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140mm f7.5 EDF AIR-SPACED APO REFRACTOR (5.5" aperture)
"the latest high tech Apo design series"
Still proving "Made in The USA" can mean something great! This 140mm Starfire EDF is the sequel to and smaller cousin of the proven 160mm Starfire EDF. This series introduces the most recent high tech Apo designs incorporating triplet apochromat lens arrangement. This is the culmination of years of optical research by Roland Christen, President and optics designer of the Astro-Physics Co. It is made with the best available grades of optical glass to achieve exceptional image brightness and excellent color correction. And it incorporates the latest in high efficiency multi-coating technology to improve light throughput through the six air spaced surfaces.
Right: Roland Christen with his new Astro-Physics 140 EDF telescope OTA. This prototype telescope is shown with 2.7 inch focuser, and with lens shade (absent the AP model decal) extended. The telescope is installed onto the optional 900 GTO German Equatorial Mount (91,659 bytes).
Click on image to see enlarged view (98,922 bytes)
The 140mm EDF was announced on 28 April and we began to accept orders for these telescopes in September 2007. Roland designed this telescope with approximately the same focal length as the original and highly successful 155mm f7 EDF Starfire (as well as the 130 f8 EDT and the original 5 inch f8.3 Starfires), so that the 140mm can be used with all of the same specialized film astrophotography and CCD imaging accessories that were originally designed for these earlier telescopes. Visual astronomers will enjoy the 1,050mm focal length and versatile focal ratio which permit the use of a full range of eyepiece designs from simple to complex to produce extremely sharp planetary images. This design effort also produced mechanical refinements of the Optical Tube Assembly and Focuser. The 140mm EDF is offered for sale with the customers choice of either the Astro-Physics 2.7 inch (P/N 140EDF27) or with the 4 inch (P/N 140EDF4) diameter focuser. We are certain that astro-imagers as well as visual observers will find this scope a real joy to use.
Deliveries of the first version of this design 160mm Starfire EDF, began in December 2004. The first of our 160mm EDF instruments (with the Feather Touch® Micro Focuser option ) arrived in August 2005 and was placed on display in Company Seven's showroom collection for those who wish to see it alongside many of the other popular Astro-Physics telescopes.
PERFORMANCE
The EDF series telescopes are each superb as a visual or imaging instrument. These employ Super ED glass (ED stands for extra low dispersion, Vd> 90) that provides color free performance at this focal ratio. Images of stars and planets are presented in their natural colors, and daytime objects appear sharp and contrasting without annoying purple fringes. The 140mm EDF is easily capable of high-power observations of the moon and planets. The color correction is ideal for visual uses being completely free of false color; secondary spectrum is totally absent at any power and this allows the observer to discriminate the subtle color variations on the surface of the planets. Deep-sky views are equally impressive due to the broad range of possible fields of view (from low magnification to high), and very high transmission of the three glass types and advanced multi-coatings. With the optional Visual Telecompressor at f/5.6 one can enjoy fields of view of up to 3.3 degrees at 19X with a suitable eyepiece! Performance will rival much larger obstructed systems because the contrast is excellent; stars snap to focus, individual stars are sharply etched as intense diamonds against black velvet background - a beautiful sight!
The objective lens consists of a positive element of Super ED glass surrounded by two matching hard crown meniscus lenses. The two outer elements are chosen so that the combination is free of coma, spherical aberration and other higher-order aberrations. Under steady viewing conditions, you will see a hard white Airy disc at focus surrounded by the first diffraction ring. Inside and outside of focus, you will see an evenly illuminated, expanded disc with concentric Fresnel rings, the outermost ring brighter and wider than the rest.
Right: Astro-Physics 140 EDF lens design "Chromatic Focal Shift" data between .460 to .656 microns. Note the focus shift position for each wavelength (color of the spectrum) relative to the zero point, as well as the the Diffraction Limit Range. The total false color does not exceed plus or minus 0.053mm or 0.0045 percent of the focal length - quite extraordinary! (91,981 bytes)
Click on image to see enlarged view (131,980 bytes)
The 140mm EDF is an air-spaced lens arrangement engineered for rapid cool down during night time temperature swings, so this telescope is practical for use in temperate as well as very cold climates. On most nights, the settling down time for the lens is between ten to fifteen minutes, and even in subfreezing conditions it rarely takes more than forty five minutes to stabilize.
