ISTAR Optical

Why choose a refractor?

Ask anybody to describe a telescope and the image of a long tube and lens at the end will be their answer. Except for the diagonal, which makes possible viewing at a comfortable angle, there are no mirrors to scatter and lose light. There is no central obstruction, no frequent collimation to worry about and very reasonable cool down time. How about sharp, high contrast views of the Moon and planets? If you like black velvety backgrounds with pin point stars, a refractor is for you.

Why a long focal length?

Using long focal lengths puts large aperture refractors within reach of most amateurs. Most people associate inexpensive achromatic lenses with horrendous amounts of false color (chromatic aberration). Not so with longer focal lengths. When the focal length is increased in relation to the aperture the inherent aberrations associated with achromats are minimized. Another advantage is depth of focus. No constantly tweaking the focus. Greater depth of focus allows a steady, comfortable viewing experience especially when observing the Moon, planets and double stars.

What is a Bare OTA?

Istar does not offer mass produced telescopes with non-replaceable focusers, low quality rings and dovetails. Instead, we offer you the option to purchase a bare OTA with optics and give you a choice of focusers, mounting rings and dovetail. You do not have to purchase these from Istar. You are welcome to buy from third party manufacturers. However, we offer the original Istar PRO style rings and dovetails that are of the highest quality, stability and match each scope perfectly.

What is an R30 or R60 doublet?

Istar uses special exotic glass types to achieve 30 to 60 percent reduction in CA and spot size compared to a common doublet made with popular less expensive glass types.

Istar Lens Caps

We ship all scopes with a specially designed lens cap. You can decrease or increase friction inside of the dew shield by loosening or tightening the two silver bolts. When you tighten them the diameter of the foam ring will increase therefore increasing the friction inside the dew shield. They look unlike any other lens cap on the market and of course and they work better than any other lens cap.

Why are Istar scopes black?

Our scopes are built around a “color scheme” which is not just aesthetically attractive but highly functional. Achromats are black matte with a polished silver counter cell and silver back plate. Apochromats are black matte with a red-gold counter cell and red-gold back plate. Add a set of black CNC machined rings, black focuser and black Istar diagonal with polished silver body plate and you have a beautiful instrument. The textured finish is not only durable but gives a sure grip when handling the tube. Black does not require any longer cool down time than the popular white tube. However, if you do not like black, white is available for a small additional charge.

How can I fix a scratch on my Istar scope tube?

Istar tubes are powder coated. However, a “quality” black matte spray paint can be used to cover a scratch. The paint sprayed over top of the powder coat will take on the texture of the original finish. Use only as much paint as is necessary to cover the scratch. After drying the paint should have blended well.

Concerning the R30 and R65 products. What is the actual effect of a 35% or 65% reduction in CA?

Generally the effect of a 35% or 65% reduction in CA is smaller SPOT size. For example, the R65 lens should have about the same amount of false color as a scope with a 65% longer focal length, or about the same as an F/8.25.

Why is the price on the Istar Optical Web site less than my US dealer?

Scopes ordered directly from Istar are at present shipped from the Czech Republic in Europe and do not have DHL shipping charges or import taxes added.

Are ISTAR telescopes produced in China?

Absolutely not! Istar’s mechanical and optical designs are created in the Czech Republic, Europe. All of our lenses were designed by Master Optician Zdenek. The telescopes and related parts were designed by the owner of Istar, Ales Krivanek. Telescope tubes and dew shields are produced in Austria and CNC machined and powder coated in the Czech Republic. Scopes are assembled by hand and tested in the Czech Republic and the United States. Currently all materials used are of European origin with the exception of focusers that are made in the US. A major expansion will take place in 2012 with most manufacturing and assembly being moved to the United States. Lenses are ground and polished in Asia to Istar’s exact quality specifications and exported to the US to be mounted and shipped worldwide. Only brand name glass from O’Hara, Schott and CDGM is used.

Is the ISTAR Perseus line of achromatic doublets suitable for astro-photography?

Yes. Istar lenses are made to meet high quality standards. Many knowledgeable and experienced astronomers have made it clear that even though these instruments have only a modified Fraunhofer (air spaced achromatic doublet) in them, they are suitable for a good quality Moon, planetary and DSO photography. Incredible results with pinpoint starts and vivid colors have been achieved with use of a narrowband filter.

Is the ISTAR Phantom line of telescopes made with CaF2 or simple Fluorite glass?

There are many manufacturers offering so called Fluoro-Star, Fluoro-Triplet and Fluorite Triplet Glass to make buyers believe their instrument is made with a pure fluorite element. Calcium Fluorite is the best optical material on the market today in terms of color correction. It is also the most expensive. All Phantom CFT telescopes are made with pure crystallized Calcium Fluorite, CaF2. There are very few manufacturers that produce scopes made with this rare material. Images taken with CaF2 triplets are in class by themselves and are rightfully considered to be the very best among knowledgeable astro photographers. Have you viewed a DSO or planetary image taken with a Phantom CFT scope? If you did, you are probably saving your money to purchase one.