Vixen Flip Mirror

I wrote a few weeks ago I had bought a Skywatcher ED80 Refractor and I’m very pleased with it (in spite of the excess of grey cloudy skies, we seem to have had recently!).

Well.. I’ve just added a great accessory to the refractor..

It’s a Vixen Flip Mirror.  

And I’m also very pleased to have come across this well-made gadget, because it’s already making my observing so much better.

The flip mirror allows you to have two devices attached to the telescope and flip between them, simply by turning the knob you can see in the image to the right.

In this way, you can be using say, two 1.25″ eyepieces of different focal lengths, at the same time.

Use a low-power to find the object, then flip to a higher-power to observe.  Or, you could have one eyepiece for alignment and one camera for imaging.

Whatever the combination, you can quickly alternate between the two ports, according to your needs.  Much better than trying to swap eyepieces or cameras, in the dark!

One eyepiece tube unscrewed to reveal t-thread

Lots of uses…

And as well as this flexibility to have two devices attached to the telescope, the flip mirror has also solved two other problems I was having..

Problem 1 Solved! As I mentioned in the previous post, the telescope needs some form of extension tube to bring an eyepiece to focus. Previously, I was using a separate extender tube.  Now, the flip mirror provides the extra length of light path and does the job.

Problem 2 Solved! Using the right-angle port, makes it comfortable to view objects high up in the sky, without needing an excessively tall tripod or other support.

Vixen Flip Mirror attached to ED80 Skywatcher

Here’s a picture of the Vixen flip mirror attached to my 80ED refractor.
It’s going to prove a very good buy, I think.  I paid £53 (about $80).
The picture shows it with two 1.25″ eyepieces attached.

Just announced, the Society For Popular Astronomy has up to 1000 telescopes to give to qualifying UK schools, as part of their IYA2009 International Year of Astronomy celebrations.

The telescopes are 70mm, 700mm focal length (F10) refractors on easy-to-use, alt-azimuth mounts. They have been carefully selected for their decent optical quality and versatility, while being suitable for general school astronomy lessons.

What Could You See?

One of these telescopes should give great views of the Moon, with plenty of crater detail to study, plus exciting sights of the largest planets in our Solar System, Jupiter and Saturn.  

The rings of Saturn and the belts of Jupiter’s surface, should be within reach on a clear night.

Even from our light-polluted cities, these telescopes will reveal star patterns, which can’t be seen with the naked eye. And in good seeing conditions, you may be able to see nebulae and even other galaxies, outside our own Milky Way.

How To Apply

There is a simple application process.  Basically, any UK secondary school can write up to 500 words, saying what lessons the telescope would be used for, to be in with a chance of getting one.

The details and application form can be downloaded from the SPA Telescopes For Schools page. 

To help teachers, they will also get a DVD showing how to set up the telescope and suggesting how it might be used in lessons.  There will also be website pages, providing astronomy teaching ideas and assistance.

All applications from schools need to be received by 31 December 2008.

So, if you are a teacher, parent or student and think your school could make use of a telescope, download the application form now.

My new telescope was delivered two days ago, so here are the first impressions.

It’s a Skywatcher 80ED refractor from the Evostar Pro series. This means it has an 80mm diameter, high quality objective lens, made from fluorite glass.

This special glass material is used to eliminate false color as much as possible from observations and keep them sharp.

ED1 OTA Version (optical tube assembly only)

It’s the first high-quality (apochromatic) refractor I’ve owned. Before purchase, I asked experienced astronomers and this telescope was well-recommended for it’s image quality and value for money.

Skywatcher 80ED showing necessary extension tube

I bought the ED1 version – this is the bare optical tube (OTA) only. You can also get the ED2 version. It’s exactly the same optical tube, but comes also with 2 eyepieces, finderscope, diagonal and case.

I already had eyepieces so I decided to save money and just get the OTA, which cost £235 (about $420) delivered.

Attaching To A Mount

First impressions were good.