MULTI-COATINGS
A multilayer coating is applied to the six air spaced lenses of this telescope to prevent light reflection off the surface of, or between the lenses. This helps to eliminate ghost images and flare and can improves color rendition, achieving a dramatic increase in image contrast. The coatings provided are a recently developed multilayer antireflection coating; this provides a cumulative light transmission greater than 97% across the peak visual wavelengths and improved durability over prior choices. While Astro-Physics has previously produced some air spaced lenses, these air spaced lenses tended to incorporate less efficient Magnesium Fluoride antireflection coatings or at times some then risky multi-coating technologies were tried. The very costly, precisely polished and figured ED glass lens elements undergoing these older processes were at risk by exposure to very high temperatures in the chamber as the coatings were flashed onto the lens. Heating or cooling a large piece of glass could produce immediate breakage or in some elements start in motion a problem that might become apparent years later. And after the process, these coatings could be damaged by something as simple as a grain of sand accidentally wiped across the lens surface. So among the reasons why Roland decided to move to oil spaced designs in the 1980's was to avoid the risks imposed by these older coating techniques.
Since the prior EDF design was introduced in 1989 a number of new low temperature coating technologies have been developed which produce a very hard and durable coating. These also can provide superior light throughput compared to what was previously available. So now the average loss due to reflections from a surface across the photo-visual spectrum can be less than 0.5%. Since these technologies have come about, it is now possible for Astro-Physics to produce air spaced lenses with acceptable throughput. And the durability is increased since the new coatings are actually fused into the glass surface.
The improvement of the new coatings over those provided with previous EDf models is apparent even to the naked eye. With the increase in light throughput and reduction of possible ghosting due to the new multi-coatings, the new 160 EDF spherical design becomes practical. Astro-Physics can eliminate the time consuming aspherizations process employed to make the previously EDF series, while continuing to produce a highly corrected lens.
IMAGING APPLICATIONS
The choice of focuser means those who seek the most manageable version of a high performance Apo can save money and weight. Company Seven recommends those who will use the telescope primarily for visual applications should choose the 2.7 inch focuser. The 2.7 inch focuser can accommodate CCD or film cameras with up to 35mm formats. However, the 4 inch focuser is preferred for those who will use medium format film or CCD cameras, for those for whom weight or cost is not a concern, and for anyone who anticipates becoming deeply involved in imaging sooner or later since this will make it more likely that you will have more flexibility in the selection of CCD cameras and accessories. But keep in mind that these focusers can be readily interchanged and so if you start off with the 2.7 inch focuser then you could buy and install a four inch focuser later.
This high degree of correction serves as well as for film or CCD imaging needs. This refractor can be used photographically with a 35mm Single Lens Reflex (SLR) digital or film camera at prime focus with only a simple camera adapter or even faster at f/5.75 with the new optional matched flat-field telecompressor. An optional matched field flattener is available for use with the Pentax 6 x 7 medium format camera with full coverage provided by the provided four inch focuser and optional field flattener.
As CCD camera technology has advanced the quantum efficiency has improved. These devices are now can have good sensitivity beyond the visual into the UV (< 400 nm) and the IR (> 700 nm) portions of the spectrum.
YOU WANT PROOF?
COMPARISON WITH PRIOR EDF
Many will wonder how this telescope compares to the prior generation of the AP Apos which were announced at Company Seven on 1 December 1989 and then came to dominate the market from then until now. Astro-Physics chose to make the new Apo with a 140mm clear aperture instead of what was typical of the prior 130mm f8 Starfire EDT. The 140mm EDF has a theoretical light gathering power of about 400X that of the unaided human eye (based on a 7mm exit pupil), while the 130mm EDT provides about 345X. So the 140mm will produce an image that will appear perceptibly brighter to the eye than its predecessor, somewhat "faster" for film imaging, and this while maintaining about the same focal length.
Right: Astro-Physics 140mm EDF's larger cousin, the 160 EDF Telescope objective lens and cell with lens shade extended (40,735 bytes)
Click on image to see enlarged view (178,424 bytes)
The new 160mm and 140mm EDF lenses have slightly better visual color correction over the spectral range from 400 to 700 nm than the predecessor. The previous EDF/EDT lens design had slightly worse visual correction over this range, but somewhat better color correction to 1000nm in the IR; this factor is not very relevant to most who are involved with CCD imaging since IR blocking elements or coatings are frequently employed in their imaging systems.
With a 1,050mm (41.3 inch) focal length the 140mm remains quite versatile, the differences in physical overall length between the stored 130mm EDT or the 155mm EDF and the 140mm EDF OTA's are moderate. The f/7.5 ratios permit the use of a full range of eyepiece designs - from relatively simple to complex (as long as they are well made) to produce extremely sharp planetary images. This f/7.5 is a bit longer ratio than that provided with the prior 155mm EDF's 1,100mm (43.3 inch) f/7.1.
In production the EDF oiled design objective requires all the external and internal surfaces must be polished fully, and then the lenses are carefully matched and corrected to one other which includes a time consuming apsherization process. The current EDF design still requires a highly perfected polish as with the prior design however, this EDF is more spherical and this makes it somewhat easier to finish than the prior generation of EDF. And in these EDF's the curves of the opposing elements differ.
