Galloway Astronomy Centre SCOPE SHOP
Tel: 01988 500594
The Basics Telescopes There are thee main types of telescope - Refractor, Reflector and Catadioptric Refractor - telescope has two or more lens at the front. Minimum lens diameter recommended is  80mm. This type of telescope is good for viewing the Moon and planets, but limited to brighter  Deep Sky Objects (DSOs) ie Galaxies and nebulae, except for larger aperture ones, but these are  expensive and heavy. Short focal lengths (400 or 500mm) give a wide field of view so the planets will look quite small.   For a decent view of planets a focal length of 900mm or more is recommended.  Reflector - telescope uses mirrors. Minimum mirror diameter recommended is 130mm. The smaller  aperture telescope is good for viewing the Moon and planets, but limited to brighter DSOs. A  150mm telescope will give much brighter images allowing fainter objects to be seen more easily.  Larger apertures of 200mm or more are more expensive and can be cumbersome, but will give  unrivalled views of fainter DSOs.  Short focal lengths (700mm or less) give a wide field of view so again objects will look small.  Longer focal lengths of over 1000mm allow objects to be made much larger.  Catadioptric - telescope uses both a glass “corrector” plate and mirror. Even small ones are  expensive compared to the other two types due to the complexity of design. For apertures of  105mm or more they offer good views of the Moon, Planets and brighter DSOs equal to high quality  refractors for a similar aperture, but at a lower price. Mounts All telescopes need a mount to allow it to be pointed at the sky accurately and firmly. An Equatorial mount is complex and, therefore, expensive. It allows the telescope to be moved in  only one axis to track the motion of the stars, etc. The mount can be fitted with motor drives to  automatically follow the sky. This type of mount is used for all three types of telescope. A Dobsonian mount is simple, sturdy Alt Az (Altitude and Azimuth) mount constructed like a wooden  box which makes it relatively cheap. It is only sold with reflector telescopes. The telescope can be  moved left and right, up or down easily. Their advantage is that most of your money goes into the  optics. The only drawback is that the telescope needs to be moved a little bit on two axis when  viewing an object (an easily mastered technique) otherwise it will move out of the field of view due  to the Earth's rotation. Motorised versions are available but add to the price. Alt Az (Altitude and Azimuth) mounts has recently seen a revolution with the introduction of the  single arm motorised mounts. This light weight, strong, stable mount is designed for small refractors  and reflectors. Also see GOTO Mounts in Finally Note: Large catadioptric telescopes are often sold on sophisticated heavy weight single arm and  forked Alt Az mounts.  Finder Typically, smaller telescope come with a red dot finder (RDF), while suitable for locating bright  objects like stars and planets they can be difficult to use when finding DSOs. Larger telescopes are fitted with a magnifying finder (effectively a mini telescope), typical sizes are  6x30 (6 times magnification with 30mm aperture) and 9x50.  Note – cheap, poor quality telescopes are often fitted with a tiny 20mm finderscope which is  virtually useless - avoid telescopes supplied with these or at the least replace it. Eyepieces Most telescopes come with one or more "Plossl" eyepieces (EP). The focal length (FL) of the EP  appears as a number on the barrel. By dividing the FL of the telescope by the FL of the EP the result is the magnification with that EP. E.g.  1000 / 25 =  40x magnification.   You can reverse the calculation to determine the eyepiece FL to achieve a specific magnification. Typically only 3 EPs are needed to give a range of magnifications between 30x to 100x and if a 2x  Barlow is used as well this will double these magnifications. There is little point exceeding 160x with  telescopes under 150mm as the image becomes too dim.  You can work out a rough maximum magnification for any telescope by multiplying its aperture (in  inches) by 35. Many telescopes are fitted with a focuser capable of taking both 1.25" and 2" EPs (although  Skywatcher only include 1.25" EPs). This size is the diameter of the EP barrel. 2" EPs are physically  larger, more expensive and offer wide-angle views.  One note of caution – Ultra Wide-angle EPs, both 1.25" and 2", have become very common. While  they work well with the long FL Refractors and Catadioptric telescopes, these EPs should be avoided  for the shorter FL refractors and reflectors. There is a huge range of eyepieces on the market, again we can offer advice on what best suits each type of telescope. Next - And Finally 
Equatorial Mount 
Dobsonian Mount
Alt AZ Mount 
6x30 Finderscope
Red Dot Finder
© Galloway Astronomy Centre 2016          All images are copyright – M Alexander unless otherwise stated
Scopes Introduction Basics Finally Scope Mods Skywatcher Celestron Optical Hardware Basics