The tube assembly is a handy size and weight. And with a focal length of 600mm (f7.5), it’s fairly short.

It was easy to attach to the equatorial mount, I already had.

You can see from the photo, I have used the white Skywatcher tube rings it was supplied with, but have attached them to the existing bar on the mount.

Because of this, the rings are rather too close together.

I have retained the Skywatcher supplied (longer) dovetail bar and will use it on the next mount. (I intend to get a much better quality, motorised polar mount for this telescope, in the next few weeks)

First Light Through The Scope

Observing Chair and Skywatcher 80ED

Amazingly, the sky was very clear on the first night, so I did some observing.

First thing to point out, is the focus tube is too short to allow use of an eyepiece, ‘as is’.

You need either an extension tube or a star diagonal, to lengthen the optical path and bring the image to focus.

Remember I mentioned above, the ED2 version comes with a 90 degree diagonal attachement.

I used an extension tube I already had. I have annotated the photo above, to highlight this extension.

Observation

Jupiter is bright, but rather low in the South at present. It made a good first target for the new refractor.

I was very pleased to get a good sharp image of Jupiter, using a 9mm eyepiece. I could clearly see the darker bands on the planet.

The crayford focuser of the scope is very smooth and nice to use.

I really needed higher magnification, but the 9mm eyepiece is the shortest focal length I have at present. With the 600mm focal length of the telescope, it gives only 66 times magnification. (600 divided by 9)

I’m confident I will see clear views at much higher power, so I am well pleased with the new refractor.

I will report progress over the next few weeks.

Generally, this is a very good thing. You can now buy a very capable, powerful instrument for a remarkable price.

It is not unusual for amateurs to obtain a 6 inch, 8 inch, or even 10 inch aperture telescope, quite possibly as their first serious instrument for astronomy. And, built-in computerised control is becoming common.

As I say, this is good.

However, I think a few words on the real-world practicalities of using these telescopes, may be helpful to beginners, before they part with their money.

I am certainly not trying to put you off buying a decent sized telescope. I encourage you to do so, assuming you are interested in astronomy and can afford it.

Just think through these practical aspects in advance and it will be all the more enjoyable.

Storing The Telescope

Telescopes are large items and they have an awkward shape. They take up quite a lot of space in a small house, even if they can be partly dismantled, say by removing the tripod.

They need to be protected when not in use, from dust, moisture, excessive heat and cold, being knocked over and inquisitive children who want to take them to pieces.

Consequently, you need a large cupboard or a corner of a special room, that can be set aside to store your telescope.

Assembling The Telescope And Moving It Outside

Telescopes are heavy, particularly if they are larger than 6 inch aperture.

Also, you may have to do some limited reassembly, like putting it back onto the tripod, before it is ready for use.

At 8 inch aperture and above, moving the telescope safely is really a two-person job. Think about this before you spend thousands on a large telescope

Firm Mounting

To get good results, you need a flat, solid area to site the telescope. When you use even moderate magnification, any movement in the floor surface will drive you mad, as you try to track faint objects.

A wobbly wooden deck is not much good.

Concrete is firm, but if it has been heated by the Sun, it generates thermal air currents moving upwards past the telescope. This spoils the image.

Grass, providing it is dry and firm, is surprisingly good as a base for your telescope, as thermal effects are limited.

Cooling Down Time

A refractor or schmidt cassegrain telescope is sealed and so it does not need very long to aclimatise to the outside temperature.

A reflector is very different, however.

Don’t think you can take one out of a warm room and put it outside where the temperature is 20 degrees lower, and then immediately see good images.

A reflector takes up to two hours to settle to thermal equilibrium with the outside temperature. Only then will it provide good images.

As any telescope cools, dew starts to form on the lenses and mirrors. This is frustrating. A dew shield can help, but some people experiment with mild electrical heating to dispel the moisture.

Aligning The Telescope

“Go-To” computer controlled telescopes are very tempting, especially for beginners who do not know their way about the night sky and generally, they are very good.

