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the world-renowned standard of excellence against which all others six inch Apos are measured

Originally introduced with the avid astrophotographer in mind, the 155mm f7 StarFire EDF (6.1 inch aperture) astrograph features the gigantic focuser and included the Field Flattener lens option accommodating up to Pentax 6x7cm camera format with full field illumination. It made an astounding versatile visual telescope too; capable of extraordinarily wide fields of view at lower magnifications, with the capacity to reveal subtle features on the planets at high magnifications that few other 25 lb. telescopes can show. The astronomy community came to appreciate the versatility of this instrument and at the urging of our customers, we now offer the same excellent 155mm f7 lens in a lighter weight tube assembly incorporating the highly regarded Astro-Physics 2.7 inch focuser.

We continue to be amazed at the compact size of this instrument. At last, a 6.1 inch Apo refractor with an overall length of 40 inches (with dewcap retracted). This is less than half the length of an fl5 and approximately a foot shorter than an f9! In fact, it is about the same length as our 130mm f8, but with an inch more of aperture! You can transport it in a smaller car, store it in less space, invest in a smaller mount and shorter pier/tripod. This instrument is the fulfillment of the astronomer's dream for a truly portable 6.1 inch refractor.


The EDF is superb as a visual instrument. It is easily capable of high-power observations of the moon and planets. Secondary spectrum is totally absent at any power which allows you to discriminate the subtle color variations on the surface of the planets. Deep-sky views are equally impressive due to the very high transmission of the three glass types. Performance will rival larger obstructed systems because the contrast is excellent. Stars snap to focus. Individual stars of globular clusters are sharply etched as intense diamonds against black velvet background. A beautiful sight!

This refractor can, of course, be used photographically with a 35mm camera at prime focus with only a simple camera adapter or at a fast f5.2 with the optional flat- field telecompressor. A single element field flattener is available for the Pentax 6 x 7 medium format camera, however the field is vignetted in the corners due to the restrictions of the 2.7" focuser (full coverage requires the 4" focuser/4" field flattener combination). The 2.7" focuser is interchangeable with the 4" model should you choose at some time in the future to upgrade to the full EDF 4" package.


In the test report entitled "Astro-Physics Refractors Big & Small", in the September 1993 issue of Astronomy, Alan Dyer described the performance of the 155mm f7 EDF during his winter observing sessions. Please note that the article in error referred to this instrument as our EDT.

"Optical performance of the 155EDT was impressive. It produced nary a trace of false color even on Venus. Equally impressive, this scope provided superb images as soon as it was set outside. Even in sub-freezing temperatures, image quality, though not perfect at first, was surprisingly sharp from the start. In cold weather, after a modest settle-down time of 30 minutes, in-focus star images were textbook Airy disks with a well-defined first diffraction ring and a trace of a second outer ring. There was no sign of spherical aberration, lens figure changes, heat plumes, or distorted Airy disks due to tube turbulence."

We could not have said it better ourselves.

Feather Touch<font size=-1><sup>®</sup></font> focuser knobs (24,150 bytes). For 2004 Astro-Physics has developed a new specially designed dual-speed pinion fine dual speed geared focuser assembly. Incorporating a 9 to 1 geared reduction knob, this is the Feather Touch® Micro Focuser option. It is available as an retrofit kit for existing compatible Astro-Physics focusers. Or you can order it factory installed in your new Traveler telescope.

Right: Feather Touch® Focuser option on Astro-Physics 155 mm EDF Apo telescope, optional Astro-Physics 8x 50mm Finder also shown (54,384 bytes).
Click on image for higher quality, enlarged view (125,877 bytes).

Color correction: Less than 0.01 %focus variation from 405nm to 706nm (r to h wavelengths) see table at right
Clear aperture: 155mm (6.1")
Focal length: 1085mm (43") efl
Resolution: 0.74 arc second
Coatings: Multi-layer, overall transmission greater than 97% in peak visual wavelengths
Magnification range: 20x to 600x
Tube assembly: White, 6.5" aluminum tube, baffled, flat black interior, engraved push-pull lens cell
Focuser type: 2.7" I.D. Astro-Physics rack & pinion focuser, 4.5" travel, 2.7", 2" and 1.25" adapters, 2.5" extension
Telescope length: 1041mm (41") with dewcap fully retracted
Tube weight: 23 lb
Carrying Case: Foam-fitted, vinyl-covered plywood case
Carrying Case dimensions: 44-1/2 x 10.5 x 10.5 inches
Carrying Case weight: 15.5 lbs (7 kg)
35mm Photographic field at prime focus: 1.3 x 1.8 degrees @ f7
35mm Photographic field with Telecompressor: 1.7 x 2.4 degrees @ f5.2
35mm Photographic field with 2x Barlow: 0.6 x .9 degrees @ fl4
6 x 7 cm Photographic field at prime focus: 3.2 x 3.7 degrees @ f7 (vignetted)

Astro-Physics 155 EDF Telescope lens transmission (69,285 bytes)

Left: Color correction of the Astro-Physics 155 mm EDF Apo telescope (69,285 bytes).
Click on image for higher quality, enlarged view (178,123 bytes).

  Astro-Physics 13cm f8 EDT in case (47,524 bytes)
  • Company Seven's ATA Transport/Shipping Case: the case provided by Astro-Physics with each optical tube assembly is a reasonable balance of economy and performance for routine storage of a telescope in a temperature and humidity controlled environment. However, if you plan for long term storage, or if you intend to ship the telescope by commercial carrier or transport it as check in baggage on an airliner (observing oversize and overweight restrictions) then your peace of mind and telescope will both be better served with a custom engineered solution - an ATA case by Company Seven.

    Right: Company Seven ATA Case custom fitted for a Astro-Physics 13cm EDT Apochromat Telescope with 2.7 inch Focuser (65,974 bytes).
    Click on image to see enlarged view (215,942 bytes).

    Features include:

      1. custom fit to accommodate the telescope optical tube with or without accessories (Rings, Focuser, etc.)
      2. hand fitted velour lining over foams of varying densities to deal with anticipated loads
      3. weather resistant construction
      4. combination lock and hasp
      5. Fedex/UPS label plate
      6. choice of interior and exterior hard shell material and colors

    Astro-Physics 900 Mount Declination Housing (left side shown), with GTO Keypad Controller, and Counterweight Shaft in optional Company Seven ATA case (94,326 bytes)

    Left: Astro-Physics Model 900 Mount in optional Company Seven ATA case.
    Case 1 of 2 shown here, with Declination housing (left side shown) with GTO Keypad Controller
    and Counterweight Shaft (94,326 bytes).

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