Company Seven | Astro-Physics 305mm f3.5 / 12 Inch f3.8 …

Astro-Physics 305mm f3.5 / 12 Inch f3.8 Riccardi-Honders Astrographic Telescope (P/N 305RHA)An amazing 1,160mm f3.8 Apo Lens!

Development of the Riccardi-Honders Design

Astro-Physics Company are known for making the world’s most advanced, versatile, and desired lines of apochromatic refractor telescopes. In 2000 after more than a decade of research and development to “get it right” they surprised the astronomy community with the announcement of their first production Catadioptric telescope. This is designated the Astro-Physics Astro Physics 10″ f14.6 Maksutov-Cassegrain telescope, a compact 33 lb. (15 kg) high resolution instrument designed to provide refractor like views (and images) of the brighter, small objects including the planets, moon, double stars, and the like.

Right: Astro-Physics 305mm Honders telescope (OTA to the left) as introduced in 2009 atop the Astro-Physics 3600GTO ‘El Capitan’ German Equatorial Mount (79,387 bytes). Image courtesy of David Illig.Click on image to see enlarged view (253,556 bytes).

Since then Astro-Physics has been working to perfect a new catadioptric telescope, one ideally suited for imaging wide areas of sky and not compromised by considering visual applications. This new telescope would be compact, perform well in temperature extremes around the world, and meet their traditional exacting requirements for optical and mechanical excellence. The result is a telescope that is the first of its kind: the Astro-Physics 305mm f3.8 Astrograph. The ‘Honders” as it is known here at Company Seven and in most of the community is based on Klaas Honder’s original idea of a fast optical system using a crown glass objective and meniscus correcting mirror in a Newtonian configuration. By adding a secondary mirror and field lens, Italian designer Massimo Riccardi was able to design an ultra-fast (short focal ratio) astrograph using only comparatively affordable crown glass elements. Astro-Physics has added their more than years of telescope design experience to create a truly unique and fast astrograph to take full advantage of today’s CCD imaging cameras. With this telescope you will collect photons most efficiently producing wide-field of view images that you could previously only have imagined.

A further goal in this development effort was to equal or to approach the performance of their highly prized triplet apochromatic refractors in at least certain applications. One thought in producing these Catadioptric telescopes is that if a number of customers who do not require the versatility of the Apo refractors (which perform superbly well at extremely high magnifications, and down to very low magnifications) will order the Mak telescopes instead of the triplet Apos then this may take some of the burden from the Triplet production line, and thereby help Astro-Physics to satisfy a far greater number of the more demanding amateur and professional clientele.

In April 2008 Roland Christen had presented a paper entitled “Optical Design for High Resolution Imaging” discussing the advantages of the Riccardi-Honders optical design. The prototype 305mm f3.8 Riccardi-Honders Astrograph prototype was introduced to the public on 18 April 2009 (image at right) although by then it had already proved itself with numerous amazing images taken while at the Astro-Physics observatory. It was shown mounted in parallel with the prototype 305mm f12.5 Maksutov-Cassegrain telescope atop the Astro-Physics 3600GTO ‘El Capitan’ German Equatorial Mount. Pricing was announced in August 2010 as the first invitations to order were sent out. Deliveries from the first production run will commence in limited numbers in the Fall of the year 2010.OPTICAL CHARACTERISTICS

The system includes the optical tube assembly, a 3.5 inch diameter focuser, Dewcap (Lens Shade), Dust Cover, pair of Mounting Rings, and Carrying Case. Company Seven will offer an optional Airline Transport Association Approved (ATA) shipping case for this instrument.

Any optical imperfections such as a degree of surface roughness and zonal errors on the optical surface will compound the problem.Astro-Physics tested a commercial telescope where the central obstruction, optical errors and surface roughness were large enough to cause the first diffraction ring and central Airy disc to have almost equal brightness (with a 35% obstruction, theoretically there should be at least a4 to 1 difference). Even so, this sample telescope “tested” very well on the star test – it had quite similar inside and outside Fresnel patterns and might be judged to be textbook perfect by the star test. Yet it was a very poor performer on all but the most steady of nights, when the seeing was essentially perfect. The slightest motion in the atmosphere would result in a display of “cotton ball” stars. This is one reason whyAstro-Physics and Company Seven have not been a major fans of the “star test” to evaluate the actual performance of a telescope. The only unbiased way to measure an optic is with interferometry, or by an MTF (modulation transfer function) test, or with a PSF (point spread function) test, which measures the relative strength of the Airy disc versus the diffraction rings with the image in focus.

Astro-Physics has endeavored to achieve the highest absorption of stray light possible by employing state of the art baffling and anti-reflection techniques; this will help to provide the user with maximum contrast. The exterior of the telescope is finished in a durable textured off white finish, with black anodized focuser and cells; these will retain their beauty for many years. You will appreciate the unique design and fine craftsmanship of this telescope.

Knife edge baffles are machined into the walls of the telescope optical tube and of the focuser draw tube, these and painted flat black in order to maximize contrast by essentially eliminating any internal reflections. The inside diameter (I.D.) of the draw tube permits the avid astrophotographer to employ up to a 35mm format film or CCD camera to capture images. While this is designed as an astrographic instrument, you can attach a Barlow lens then attach standard 2 inch diameter accessories, and with the furnished 1.25 inch adapter (threaded for 48mm filters) to use common oculars and accessories too. Recessed brass locking rings are installed at each thumbscrew location; as you tighten a thumbscrew a brass locking ring clamps onto the part that has been inserted; consequently the focuser draw tube and any accessories are held securely in place and will not mar the surface of your accessories. This is particularly important considering the heavy and expensive accessories that you may use.

* Specifications are subject to change without notice.

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:

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 Controllerand Counterweight Shaft (94,326 bytes).

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Company Seven | Astro-Physics 305mm f3.5 / 12 Inch f3.8 …

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