This type of telescope is common now. It has a computer that will automatically point the telescope at the celestial object you want to observe. Telescope dealers use this as a BIG selling point.

However, the Go To system will find nothing unless the telescope has been accurately aligned.

This involves entering certain settings for latitude, date and local time into the computer and then going through an alignment process, usually involving the finding of two bright stars.

In my experience, many people find this alignment process difficult and time-consuming.

It can totally spoil the idea of “just popping outside with the telescope” to observe something.

So please bear in mind, that Go-To controllers need proper setting up, if they are to work as promised.

If you find it difficult to use a computer, say to find and use websites on the internet, you will find it tricky to use a computerised telescope Go-To system properly.

Summary

None of these points are meant in any way to put you off buying a good telescope. Modern commercially produced telescopes offer fantastic value for money, compared to what used to be available.

I suggest only that you give these practical considerations some thought before you purchase. Then your new telescope should give you the rewarding experience, it is surely capable of delivering.

In mythology, Orion is said to be a hunter. The shape of the stars in the sky can be interpreted as a man, with a belt and sword, who is holding out a shield against the neighbouring constellation of Taurus, the Bull.

Constellation of Orion

However, from northerly latitudes in Summer, Orion is below the horizon at night and cannot be seen.

The main and easily recognised star pattern within Orion, is four stars in a rectangle which is bisected by the slanted “belt” of three stars.

In one direction, the belt points to Sirius, which is the brighest star in the sky and in the constellation of Canis Major. In the other direction, the belt points to the orange-red star Aldebaran in Taurus.

Orion is therefore a very useful “signpost” in the sky.

The “sword” of Orion, which appears to hang down from the belt, is actually a huge nebula (M42/M43), where stars are being created.

Each of the four main stars are bright and interesting.

Betelgeuse

The top left star (for an observer in the northern hemisphere) is the brightest. It is alpha-Orionis, called Betelgeuse.

Betelgeuse is noticably red-coloured to the unaided eye and is a red super-giant, variable star.

Its magnitude fluctuates between O and 1.3 every 6 years and it also pulsates in diameter from 300-400 times the size of the Sun. It is a true giant and it is 430 light years away.

Rigel

The bottom right star is Rigel and it is usually the brightest in Orion at magnitude 0.2. However, because of Betelgeuse’s variability, Rigel is designated beta-Orionis (not alpha-Orionis).

Rigel is a blue-white supergiant that is 800 light years away so it is nearly twice as far from Earth as Betelgeuse.

Bellatrix

The star at the top right (for Northern hemisphere observers) is a gamma-Orionis, called Bellatrix. It is a blue giant of magnitude 1.6

Saiph

The bottom-left star is Saiph, kappa-Orionis, at magnitude 2

The “Belt” of Orion

In some ways, the three stars which form the “belt” are the most interesting.

From left to right, they are zeta-Orionis called Alnitak (“the girdle”), then epsilon-Orionis called Alnilam (“string of pearls”), and lastly delta-Orionis called Mintaka (“belt”).

Alnilam is a blue super-giant, magnitude 1.7. It is 1600 light years away.

Both Mintaka and Alnitak are multiple stars.

Mintaka is an eclipsing binary with a period of 6 days. The pair is a magnitude 2.2-2.35 blue-white star with a magnitude 6 companion you can see in binoculars and small telescopes.

Alnitak is a tight pair of stars with magnitude 1.8 and 4. You need a good telescope to split them.

Sigma-Orionis

Just below Alnitak, is another multiple star, sigma-Orionis. It looks like a double star in binoculars, but a decent small telescope will actually show it to be four stars.

The “Sword”

As mentioned above, the Sword can be seen just under the belt.

It is a swirling mass of gas called the Orion Nebula, where stars are being born and it is excellent to observe through binoculars or telescope.

When Messier compiled his famous catalogue, he recorded this gas cloud as two separate objects, M42 and M43. Astronomers now believe them both to be part of the same cloud, although there is a dark area which makes them look separate, through a small telescope.

