Choosing a telescope

One of the first questions people interested in astronomy often ask is which type of telescope they should buy.  There is no right answer to this question as it all depends on what you want to do with it and if you even need a telescope at all.
This may seem a nonsense answer at first, but different telescope designs are good at different aspects of astronomy and binoculars offer another, cheaper and more mobile method of observing as well.

Binoculars:
Before purchasing a telescope, may amateur astronomers start with Binoculars. 
They’re cheaper, more mobile and offer a window to the skies without the need to understand the ins and out of eyepieces and mount alignment.
Rather than repeating already sound information, here is a guide from Sky And Telescope.com  on purchasing binoculars for astronomy:
http://www.skyandtelescope.com/astronomy-equipment/binoculars-for-astronomy/

Which Telescope? Credit: Meteorwatch.org

Telescopes:
One thing that any amateur astronomer worth their salt will tell you is that you should never waste your money on the types of telescopes you often see in toy shops, budget supermarkets and many high street chain stores.  These telescopes are often of poor quality optical design, and will boast magnifications which are impossible to achieve, merely to impress you with the idea of being able to see deep into space.  They are also normally very expensive for what they are when compared to beginner telescopes from reputable dealers.  You would always be far better with a decent pair of binoculars (something like 10×50 minimum) than with a cheap telescope from your local Aldi store or eBay!

Optus Telescope

Cheap telescopes, like this Optus which I saw on sale last year in Aldi for £60, will give you disappointing views and are likely to dampen your enthusiasm for what is a fascinating hobby.  The main issues with cheap telescopes are that they suffer from false colour, distorted images, poor resolution, flimsy mounts and tripods, and poor quality eyepieces which further deteriorate the views through the telescope. This size of telescope would never fetch 234x magnification.  The most you could hope to achieve on this model would be 152x mag under perfect seeing conditions, which is rare in the UK.  Also, it boasts an EQ-7 mount which does not exist, the EQ-7 was never released but the EQ-8 was and retails around £2600.00!  Suffice to say, there is not a £2000 mount in this £60 box.

We have a range of telescope dealers featured on our links page, but the main brands you need to look for whether buying second-hand or brand new are Meade, Skywatcher, Celestron, Orion, Revelation, and Vixen.  The majority of these manufacturers have an entry level model, perfect for beginners.  They will give pleasing sights with far better quality optics than anything you can buy on your local high street, at affordable prices.

Skywatcher Skyhawk 1145P Newtonian Reflector on an EQ-1 Mount

A perfect beginner scope, such as this Skywatcher Skyhawk 114P Reflector, will allow you to see the rings of Saturn, the cloud bands and Galilean Satellites of Jupiter, the Orion Nebula, the Andromeda Galaxy and beautiful star clusters like the Pleiades.  These retail at approximately £140 including a sturdy equatorial mount and an appropriate range of eyepieces.

Skywatcher Heritage 130P truss-tubed Dobsonian telescope

 

 

 

 

 

Alternatively this Skywatcher Heritage 130 Dobsonian is slightly larger in aperture, so has better light gathering meaning you can look further into space, and is approximately £150 brand new.

 

Types of telescope

There are 3 main designs of telescope:

  • Refractor
  • Reflector
  • Catadioptric

Vixen ED115 Refractor on a Vixen GPD2 Mount

 

Most people think of telescopes as long tubes, where you look through one end and point the other in the direction you want to view (think pirates)

This is a refractor and uses lenses to magnify the image, bringing it to focus at the eyepiece.  

Refractors tend to be smaller in aperture and more expensive and are best used for looking at the Moon and Planets.

 

 

 

How a reflecting telescope works

Reflectors use mirrors instead of lenses, with light bouncing off the primary mirror and reflecting to the secondary mirror, before focusing at the eyepiece.  The main type of reflector is known as a Newtonian with the eyepiece at the other end of the tube to a refractor.  
Dobsonian telescopes are also reflectors, but are on a different type of mount.  
Reflectors come in much larger apertures and are more affordable than refractors of the same aperture and are best used for looking at deep sky objects such as galaxies and nebulae.
SARAS has a range of Newtonian Reflectors, including our new 16″ Meade Lightbridge truss-tube Dobsonian and a 10″ and 12″ custom built Dobsonian.

Celestron Nexstar GPS 8″ SCT

 

Catadioptric telescopes combine mirrors and lenses to magnify the image and focus at the eyepiece.
These telescopes combine the advantages of the other two types.  
They are good all round telescopes, suitable for both deep sky and planetary observing.
 There are Schmidt-Cassegrain (SCT) and Maksutov-Cassegrain models available, among others.  
SARAS has a 12″ Meade LX200 SCT for members’ use.

 


Safety

One thing you must remember is you should NEVER LOOK DIRECTLY AT THE SUN THROUGH YOUR TELESCOPE unless you have a proper solar filter fitted to the end of the telescope.  
You WILL be premanently blinded by the magnified solar rays if you do not follow this advice.
You should also never  leave a telescope in a position where the light from the sun can enter the telescope as the Sun moves throughout the day.  The magnified rays could start a fire due to the concentrated rays (think ants and magnifying glass on an bigger scale)
There are solar filters available on the market, and it is possible to make one at home from special film which blocks out over 99.9% of the light, such as Baader Astrosolar Safety Film.
These white light solar filters allow views of sunspots but show very little other detail. However great care needs to be taken with making your own filter and no other product should be used for this purpose.

SARAS would always recommend using equipment that has been manufactured specifically for the safe viewing of the Sun.  

This is not an area of astronomy that you cannot afford to cut corners with!

Safe Solar Viewing with a filter

Alternatively, you can buy dedicated solar telescopes such as a Coronado PST or a Meade Solarmax.  These range from £400 to several thousand!  They give views of the Sun in Hydrogen Alpha (Hα) narrowband light and show detail such as granulation on the surface, sunspots, and prominences.  SARAS is fortunate to have members who own a range of solar viewing equipment and they take these along to public events throughout the year to allow people to experience the wonder of watching our Sun in action.

Solar Telescopes including PST and a customised William Optics Megrez refractor using a Solarmax filter

If you are still confused by the range of different sizes and styles of telescope, come along to your local astronomical society and ask for advice.  SARAS has been established in the local community for almost 40 years and we have a wealth of information and experience to share with you, regardless of your level of personal experience in the field.  We even have telescopes that our members can loan to enable some hands-on experience using telescopes before you make the decision on what you want to buy.

You may have already bought your telescope, but be struggling to get to grips with using it. 
Telescopes on equatorial mounts require polar alignment to be used correctly and Newtonian Reflectors require collimation (alignment of the mirrors) in order to achieve good images.  
Both of these processes can be tricky at first and can take several attempts to master.  

If you are finding it hard to know what to do with your telescope, feel free to bring it along to one of our monthly meetings and we will take a look at it with you and help you get to grips with the function of your new kit.  

Our monthly meetings are on our Events Calendar.