Fluorite

Calcium fluorite (CaF2) is a naturally occurring crystal. Its very low refractive index makes it the best of materials to use in the manufacture of apochromatic telescopes. Unfortunately, the natural crystal contains many impurities and as a result make it display some properties that make it less attractive for use in telescopes. Now thanks to modern optics, fluorite crystals are grown in an oven and the product is a totally pure mono crystal structure with all the good qualities of the lowest refractive index, but with none of the problems associated with the natural crystal. Now, this crystal can be hard multi-coated for maximum light transmission and durability.

As the diagram shows, the band pass of fluorite of 1000 to over 100.000 angstroms eclipses by many magnitudes that of any optical glass. Additionally, the use of multi-coatings further increases light transmission over any ED glass. This makes any fluorite objective brighter than any comparable glass objective, not to mention the superior band pass. These features make the fluorite objective the premier instrument for photo/visual observations of deep sky objects.

When the fluorite instrument is taken out for an observing session, 30 minutes should be set aside for temperature equalization for maximum performance. When making astrophotos, critical focus should be checked after every photo to insure the best possible results.

When Takahashi first designed the fluorite apochromatic refractor, they realized that the optimum design placed the fluorite element in front. Coating technology of the time did not permit this to be done. Therefore, an alternate but excellent design placed the element in the rear. Now, due to a production and technological breakthrough, fluorite can be hard multi-coated. The new FS series benefits from this by placing the fluorite element in front with low dispersion glass in the rear. The result is the finest apochromat on the market today.

FS series manual, 1994

FS SERIES

1994/4: New product FS-102 tube (102-820). FS series production start.

1994/7: New product FS-78 tube announcement (78-630).

1994/7: New product FS-128N tube announcement (128-1040).

1994/9/17-30: Astronomical guide October edition: FS-102 & EM-200.

1995/7/22-23: JTB Show'95, FS-78, FS-128.

1997/6/28-29: JTB Show'97, ε-350 and FS-152, EM-10, EM-200USD

1997/7: Paint on the FS series of the objective cell support-mechanism becomes blue.

1997/10: New product FS-152 tube announcement (152-1216).

1998/1: Astronomical guide February edition:  FS-152.

1998/2: New product FS-128F tube announcement (128-1040), 4" focuser.

1998/6/27-28: JTB Show'98, BRC-250, FS-128F.

1999/1: New product FS-60C tube announcement (60-355).

1999/6: The new product FSQ-106 tube announcement (106-530). Modified Petzval desing, 4 lenses / 2 fluorite.

1999/6/26-27: JTB Show'99, BRC-250, FSQ-106, Temma2, TG - SP, NJP.

1999/6: Monthly astronomical July edition ' Telescope Review ': FS-60C.

1999/8: Astronomical guide September edition: FSQ-106.

2000/6: New product FSQ-106N (Kai) tube announcement (106-530), lens shade becomes sliding system.

2000/6/24-25:  J.T.B Show '00, BRC-250, FSQ-106Kai, FS-78C, FS-60C and FCL90 (SKY90), EM-10/200 TemmaPC and TG-SP.

2000/7: New product FS-78C tube announcement (78-630), compact lens shade.

2000/11: New product Sky-90 (FCL-90) tube announcement (90-500).

2001/1: Monthly astronomical February edition test: Sky-90.

2001/2: Astronomical guide March edition: Sky90.

2001/6/23-24: J.T.B Show '01, BRC-250, FSQ-106kai, FS-78C and FS-60C.

2002/11: Astronomical guide December edition: FSQ-106N (Kai).

2004/4: Minor changes in FS series, sliding type lens shade addition, new short version (NSV).

2005: FS series production ended (78, 102, 128, 152), available until stock is exhausted.

2008/4/1: FS-60C minor change, FS-60CB with shorter tube (larger than FS-60CSV), new dedicated reducer f4.2 available.

2010/8/6: New product FS-60Q tube announcement (60-600).

2010/8/31:  CQ-1.7X extender available for FS-60CB.

2012/2/27: Cosmetic minor changes for FS-60CB.

2012/3/1:  FS-60CB & FS-60Q 80th anniversary models announced.

Aperture

(mm)

Focal Length

Limit

Mag

Tube OD

(mm)

Tube Length

(mm)

Weight

(kg)

Image  Circle

(mm)

Image Field

w/RD

(degrees)

Dew Shield

 OD (mm)