit himself as the inventor of the Dobsonian mount. After all, astronomers had been using elements of it for a long time before John put them all together and began popularising this low-cost mount.

A Dobsonian Telescope Mount

A Dobsonian Telescope Mount

A Dobsonian mount is effectively a spinning plate with a cradle on it for holding the telescope. The plate spins allowing you to move the telescope from side to side (the azimuth co-ordinate, in astronomy speak) and the telescope can tilt in the cradle allowing you to move it up and down (the altitude co-ordinate). This is a far simpler mount than the alternatives, and can be built out of everyday items at low cost, meaning that more of your budget can go on the telescope tube itself, building larger tubes to collect more light (we call these large telescopes “light buckets”) and so get clearer, sharper images.

John himself never called them Dobsonians, instead referring to them as “sidewalk telescopes”. “For hundreds of years, wars were fought using cannon on ‘Dobsonian’ mounts; it’s nothing new,” he would say. But his design was innovative, and it brought the universe a little bit closer to us.

My primary telescope – the Skywatcher 250 PX – uses a Dobsonian mount. It’s an ideal scope for public astronomy events as it’s very quick to set up, and is really easy to operate. Want to move it? Just nudge or pull it.

John’s mount, and his passion for showing people the universe through a telescope, led to his popularising of “sidewalk astronomy”, which involves standing with a telescope out in a busy street in your town and showing passers-by views of the cosmos. Of course due to light pollution in towns and cities you’re limited as to what you can show, but the Moon and planets are easily visible from wherever you are. If your unsuspecting passer-by has never seen the rings of Saturn, or the moons on Jupiter, or mountain ranges and craters on our own Moon, you can be sure that their few minutes with your telescope will amaze them.

John Dobson will be remembered as the grandfather of sidewalk astronomy, but I’ll remember him most fondly as the very eccentric and enthusiastic man that I spent a couple of days with in Glasgow in 2006. The most vivid memory I have of John is taking him out for dinner the night he arrived in Glasgow, as I did with all visiting speakers. He didn’t eat meat, he informed me. And he didn’t eat processed food in restaurants. He saw that I was beginning to look worried. I suggested he might like a salad. With a grin he said “Why pay for a salad when there’s perfectly edible stuff just laying around?”, at which point he began rummaging in the flowerbeds for edible plants and weeds…
* Not that I’m a believer. I don’t believe in the Big Bang, rather I accept it as a model for the universe which fits all of the observations that we make. It’s true, to the limits of our current observations.

Happy Birthday Hubble! Top Five Spring Telescope Targets

April 23, 2013 Leave a comment

The iconic Hubble Space Telescope (HST) was launched 23 years ago on 24 April 1990, and ever since has been returning breathtaking images of the cosmos as well as world-changing science. It is, without a doubt, one of the most successful scientific instruments ever built.

To celebrate its 23rd birthday here is a list of five stunning celestial objects visible over the next couple of months that you can find for yourself using a small earth-based telescope. Most of these objects will look like nothing more than diffuse grey smudges in the field of view of your eyepiece, but I’ve illustrated this post with some HST images of the same objects, to show you what they really look like. Despite the fact that your telescope can’t ever show anything as stunning as an HST image, there’s something even more wonderful about seeing these objects in real time, for yourself, not mediated via a computer screen.

1. Saturn

Hubble view of Saturn
Hubble view of Saturn

Rising around 2030 local time at the end of April, and 1800 local time at the end of May, Saturn is visible in the evening skies throughout the Spring and into Summer. At the moment Saturn’s rings are tilted very favourably towards us, presenting a striking view. Through a very small telescope – or binoculars on a tripod – Saturn might appear as nothing more than a oval, or at best a circular disk with handles, but most modest telescope should show the disk of the planet and the rings, and even Saturn’s largest moon, Titan.

2. Sombrero Galaxy, M104

Sombrero Galaxy, M104
Sombrero Galaxy, M104

The stunning Sombrero Galaxy in the constellation Virgo gets to its highest above the horizon around 2330 in late April, and 2130 in late May. It’s one of the brighter galaxies in the sky, and so even a medium sized telescope should show up the dark dust lane obscuring the view of the central bulge of the galaxy. This dust lane is actually a ring that surrounds the galaxy, and is probably where most of the star-forming takes place, as it is composed of atomic hydrogen and dust.

3. Ring Nebula, M57

The Ring Nebula, M57
The Ring Nebula, M57

Located in the constellation of Lyra in the Summer Triangle, the Ring Nebula (Messier number 57) is a striking object in medium or large telescopes. It rises from low in the NE mid evening to almost directly overhead by the time dawn begins to brighten the sky. The Ring Nebula is a great example of a planetary nebula, so-called as it looks like the disk of a planet when seen through modest telescopes. However this name is completely misleading, as the gas in this nebula was puffed off by a red giant star just before it died and collapsed into a white dwarf, a fate that awaits the Sun in 5 billion years or so.

