GardenAstronomy

If cost is a problem and you are not sure if your interest will last then consider the fact that manual scopes are at least £100 - £140 cheaper than computerised GOTO's.  This is roughly the difference in price between a computerised GOTO 130mm reflector and a manual 150mm.  

 

However, for another £30 or so you can add a motor drive system with handset to the manual scope  so that you can track objects in the night sky.  

 

This means that for around £200 you can get a motorised 130mm reflector.   It won't find objects for you but is at leastt £100 cheaper than the same size GOTO telescope.   But there is another option.

 

Dobsonians: These are the same kind of Newtonian reflectors as mentioned above, but with a much simpler mounting system based on the 'lazy susan' principle.  This keeps the cost down and means that you can buy bigger aperture telescopes for your money - a 200mm Dobsonian for roughly the same price as the 150mm ordinary Newtonian.  More important, in terms of light gathering capacity a 200mm is 78% better than a 150mm scope, and 137% better than a 130mm.  So, if the viewing conditions are good,etc., you will be able to start to see many more interesting objects, including those fascinating faint, fuzzy, deep sky objects.  

 

But - there are always buts..

 

How do you find anything? Well, the same way as with the other scopes by using a finderscope. This isn't any more or less of a problem than with other scopes if the finderscope is properly aligned with the main scope.  However, the larger the aperture of the main mirror the smaller the field of view, and most Dobsonians have to be moved manually in order to track an object.  

 

This means that a star centered in the field of view of a 200mm manual Dobsonian scope will disappear completely in a couple of minutes with a 25mm eyepiece, and in less than a minute with a high power 10mm eyepiece.  And where you have light pollution  it can be difficult to use the finderscope to find anything other than the brightest objects .

 

But a very quick look at some differences which affect what you see.

 

Visual Differences: For the same size (aperature) Refractors give a slightly better, sharper image than Reflectors which in turn do slightly better than Catadioptrics.  

 

Why? Refractors don't have the secondary mirror that Reflectors have, whilst most Catadioptrics (SCT's) have a larger second obstruction than Reflectors.  And  the cheaper Refractors may suffer from colour fringing - this is down to simple physics as light of different wave-lengths bend at different angles and only the more expensive lens construction will eliminate that.  

 

How important these are these differences? Well in the end it usually comes down to personal preferences and until you have used them it is difficult to know which will best suit you.   And there are many other factors which will decide your choice.  In particular

 

The Basic Accessories

 

Please note that all prices quoted are approximate, subject to change

and for guidance only

 

Other Telescopes

Skywatcher 8in Dobsonian

Skywatcher 200mm Dobsonian Reflector

red dot finder

Zero Magnification

Red dot Finder

9X50FINDER

9 x 50 Straight Through Finderscope