Opticstar/Ascension 102ED Triplet APO Premium & Field Flattener

Premium triplet APO offers fully multi-coated optics and sharp images.

  • Field Flattener included
  • Optical Design: 3-element
  • Optical Glass: premium Japanese FCD1 ED
  • Optical Coatings: Fully Multi Coated
  • Strehl Ratio 0.90 or better
  • Interferometer report included
  • Diffraction limited optics
  • Aperture: 102mm
  • Focal Length: 714mm (f/7)
  • 2" Dual-Speed Rack & Pinion Focuser
  • Retractable Dewshield
  • Vixen-style dovetail
  • Mounting rings with carry handle
  • FREE: accessories (see below)
  • UK warranty
Opticstar/Ascension 102ED Triplet APO Premium & Field Flattener
  • Product code: 102ED3F
  • Availability: In stock
  • Despatch: 2 business days
  • Retail Price: £ 1094.00
Shipping rates
England & Wales
£ 20.00
Scotland Central & South
£ 20.00
Scotland North
£ 40.00
Northern Ireland
£ 40.00
UK islands (from)
£ 40.00
European Union (from)
£ 30.00
Worldwide (from)
£ 80.00

Free accessories included (limited offer)


High contrast and minimal colour aberrations are both highly desirable features in a modern telescope. Triplet lens designs incorporating exotic glasses present optical systems practically free of chromatic aberration (colour fringing) and capable of pin-point star images. An interferometer report with each individual telescope is provided. The included Field Flattener offers field correction to the edge of field, making it a desirable accessory for imaging.

The Opticstar/Ascension APO (apochromatic) refractors use a high quality made triplet lens objective made of premium Japanese ED (Extremely Low Dispersion) glass to achieve images of high contrast and virtually free of secondary colour. Fully (broadband) multicoated lenses ensure maximum light transmission.

Designed with wide field observing and imaging in mind these triplet apochromatic telescopes offer an array of features including a versatile mounting system, precision 2-speed (11:1) Rack & Pinion focuser and removable dew shield. A bracket is included for 50mm aperture finderscopes.





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Optical performance

The Opticstar/Ascension ED Triplet Premium refractors guarantee an RMS of 0.052 (0.90 Strehl) or better clearly outperforming diffraction-limited (RMS 0.071, Strehl 0.82) apochromatic ED refractors.

Also available are the Opticstar/Ascension ED Triplet Premium Plus models that guarantee an RMS of 0.047 (0.92 Strehl) or better.

In imaging terms the high quality FCD-1 objective ED triplet will bring the image in sharp focus when imaging unlike apochromatic ED refractors that rely on a doublet ED objective for imaging.

RMS Rating Strehl Ratio Comments Note
0.094 0.710 --- not diffraction limited
0.071 0.820 Rayleigh Limit (diffraction limited) good
0.057 0.880 --- ---
0.052 0.900 Ascension ED Triplet Premium very good
0.047 0.920 Ascension ED Triplet Premium Plus very good
The Strehl Ratio is calculated from the RMS rating value: Strehl ratio = 1 - (2π x RMS Rating)2


The optical tube greatly benefits from metal knife-edge baffles that prevent light which has bypassed the optical system or which is outside the field of view from reaching the focal plane thus increasing image contrast. At f/7 (102mm) the focal ratio of the Opticstar/Ascension 102ED Triplet is well suited for wide field astrophotography.

Carries full one year UK warranty.

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Opticstar/Ascension 102ED Triplet APO Premium & Field Flattener
Attribute Specification
Opticstar Product Code / sku 102ED3F
Universal Product Code (UPC) n/a
Warranty 1 year UK warranty
Series Ascension APO
Experience Level Advanced
Clear Aperture 102mm
Focal Length 714mm
Focal Ratio f/7
Optical Design Apochromatic Refractor
Optical Elements 3-elements
Optical Glass Japanese FCD-1 Premium ED (extremely low dispersion)
Strehl Ratio 0.90 or better
Optical Coatings Fully (Broadband) Multi-Coated
Focuser 2-speed Rack & Pinion (11:1)
Focuser Drawtube 2-inch with 1.25-inch adapter
Focuser Design Rotatable
Focus Travel 12cm
Baffles Knife-edge
Dew Shield Fully extendable dew shield with aluminium cap
Dovetail Vixen-style
Interferometer Report Included with each invidvidual telescope
Finderscope Bracket Included (bracket for 50mm aperture finderscopes)
Hard Case Not included
Eyepieces Not included
Diagonal Not included
Viewfinder Not included
Field Flattener Included (2-inch) with camera adapters:
• Canon EOS DSLR T-thread Ring adapter (M42 x 0.75).
• Nikon DSLR T-thread Ring adapter (M42 x 0.75).
Assembled Product Weight 5 kg (w/supplied rings & dovetail)
Assembled Product Dimensions 59cm x 13cm x 13cm
Length with Extended Dew-shield 74cm
Transit Weight 6 kg
Transit Dimensions 73cm x 22cm x 27cm
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