The Astro-Physics company has evolved over the years to include several of the best experts in lens design and figuring. Their reputation for consistent perfection is unrivaled. And incidentally, as before Astro-Physics will continue figure the lens sets of the EDF to 1/50 RMS - these are nulled in the yellow-green portion of the spectrum where the human eye is most sensitive and the wavelength more revealing of any anomalies than testing in Helium Neon red light as is typical in many other factories. As related by Roland Christen when discussing the 160mm EDF:
"All polishing including hand correction is always done on a machine. Steep
curves are no worse to polish to high accuracy than shallow ones. In fact, very
shallow curves are the most difficult to get right. For an apo triplet, every
surface must be matched to a very high tolerance level to an interferometric
test plate. Only if this is done will the spherical and color correction come
out right. Apo doublets have slightly lower requirements, and achromats have
much looser tolerance for color correction than a triplet lens."
There are many ways to polish a glass surface, and the oft used words
"machine polished" really means very little. There is no-one in this business
that pushes glass around by hand. There is a vast difference between precision
polishing and rapid polishing of a surface. Rapid polishing can clear a ground
surface is 10 minutes or less. Some new processes can do it even faster - a few
seconds for a 6" part. The surface will not be very good in either case, and
will have machining marks and zones on a microscopic level. Precision polishing
takes many hours with specially made pitch laps. That's the only way to get
consistent high surface finish."
MECHANICAL CONSTRUCTION
As has been the case for more than a decade, these optical tubes remain the standard of excellence in mechanical design as well as in optics. The mechanical construction provides this telescope will be completely trouble-free, and the optics will remain permanently aligned unless it suffers some catastrophic injury. The gorgeous tube assembly is precision machined in the Astro-Physics shop with the most modem CNC equipment available; there are no fragile die castings in this telescope. Expert machinist transforms solid, aircraft-quality aluminum stock into a fully baffled tube assembly with no less than twelve knife-edge baffles in the focuser draw tube alone. Astro-Physics has has endeavored to achieve the highest absorption of stray light possible to give you the maximum contrast.
The exterior textured finish of the optical tube and dew cap will retain its deep, lustrous beauty for many years. The texturing also reduces the chances of the optical tube sliding in the rings or in your hands (particularly when wet with dew for example) than the original gloss white finish provided with the early 1990's EDF models. You will appreciate the unique design and fine craftsmanship of this telescope - even on cloudy nights you might be content to stay home and just look it over.
The objective lens resides in a push-pull cell that maintains its collimation even under conditions of vibration during shipping. The newly designed captive sliding felt lined dew cap (lens shade) features an integral baffle placed at the leading edge to help prevent dew accumulation as well as to block stray light.
The 140 EDF optical tube assembly incorporates either the Astro-Physics 2.7 or 4 inch focusers developed by Astro-Physics. These were developed by Astro-Physics, and have been refined over the years to accept a broad range of heavy equipment while still moving smoothly throughout the full range of focus travel without image shift. The larger 4 inch focuser was developed to to permit wide field astrophotography with their larger EDF telescopes.
Above Left: Astro-Physics 160mm Starfire EDF telescope with four inch focuser shown with optional Astro-Physics "Maxbright" Mirror 2 Inch Diameter Diagonal
and Astro-Physics 8mm Super Planetary Series Eyepiece (88,614 bytes).
Click on image to see enlarged view (237,080 bytes).
Above Right: Astro-Physics 2.7 inch Focuser with Feather Touch® Micro Focuser on an AP telescope. (53,738 bytes)
Click on image for higher quality, enlarged view (151,858 bytes).
The superb Astro-Physics focusers are a finely crafted units with several unique features:
- Helical rack and pinion arrangement provides smooth motion, free of backlash or wobble, for precision focusing.
- The 2.7 inch model provides an inside diameter (I.D.) of the focuser draw tube of 68mm (2.7 inches). This allows the visual astronomer to employ any eyepiece made, even our largest TeleVue "Über Eyepieces" such as the 41mm Panoptic or the 31mm Nagler. While one can also attach optional Astro-Physics field flattening or telecompressor lenses and hardware to accept a 35mm format film or CCD camera to pursue astrophotography images.
- The 4 inch model provides an inside diameter (I.D.) of the focuser draw tube of 109mm (4.3 inches). This allows the avid astrophotographer to employ optional Astro-Physics lenses and hardware to attach a medium-format camera to capture images in a 6 x 7 cm format with no vignetting.
- The components are machined to extremely high tolerances, assuring that there is no rotational or lateral wiggle between the draw tube and housing.