Galloway Astronomy Centre SCOPE SHOP
Tel: 01988 500594
© Galloway Astronomy Centre 2016 All images are copyright – M Alexander unless otherwise stated
The Basics Telescopes There are thee main types of telescope - Refractor, Reflector and  Catadioptric Refractor - telescope has two or more lens at the front. Minimum lens  diameter recommended is 80mm. This type of telescope is good for  viewing the Moon and planets, but limited to brighter Deep Sky Objects  (DSOs) ie Galaxies and nebulae, except for larger aperture ones, but  these are expensive and heavy. Short focal lengths (400 or 500mm) give a wide field of view so the  planets will look quite small.   For a decent view of planets a focal length of 900mm or more is  recommended.  Reflector - telescope uses mirrors. Minimum mirror diameter  recommended is 130mm. The smaller aperture telescope is good for  viewing the Moon and planets, but limited to brighter DSOs. A 150mm  telescope will give much brighter images allowing fainter objects to be  seen more easily. Larger apertures of 200mm or more are more  expensive and can be cumbersome, but will give unrivalled views of  fainter DSOs.  Short focal lengths (700mm or less) give a wide field of view so again  objects will look small. Longer focal lengths of over 1000mm allow  objects to be made much larger. Catadioptric - telescope uses both a glass “corrector” plate and mirror.  Even small ones are expensive compared to the other two types due to  the complexity of design. For apertures of 105mm or more they offer  good views of the Moon, Planets and brighter DSOs equal to high quality  refractors for a similar aperture, but at a lower price. Mounts All telescopes need a mount to allow it to be pointed at the sky accurately and firmly.  An Equatorial mount is complex and, therefore, expensive. It allows the  telescope to be moved in only one axis to track the motion of the stars,  etc. The mount can be fitted with motor drives to automatically follow the sky. This type of mount is used for all three types of telescope. A Dobsonian mount is simple, sturdy Alt Az (Altitude and Azimuth) mount  constructed like a wooden box which makes it relatively cheap. It is only  sold with reflector telescopes. The telescope can be moved left and right, up or down easily. Their advantage is that most of your money goes into  the optics. The only drawback is that the telescope needs to be moved a  little bit on two axis when viewing an object (an easily mastered  technique) otherwise it will move out of the field of view due to the  Earth's rotation. Motorised versions are available but add to the price. Alt Az (Altitude and Azimuth) mounts has recently seen a revolution with  the introduction of the single arm motorised mounts. This light weight,  strong, stable mount is designed for small refractors and reflectors. Also  see GOTO Mounts in Finally Note: Large catadioptric telescopes are often sold on sophisticated heavy weight single arm and forked Alt Az mounts.  Finder Typically, smaller telescope come with a red dot finder (RDF), while  suitable for locating bright objects like stars and planets they can be  difficult to use when finding DSOs.  Larger telescopes are fitted with a magnifying finder (effectively a mini  telescope), typical sizes are 6x30 (6 times magnification with 30mm  aperture) and 9x50.  Note – cheap, poor quality telescopes are often fitted with a tiny 20mm  finderscope which is virtually useless - avoid telescopes supplied with  these or at the least replace it. Eyepieces Most telescopes come with one or more "Plossl" eyepieces (EP). The focal  length (FL) of the EP appears as a number on the barrel. By dividing the  FL of the telescope by the FL of the EP the result is the magnification with that EP. E.g.  1000 / 25 =  40x magnification.   You can reverse the calculation to determine the eyepiece FL to achieve a specific magnification. Typically only 3 EPs are needed to give a range of magnifications between 30x to 100x and if a 2x Barlow is used as well this will double these  magnifications. There is little point exceeding 160x with telescopes under  150mm as the image becomes too dim.  You can work out a rough maximum magnification for any telescope by  multiplying its aperture (in inches) by 35.  Many telescopes are fitted with a focuser capable of taking both 1.25"  and 2" EPs (although Skywatcher only include 1.25" EPs). This size is the  diameter of the EP barrel. 2" EPs are physically larger, more expensive  and offer wide-angle views. One note of caution – Ultra Wide-angle EPs, both 1.25" and 2", have  become very common. While they work well with the long FL Refractors  and Catadioptric telescopes, these EPs should be avoided for the shorter  FL refractors and reflectors. There is a huge range of eyepieces on the market, again we can offer  advice on what best suits each type of telescope. Next - And Finally 
6x30 Finderscope
Red Dot Finder
Equatorial Mount 
Dobsonian Mount
Alt AZ Mount 
Scopes Introduction Basics Finally Scope Mods Skywatcher Celestron Optical Hardware Basics
