Teleskop Service 2.5" Flattener for Refractors

No Reviews yet.
  • Price:
  • Sale
  • Regular price $369.95

Already have gear? Trade it in for cash or new equipment.

Accessories Added


Teleskop Service 2.5" Flattener for Refractors

Teleskop Service 2.5" Flattener for Refractors

TS Optics Field flattener and -corrector for f/9 - f/9 refractors - 61.5mm free aperture. Delivers exceptional field correction for all refractors combined with large camera sensors.

The TS 2.5" flattener's advantages:

Many refractor correction lenses are not able to illuminate even medium-sized sensors without vignetting or other abberations. For this reason, Teleskop-Service has designed a 2" corrector with very good characteristics and which has proven high-level results with many systems: Link to the 2" Flattener by TS

The bigger 2.5" flattener by TS offers the same characteristics but is able to deal with even bigger sensors. Compared with 2" (or smaller T2 systems), this flattener can illuminate full-format (24x36mm) sensors even with fast refractors without vignetting.

The corrector is suitable e.g. for the following refractors:

All systems with a focuser bigger than 2". For all relevant makes, we offer adaptions: Starlight Instruments Feather Touch, Astro Physics, William Optics, Astro Professional and TS Apos. The photographic speed may be between f/5 and f/9.

The 2.5" flattener offers generous back focus:

Like the smaller 2" version, we have designed this flattener with a wide back focus distance. So it is no problem to add Off-Axis-Guiders, filter wheels etc. The recommended distance between the flattener's M69 thread and the focal plane is 91.5 mm for lenses with f/7 and slower.

  • For f/6, we recommend a distance of 106 mm.
  • For f/5.5, we recommend a distance of 111 mm.

The TS field flattener has deliberately been designed without focal reduction:

By concentrating of pure removal of field curvature, an exceptional result has been achieved without secondary abberations like coma or astigmatism. Additionally, the flattener is not limited to certain telescopes or focal lengths. It is universally usable for nearly any refractor from f/5 through f/9.

Technical details:
  • Field flattener for f/5 - f/9 refractors without influencing the focal length
  • Free aperture: 61.5mm
  • Threads on telescope side: M68 male and M63 female
  • Thread on camera side: M69 female
  • Recommended distance between camera side thread and focal plane: 91.5mm

Teleskop Service Product Number: TSFLAT2.5


ManufacturerTeleskop Service


Ask a Question
  • hi I was wondering will this work with gso rc10 truss I have read some wear that does work with rc10 ota but not sure. I'm looking for a flattener to go with my gso rc and qhy9 ccd I have ccdt67 that does work ok. cheers

    Yes, the 2.5" flattener will work, but it takes up a lot of back focus (housing length + 87mm back focus to the CCD on the camera side). A better option for your camera would be to use the TS-RCKORRECTOR, which is 2" but flattens over a 45mm image circle

  • Is the William Optics 90-degree diagonal (Item # WO-M-P90) compatible with this scope? Or is there a new diagonal for visual viewing in development?         

    The WO Star71 is a pure Astrograph and is not designed at all for visual use. It is possible to reach focus with a special short-focus 1.25" diagonal, but WO notes these limitations: This is not a conventional 2" focuser tube with locking thumbscrews. Fo

  • What is the optical length of this flattener?

    The manufacturer does not provide the optical path length of this flattener, but the physical length is 53mm, so the optical path length will be a few mm shorter due to refraction. The recommended distance between the flattener's M69 thread and the