Vixen A70lf Refractor Telescope

This Little vixen refractor, with only a 70 mm aperture offers sharp planetary views and is especially cheap and £69 for the optical tube assembly. We bought it to demonstrate how small, cheap telescope can perform against larger aperture telescope's. Generally speaking, small factors. Even long ones like this can be used quite easily, and require hardly any maintenance. At this price point, they also make excellent guide scopes with astrophotography.

Refractors (also known as dioptrics) are what the average person identifies with the word "telescope", a long, thin tube where light passes in a straight line from the front objective lens directly to the eyepiece at the opposite end of the tube. Lately those focal lengths have got shorter as astrophotography matures and gets cheaper with the advent of Digital SLR Cameras with better low light performance.

Advantages

• Easy to use and reliable due to the simplicity of design.
• Little or no maintenance.
• Excellent for lunar, planetary and binary star observing especially in larger apertures.
• Good for distant terrestrial viewing.
• High contract images with no secondary mirror or diagonal obstruction.
• Colour correction is good in achromatic designs and excellent in apochromatic and fluorite designs.
• Sealed optical tube reduces imagine degrading air currents and protects optics.
• Objective lens is permanently mounted and aligned.

Disadvantages

• More expensive per inch of aperture than Newtonians or catadioptrics.
• Heavier, longer and bulkier than equivalent aperture Newtonians and catadioptrics.
• The cost and bulk factors limit the practical useful maximum size objective to small apertures.
• Less suited for viewing small and faint deep sky objects such as distant galaxies and nebulae because of practical aperture limitations.
• Focal ratios are usually long (f/11 or slower) making photography of deep sky objects more difficult. f/4 to f/7 are preferred for this.
• Some Colour aberration in achromatic designs (doublet). Apochromatic Refractors are pretty much colour free, but this is reflected in the cost.
• Poor reputation due to low quality imported toy telescopes; a reputation unjustified when dealing with a quality refractor from a reputable manufacturer.

In summary a small reflector is the best general purpose telescope for beginners as they are good on all types of objects and for starting astrophotography, if they are lower than f/10 focal ratio, f/5 being very fast. 90mm f/6 is an ideal portable telescope.

If you wish for the ultimate planetary telescope, and also a scope which is virtually maintenance free then look no further than a refractor.