The “Trapezium”

In the centre of the Orion Nebula is the multiple star, theta-Orionis. Through a telescope, you can see a trapezium pattern of four stars.

It is believed that these stars have actually been created from the cloud of gas that is the Orion Nebula and that it is their light, that makes the Nebula glow.

Summary

As you can hopefully appreciate and see, the constellation of Orion is fascinating and well-worth some of your observing time, with binoculars or telescope.

It is known as “the Swan” because of its distinctive cross-shape in the sky. You can imagine it as a flying swan, with wings outstretched.

Cygnus has a declination of 29 degrees so it can be seen high in the sky to the south during the summer, from northerly latitudes. It is also visible to southern hemisphere observers.

Deneb

The brightest star, alpha-Cygni, is called Deneb (“the tail” from the Arabic).

Deneb is one of the brightest stars in our sky, having a magnitude of 1.2, in spite of it being 2000 light years away. Its absolute (or actual) magnitude is -7, which means it is 30,000 times brighter than our Sun.

Deneb is the most distant, first magnitude star.

Albireo

The double star Albireo (beta-Cygni), marks the head of the swan and it is a showpiece of the sky.

Look at it through a small telescope and you will see a pair of stars in contrasting colours. There is an amber star of magnitude 3, together with a blue-green star of magnitude 5. Beautiful!

The Milky Way

Cygnus lies in a particularly rich area of the sky for stars and clusters because we are looking here, into our own galaxy, the Milky Way.

On a dark and clear night, you can see with the unaided eye a “gap” in the Milky Way, to the side of Cygnus, called the “Cygnus Rift” or “Northern Coalsack”. It is not in fact a gap in the stars, but actually a dark area of dust produced by stellar explosions, that obscures our view of stars in this area.

Veil Nebula

Below the left arm (for northern observers) is an area of gas called the Veil Nebula. This is the remains of a supernova, or exploding star, from 30,000 years ago.

It is tricky to see without imaging the area, although you can see it under good conditions using a low-power telescope.

61-Cygni

This is a pair of orange dwarf stars, that are some of the closest stars to us (just 11 light years away). A good target for a small telescope.

The Coathanger

Below Albireo, towards the constellation of Aquila, is another good target for binoculars and small telescopes. It is not technically in Cygnus, but in the constellation of Vulpecula.

The Coathanger is a cluster of stars and the brightest ones, look just like an inverted coathanger.

Summary

For observers in the Northern hemisphere, the constellation of Cygnus make an interesting observation area. It is high in the sky, so you can see nice sights, even if the sky is not particularly dark.

He was initially a successful musician, but then began to concentrate on his hobby of astronomy.

Over the course of the next fifty years, he become the greatest telescope-maker of his time and quite possibly, the greatest observer ever.

The big achievement he is now most often remembered for, is his discovery of the planet Uranus in 1781.

He did this with his home-made telescope. It was the first ever planet discovered by telescope…

William Herschel said of himself, “I have looked further into space than any human being did before me”.

He also encouraged his sister Caroline Herschel and his son John Herschel, to become successful astronomers.

William Herschel was originally from Hanover in Germany, the son of a musician.

Born in 1738, he found himself in 1757, in the army and fighting the French, after they had invaded Hanover.

He deserted and escaped to England.

He began to work as a musician and in 1766, was appointed to a prestigious position as organist at the Octagon Chapel at Bath.

At this time, Bath was a very fashionable resort for high society. William’s Hanoverian origins were probably an advantage, with George the third as King.

His sister Caroline joined him as housekeeper and assistant in 1772 and it was from his house in King Street, Bath that he began to practise astronomy.

He began to make his own telescopes, being dissatisfied by those that were available at the time.

Herschel made reflecting telescopes, using a mirror to gather light, instead of the more usual lens. He made his own mirrors from a very hard alloy of copper and tin called “speculum”. He somehow worked out a way of polishing the hard surface into a reflecting surface of the correct profile to give a good image.

