When considering the purchase of a refractor it helps to know a little about the various telescope types and the benefits and drawbacks each type has. A refractor collects light using a lens like a large magnifying glass. The chief benefit of a refractor is high contrast views that reveal more detail of celestial objects to the observer. A reflector uses two mirrors to collect light. Its secondary mirror can reduce contrast and obscure fine detail. The refractor’s chief detriment is a phenomenon known as “chromatic aberration.” Since different wavelengths of light reach best focus at different points in the refractor’s optical tube a blue-violet fringe appears along the edge of very bright objects such as the Moon and Jupiter. Correcting chromatic aberration is not too difficult….. as long as you have a generous budget. A refractor that is virtually colorfree known as an “apochromat” can cost upwards of a thousand dollars or more per inch of aperture because of the addition of an element to the lens made of fluorite or other rare earth glass that increases the complexity of the manufacturing process. An “achromat” is a refractor that lacks the extra “apo” lens element. It would be great if we could all afford one but if you’re in the market for a refractor that delivers excellent performance at a price that won’t bankrupt you Astrozap’s premium achromatic refractors can’t be beat. Astrozap’s achromatic refractors are designed built and priced to deliver nearly color-free performance at an affordable price. These telescopes come in 5 and 6 inch apertures and in two optical models.The Astrozap Widefield Petzval Refractor utilizes an optical system named for its inventor Joseph Petzval who introduced this type in 1856. The Petzval configuration pairs an f/10 air spaced well corrected doublet (two element) objective with a matched second reducing / correcting lens group positioned just ahead of the focuser draw tube. This combination yields an f/5 optical system with a flatter field and less color than any standard achromat of the same diameter. This telescope type is well suited to sweeping views of the heavens and is particularly useful for exploring larger deep sky objects and panoramic vistas.