4. The Great Globular Cluster in Hercules, M13

The Great Globular Cluster in Hercules, M13
The Great Globular Cluster in Hercules, M13

This spherical collection of around 300,000 stars is one of the best examples of a globular cluster in the sky. It’s high in the SE sky during the evenings of April and May, and continues to be visible into the Summer. M13 is at the very limit of naked eye visibility, and small telescopes show it off beautifully. In fact, this is one object where a smaller earth-based telescope gives you a better overall view of the object than the mighty HST. Hubble has such a high magnification that its field of view is very small. This is fine when you’re looking for tiny faint galaxies millions of light years away, but a nearby globular cluster presents problems; it’s simply too big to fit into the field of view. Nevertheless, this spectacular HST image shows the heart of M13, and the stunning array of stars that make up this beautiful object.

5. The Eagle Nebula, M16

Pillars of Creation in The Eagle Nebula

OK, OK, so maybe this is more strictly speaking a late summer object, but it is visible pre-dawn in late May, low in the south, in the constellation of Serpens. Despite the unsocial hours it keeps at this time of the year, it still has to be included in any top-5 list of Hubble objects. The iconic “Pillars of Creation” image, taken by HST in 1995, is one of the most widely viewed of all Hubble images. It shows giant pillars of gas within the Eagle Nebula within which new stars are being born. However it’s a pretty tricky nebula to see through a telescope. There’s a star cluster within it that you’ll make out even in light polluted skies but to see it best you’ll need to head to a dark stargazing site and be patient.

For maps and tips about how to find these objects, and hundreds more like them using binoculars or a telescope check out my book, Stargazing for Dummies.

UPDATE: I just realised; there are people alive today with degrees in astrophysics who weren’t yet born when the Hubble Space Telescope was launched in 1990!

New Telescope for Christmas?

December 25, 2012 Leave a comment

Are you lucky enough to have been given a shiny new telescope for Christmas? If so you have joined the ranks of thousands of other stargazers around the world, and you’re no doubt eager to get outside and use your new toy.

But a new telescope can be quite a complicated and daunting piece of hardware, so let’s go through the basics, to help you on your way.

1. Read the instructions!
Like most complicated pieces of equipment your telescope should have a user manual or a set of instructions. If not, try looking online. These instructions will help you assemble your telescope, and become familiar with all of the various parts, including the finder scope, eyepieces, focus mechanism, and motion controls.

2. Align the finder scope in the daytime.
The small telescope that sits on the main tube of your telescope is called the finder scope. You can use this to locate an object in the sky, and if the finder- and main telescopes are aligned (facing in exactly the same direction) then that object will be in the centre of the field of view of your main scope too. Aligning the finder scope is a bit fiddly though, so do it in the daytime before you observe. Point your main telescope at a specific distant object, like a far away tree, or chimney pot, or transmitter mast. (WARNING: don’t point it anywhere near the Sun). Once that object’s in the very centre of your main scope field of view, look through your finder scope. The chances are it’s not in the crosshairs here, so adjust the position of your finder scope until it is. This is usually done using small screws that physically move the finder scope around till it’s aligned with the main scope. Now it’s ready to use tonight.

3. Pick the correct eyepieces.
Your scope probably came with a couple of eyepieces. These should be marked with their focal length, in mm. The higher this number the lower the magnification. So a 25mm eyepiece will provide smaller images than a 10mm eyepiece. But magnification isn’t everything. In most cases you should start with your least powerful eyepiece, which gives you the largest field of view. Once you’ve found your target you can substitute a more powerful eyepiece in, to get a larger image. It’ll be larger, but dimmer. After all you’re spreading the same amount of light over a larger image. You’ll also notice any wobbles in the telescope much more when you’re using a higher power eyepiece. So your low-power eyepiece will give you brighter, clearer images, even if they’re much smaller.

4. Learn how to move around the sky.
All telescopes are different, and the way that you move them from one object to the other varies. In general though they will all have hand-screws that you can tighten and loosen to lock the telescope in position, or to move it. There may also be dials or screws to give fine adjustments to a telescope’s positioning. On the other hand, some telescopes – called dobsonians – are just moved by physically nudging the telescope tube. However yours moves, you’ll be doing this in the dark, so practice, practice, practice until it’s second nature to you. Some motorised telescopes find and track the stars and planets for you, but these are a bit trickier to set up properly, so read the instructions.

5. Choose the right targets.
Don’t go hunting down very faint elusive objects on your first night out; stick to the brighter ones that are easier to find. On Christmas night and for a couple of days after, the Moon and Jupiter are up in the evening. Even a small telescope will give great views of the Moon (although you’ll get a better view when it’s not quite so full, and you can observe the line between light and dark, called the terminator line) and will let you see Jupiter’s moons, looking like four tiny specks next to the bright planet Jupiter.

Whatever you look at with your new telescope, enjoy it, and remember that patience is a virtue. You’re the proud owner of a great stargazing tool, but you need to practice to get the hang of using it properly.

Let everyone know what you’ve been observing, and how you’ve found your new telescope, in the comments below.

The Galileoscope

I just finished building my first Galileoscope!

The Galileoscope

The Galileoscope

This is an excellent little kit telescope developed during the International Year of Astronomy 2009, and it’s intended to be used as an educational resource.

You can put it together and take it apart as often as you like – you don’t need glue to assemble it – and in its half-constructed form it can be used as an optical bench to test the optics.

I haven’t observed with it yet, but by all accounts it’s very  good. Especially given that the objective lens is made of glass rather than plastic, which reduces aberation, and the eyepiece lens system is composed of two plastic acromatic doublets.

I’ll take it out next time it’s clear and have a look at the Moon and whatever else is up!

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