Used Takahashi FS102 Doublet-Fluorite Apochromatic Refractor w/Case-UT-12040-SOLD

ITEM #
UT-12040
  • Sale
  • $1,799.00
  • Regular price $2,299.00
  • Used Takahashi FS102 Doublet-Fluorite Apochromatic Refractor w/Case-UT-12040-SOLD

    • Sale
    • $1,799.00
    • Regular price $2,299.00
    • ITEM #
      UT-12040

    0
    Already have gear? Trade it in for cash or new equipment.
    • This is a used telescope in excellent condition

    Used Takahashi FS102 Doublet-Fluorite Apochromatic Refractor w/Case-UT-12040-SOLD

    The FS-102 objective is 102mm aperture, 820mm FL (F8.1 to be exact). It has superb coatings and a high quality, collimatable, temperature compensating cell. The lenses for the FS series were made by Canon-Optron to Takahashi spec’s, like other Takahashi objectives.

    The FS-102 shares the same lens design and cell with its larger and smaller siblings, all of which are ~F8 fluorite doublets with the positive fluorite element on the front (hence the ‘FS’ – Front Surface – moniker). This means the lens is a conventional ‘Fraunhofer’ doublet, like a basic achromat, but with fluorite as the crown.

    In recent years, Takahashi have brought back a fluorite doublet at this size, but it’s rather different with a fluorite-at-the-back Steinheil design, faster f-ratio (F7.4) and optimised for imaging (hence the ‘D’ for digital tag).

    Does fluorite offer a genuine advantage over high-fluoride glass like Ohara’s FPL53 or OK4 (the stuff LZOS make and use)? Possibly. Fluorite is not a glass, it’s a crystalline mineral and it has optical properties that no glass can quite match, including very high transmissivity and low scatter. The FS manual has this to say:

    “… the use of multi-coatings further increases light transmission over any ED glass. This makes any fluorite objective brighter than any comparable glass objective …”

    Does putting the fluorite at the front make for a worse optic, as some have claimed? I believe not. Check-out the excerpt from the FS manual below.

    Independent tests have found the FS-102 to be a true apochromat, whereas ED doublets (think TV-102) often aren’t. Takahashi’s own spot diagrams suggest that the FS-102 is less well corrected at the violet end than the TSA-102 triplet (so less good for imagers), but better in the yellow, orange and red (great for Mars).

      Additional Information

      ConditionExcellent
      ManufacturerTakahashi
      Warranty90 Day
    • Takahashi FS102 fluorite optical tube
    • 1.25" diagonal
    • 18mm LE eyepiece
    • Custom foam lined hardwood case

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