ASTRO-PHYSICS HISTORY
155mm f7 Starfire EDF 6.1" aperture (155EDF)

ASTROGRAPH WITH 4" FOCUSER AND 4" FIELD FLATTENER

The 155mm f7 StarFire EDF is not available to purchase and we do not have any plans to produce additional scopes with these exact specifications. This information is presented for present owners and those who are curious about its history. If you are one of the lucky owners, you may want to consider some of these accessories.

155mm f7 StarFire EDF, 900GTO German Equatorial Mount, 48" Portable Pier, one 10 lb. and one 18 lb. Counterweight and other accessories

This 155mm f7 StarFire EDF (6.1" aperture) was designed to be the ultimate astrograph while providing uncompromising visual performance. Outstanding photographs published in Sky & Telescope, Astronomy and various international astronomy magazines can only hint at the detail of the original prints and negatives. The 30" x 40" prints of the Lagoon/ Trifid and Horsehead Nebulas that are on display in our showroom show incredible pinpoint star images from one side of the print to the other with no sign of image degradation. Truly amazing! Photographic spot diameters measure 15-20 microns over a 5 degree field (4" circle). The fast f7 focal ratio captures elusive and faint deep-sky objects easily with incredible detail. This lens has outperformed mirror type astrographs twice its size, as we had predicted. Be sure to enjoy the images in our gallery taken with this telescope.

The EDF is superb as a visual instrument as well. It is easily capable of high-power observations of the moon and planets. Secondary spectrum is nearly absent at any power. Deep-sky views are equally impressive due to the very high transmission of the three glass types.

In the astrographic configuration, the lens is a 5-element design in 2 groups (3 elements in front, 2 in rear). The heart of the front triplet apochromatic lens is an ED glass and 2 crowns. This combination essentially eliminates all secondary spectrum, coma and spherical aberration. The rear lens is a 2-element field flattener that eliminates astigmatism and field curvature. In the visual configuration, the rear 2-element lens is removed and replaced with a standard visual adapter. This adapter allows all our usual accessories to be attached, as well as all standard 2" and 1.25" oculars.

The tube assembly comes fully baffled for a 5 degree 4" field. The giant 4" focuser is silky smooth and can be locked for long time-exposure astrophotography. Although it is possible to attach your own custom-made film holder, we have determined that the most practical camera back is the Pentax 6 x 7cm medium-format camera. Field coverage is 3 x 3.5 degrees. After many years of field research, we chose this camera because it holds the film critically flat without the use of special vacuum attachments. This is not the case with other, less expensive film backs. The Pentax allows the user to critically focus directly on the ground glass with a high-power magnifier, assuring the highest possible resolution.

Another feature is the extra-large opening and minimum back distance to the film plane which minimizes the inevitable vignetting of the light in the extreme corners of the format. All the important color and black/ white films are available in the 120 format, which is not the case with larger formats. It is for these reasons that we have standardized on the Pentax 6 x 7 and offer all the attachments necessary to use with the 155mm EDF.

The Astro-Physics giant 4" focuser is truly versatile. The 4" ID of the drawtube will allow maximum coverage of the Pentax 6 x 7 cm negative for medium format photography. The inside of the drawtube has a series of knife-edge baffles for maximum contrast. When you wish to use your 35mm camera with the field flattener you can attach the camera adapter (67RT--, specify the t-ring) directly to the bayonet and you are ready to go. You can use our special CCD adapters to couple your favorite CCD camera to this field flattener as well to obtain exquisite images, especially with the large chips available today.

For for even faster exposures (f5.2), use our Telecompressor (27TVPH) and Camera Adapter (PFCT--, specify the t-ring). Note, the Telecompressor cannot be used with the field flattener; they are separate and distinct optical designs. The 2" and 1.25" adapters will allow you to use all of our standard accessories to maximize your visual and photographic applications.

The 900GTO or 1200GTO German Equatorial are recommended for astrophotography, depending on your requirements for portability and the amount of wind you are likely to encounter at your photographic site.

Specifications
Color correction Less than 0.01% focus variation from 405nm to 706nm (r to h wavelengths). Color correction curves.
Clear aperture 155mm (6.1")
Focal length 1085mm (43")
Resolution 0.74 arc seconds
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, push-pull lens cell, engraved retaining ring
Focuser type 4.0" I.D. Astro-Physics rack & pinion focuser, 4.15" travel; 2.7", 2" and 1.25" adapters; 2.5" extension
Telescope length 1041mm (41") w/ dewcap fully retracted
Weight with dewcap 27 lbs. (12.3 kg)
Field flattener 4" diameter, 2-element with multi-coatings
Carrying-case type Wood case with grey vinyl covering and foam-lined interior

Photographic Field
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 0.9 degrees @ f14
6x7cm Photographic field at prime focus 3.2 x 3.7 degrees @ f7

Reviews and Related Articles

Author Unknown. "One Amateur's View of the Heavens", SkyWatch '99, pp. 110-112, featuring Carl Weber.
Dyer, Alan. "Astro-Physics Big & Small", Astronomy, September 1993, pp. 62-67.
Hallas, Tony and Mount, Daphne. "Fuji's Miraculous Super HG 400, Astronomy", September 1990, pp. 62-64.
Gross, Todd. http://www.weatherman.com/scope.htm "Astro-Physics AP130 f/6", 1999.
Ting, Ed. http://www.scopereviews.com/page1d.htm "Astro-Physics 155 EDFS", 09-18-00

Recommended Accessories
0.76x CCD Telecompressor Corrector for 155 f/7 @ f/5.3 and 140 f/7.5 @ f/5.7 (155TCC)
2" Convertible Photo-Visual Barlow (BARCON)
Maxbright 2" Mirror Diagonal (PMDMAX)
Mark V Binocular Viewer (BPMARKVS)
Kendrick Dew Remover Heater (KDR004) and Controller
Kendrick Solar Filter for 155mm StarFire EDF with Baader AstroSolar Density 5 (KDRA155V)
Kendrick Solar Filter for 155mm StarFire EDF with Baader AstroSolar Density 3.8 (KDRA155P)

There are many other accessories to consider. Please refer to these sections for additional recommendations:
Visual Accessories
Photographic and CCD Imaging Accessories
Baader Planetarium Filters
AstroSolar Solar Filter Material

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Copyright 2004 Astro-Physics Inc. All rights reserved.
Last modified: June 13, 2012

Astro-Physics, Inc.
11250 Forest Hills Road, Rockford, IL  61115, U.S.A.
Phone: 815-282-1513   Fax: 815-282-9847