Two things resulted from the telescope making expertise he had developed. Firstly, Herschel was able to observe and map the sky in unprecendented detail. Secondly, his telescopes became sought after and Herschel went on to make a lot of money from the building of telescopes.

Caroline played an important part in this work. She was closely involved in the telescope making and also the observation work.

His big breakthrough came in 1781 when he discovered Uranus. He became famous and was summoned to visit King George III, to demonstrate his telescope and explain the discovery.

As a result, the King appointed Herschel as his own astronomer, with a salary for himself and his sister Caroline, plus a house at Slough (near Windsor) which was to be set up as an observatory.

He also pardoned him for desertion from the army.

There at Slough, William built his largest telescope which had a 48 inch mirror and a focal length of 40 feet.

For more than thirty years, the Herschels continued with their meticulous work on the night sky.

They sent countless papers to the Royal Society, cataloguing and describing the objects they had observed.

In recent years however, various hybrid types have become available, which attempt to combine the best features of the two traditional types. But we will discuss more about hybrid designs in a moment.

Refracting telescopes use a main lens made from glass and called the objective lens. This lens bends (or refracts) the incoming rays of light as they pass through it, so they come to a focus. This was the type of telescope that Gallileo famously used back in the early 1600′s to make the first astronomical observations of the Moon and Jupiter.

Reflecting telescopes on the other hand, do not use an objective lens, instead they use a main or primary mirror. The surface of this mirror is specially shaped into a concave curve called a parabola, which has the handy property of reflecting all incoming light rays to a focus.

Let’s look at these two traditional types in more detail.

Refractors

Refracting astronomy telescopes have a main lens ranging in size from about 60mm (2.5″) in diameter and then on upwards. The cost increases quickly, as it is expensive to make good quality lenses, so it is rare to see an amateur instrument with a size greater that 150mm (6″).

Refractors have the advantage of allowing all the light collected by the objective lens, to pass unobstructed through the telescope to the eyepiece at the other end of the tube. Consequently, even small diameter instruments can work well. A decent quality 70-80mm refractor is still an excellent telescope for amateur use.

The problem with refractors however, is so-called chromatic abberation. This simply means that false colour can be introduced to the image you are observing. This happens because the different colours of light within white light, are bent by the lens through slightly different angles, resulting in slightly different focal points.

This used to be a big problem until it was discovered that by sandwiching two (and more recently three) lenses into a doublet or triplet lens, and also by using special glass, these false colour effects in the image could be removed.

Refractor telescopes with colour correction are called achromatic and the best ones, using the multi-element lenses are called apochromatic.

However, the manufacture of these clever lenses is expensive, although the prices of achromatic refractors has come down greatly in the last few years because of Far Eastern factory production.

Reflectors

The reflecting telescope was invented by Sir Isaac Newton in the early 1700′s. As we have said, it uses a mirror to focus incoming light.

This has two big advantages – firstly mirrors are cheaper to make than lenses and you can make them in large sizes, and secondly, mirrors do not have the problem of false colour.

As a result, you can get a much bigger reflector for your money and they have always been very popular amongst astronomers. The largest telescopes in the World all use mirrors.

The disadvantage however, is that you need a bigger reflector to get the same light-gathering power as a refractor because it is necessary to use a second mirror (the secondary) to divert the focussed light beam into the eyepiece. This second mirror within the telescope tube, blocks out some of the light.

Hybrid Telescope Designs

Recently, we have seen the emergence of hybrid designs which combine mirrors and lenses. These catadioptric reflectors are compact telescopes that are capable of producing high quality images, while being available at reasonable cost (typically a few hundred £ or $).

These hybrid telescopes use a lens called a corrector plate at the top of the tube, together with a primary mirror at the bottom. Mounted inside the tube is a secondary mirror. This reflects the light a second time back down the tube and out through a central hole in the primary mirror, and into the eyepiece (or other imaging device).

There are a few disadvantages, but they usually work very well and have consequently become very popular amongst amateur astronomers.