© Galloway Astronomy Centre 2016 All images are copyright – M Alexander unless otherwise stated
The Basics Telescopes There are thee main types of telescope - Refractor, Reflector and Catadioptric Refractor - telescope has two or more lens at the front. Minimum lens diameter recommended is 80mm. This  type of telescope is good for viewing the Moon and  planets, but limited to brighter Deep Sky Objects  (DSOs) ie Galaxies and nebulae, except for larger  aperture ones, but these are expensive and heavy. Short focal lengths (400 or 500mm) give a wide field of  view so the planets will look quite small.   For a decent view of planets a focal length of 900mm or  more is recommended.  Reflector - telescope uses mirrors. Minimum mirror  diameter recommended is 130mm. The smaller  aperture telescope is good for viewing the Moon and  planets, but limited to brighter DSOs. A 150mm  telescope will give much brighter images allowing  fainter objects to be seen more easily. Larger apertures  of 200mm or more are more expensive and can be  cumbersome, but will give unrivalled views of fainter  DSOs.  Short focal lengths (700mm or less) give a wide field of  view so again objects will look small. Longer focal  lengths of over 1000mm allow objects to be made  much larger.  Catadioptric - telescope uses both a glass “corrector”  plate and mirror. Even small ones are expensive  compared to the other two types due to the complexity  of design. For apertures of 105mm or more they offer  good views of the Moon, Planets and brighter DSOs  equal to high quality refractors for a similar aperture,  but at a lower price. Mounts All telescopes need a mount to allow it to be  pointed at the sky accurately and firmly. An Equatorial mount is complex and, therefore,  expensive. It allows the telescope to be moved in  only one axis to track the motion of the stars, etc. The mount can be fitted with motor drives to  automatically follow the sky. This type of mount is  used for all three types of telescope. A Dobsonian mount is simple, sturdy Alt Az  (Altitude and Azimuth) mount constructed like a  wooden box which makes it relatively cheap. It is  only sold with reflector telescopes. The telescope  can be moved left and right, up or down easily.  Their advantage is that most of your money goes  into the optics. The only drawback is that the  telescope needs to be moved a little bit on two  axis when viewing an object (an easily mastered  technique) otherwise it will move out of the field  of view due to the Earth's rotation. Motorised  versions are available but add to the price. Alt Az (Altitude and Azimuth) mounts has recently  seen a revolution with the introduction of the  single arm motorised mounts. This light weight,  strong, stable mount is designed for small  refractors and reflectors. Also see GOTO Mounts in  Finally Note: Large catadioptric telescopes are often sold  on sophisticated heavy weight single arm and  forked Alt Az mounts.  Finder Typically, smaller telescope come with a red dot  finder (RDF), while suitable for locating bright  objects like stars and planets they can be difficult to use when finding DSOs.  Larger telescopes are fitted with a magnifying  finder (effectively a mini telescope), typical sizes  are 6x30 (6 times magnification with 30mm  aperture) and 9x50.  Note – cheap, poor quality telescopes are often  fitted with a tiny 20mm finderscope which is  virtually useless - avoid telescopes supplied with  these or at the least replace it. Eyepieces Most telescopes come with one or more "Plossl"  eyepieces (EP). The focal length (FL) of the EP  appears as a number on the barrel. By dividing the  FL of the telescope by the FL of the EP the result is the magnification with that EP. E.g.  1000 / 25 =  40x magnification.   You can reverse the calculation to determine the eyepiece FL to  achieve a specific magnification. Typically only 3 EPs are needed to give a range of magnifications  between 30x to 100x and if a 2x Barlow is used as well this will  double these magnifications. There is little point exceeding 160x  with telescopes under 150mm as the image becomes too dim.  You can work out a rough maximum magnification for any  telescope by multiplying its aperture (in inches) by 35.  Many telescopes are fitted with a focuser capable of taking both  1.25" and 2" EPs (although Skywatcher only include 1.25" EPs).  This size is the diameter of the EP barrel. 2" EPs are physically  larger, more expensive and offer wide-angle views.  One note of caution – Ultra Wide-angle EPs, both 1.25" and 2",  have become very common. While they work well with the long  FL Refractors and Catadioptric telescopes, these EPs should be  avoided for the shorter FL refractors and reflectors. There is a huge range of eyepieces on the market, again we can  offer advice on what best suits each type of telescope. Next - And Finally 
6x30 Finderscope
Red Dot Finder
Equatorial Mount 
Dobsonian Mount
Alt AZ Mount 
Galloway Astronomy Centre SCOPE SHOP
Tel: 01988 500594
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