- More than a dozen knife-edge baffles are machined into the wall of the draw tube and painted anti-reflection black in order to maximize contrast by essentially eliminating any internal reflections.
- Recessed brass locking rings are installed at each thumbscrew location. As you tighten each thumbscrew, the brass locking ring clamps onto the part that has been inserted. Consequently, your focuser draw tube and accessories are held securely in place. This is particularly important considering the heavy and expensive accessories that you may use. As an added advantage,
the brass will not mar the surface of your accessories.
- The telescope is designed with the astrophotographer in mind and so it incorporates the Feather Touch dual-speed geared manual focus control. While the Focuser can be precisely rotated a full 360 degrees. These features allow more accurate focus, and the optimal composition of the image whether in the eyepiece or camera.
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The built-in collar allows the user to loosen the focuser and rotate it smoothly on the optical tube throughout a full 360 degrees of travel to suit - all without the need of tools or loss of critical alignment.
- Advanced engineering eliminates the need to grease the focuser drawtube thereby eliminating a magnet for contaminants, and reducing "stickiness" when focusing which may have been encountered with other focusers on very cold nights.
- Two pair of tapped and threaded holes are provided located at the 10:30 and 1:30 clock positions on the Focuser Housing. These facilitate the attachment of accessories (finder telescope, etc.).
- Focus travel is a generous as the drawtube extends 105mm (4.1 inch). And the focuser is positioned on the optical tube so that the Baader Planetarium/Carl Zeiss Mark V Großfeld Binocular Viewer will come to focus with or without it's provided 1.25x compensator. This allows the user to see glorious wide field views with both eyes - a real treat.
- In 2004 Astro-Physics developed a new specially designed dual-speed pinion fine dual speed geared focuser assembly for their 2, 2.7 and 4 inch Focusers. Incorporating a 9 to 1 geared reduction knob, this is the Feather Touch® Micro Focuser option. You can order it factory installed in your new 140mm EDF telescope. It is also available as an retrofit kit for existing compatible Astro-Physics focusers.
Right: Feather Touch® Focuser shown option on Astro-Physics 155 mm EDF Apo telescope 2.7" Focuser, becoming available with the 4" model (54,384 bytes).
Click on image for higher quality, enlarged view (125,877 bytes).
You can use the larger or standard slip accessories on this focuser since it is provided with reducers to accept optional 2.7 inch accessories, and another reducer to accept 2 inch accessories, and a reducer of from 2 to 1.25 inch. For those who wish to employ the telescope in a straight through arrangement we also provide a 4 inch wide x 2-1/4 inch long extension tube which attaches onto the focuser drawtube bayonet mount.
There are a number of current and coming photographic accessories for CCD imaging, 35mm and medium format film photography for this telescope. In addition to an optional 2.7 and 4 inch Prime Focus Field Flattener for medium format or 35mm applications, we offer a new dedicated f/5.75 Flat-Field Telecompressor for the 4 inch focuser that is diffraction-limited over the entire 35mm field; this is perfect for use with the latest larger format CCD systems available today including our Santa Barbara Instruments Group new Research Series CCD systems.
140mm f7.5 EDF OVERVIEW:
Measurements based on preliminary data, we will revise this after the first production sample is delivered to Company Seven
| SPECIFICATIONS |
| Color correction: |
Less than 0.005% focus variation from 706nm to
405nm (h to r) see table above right |
| Clear aperture: |
140mm (5.5") |
| Focal length: |
1,050mm (41.3") |
| Resolution: |
0.83 arc seconds |
| Coatings: |
Multilayer broadband, total transmission greater than 97% in peak visual wavelengths |
| Magnification range: |
14x to 500x |
| Tube assembly: |
White finish aluminum tube; fully baffled,
permanently aligned cell construction; engraved focuser |
| Focuser type: |
Rotating 2.7 or 4" Astro-Physics rack & pinion 9:1 gear reduction;
4/2.7, 2 and 1.25" adapters; 2.7/4 x 2.25" extension tube |
| Telescope overall length: |
37 inch (940 mm) w/dew cap retracted |
| Telescope Tube diameter: |
6-1/2 inches |
| Dew Shield diameter: |
6-1/2 inches |
| Weight with dew cap: |
27 lbs. (12.3 kg) |
| Carrying Case: |
Foam-fitted, vinyl-covered plywood case |
| Carrying Case Dimensions: |
42 x 12 x 11 inches |
| Carrying Case Weight: |
19 lbs. (8.7 kg) |
| 35mm prime-focus field: |
1.9 x 1.3 x 2.3 degrees |
| 35mm telecompressed field: |
2.5 X 1.7 degrees at f/5.63 |
| 6 x 7 cm prime-focus field: |
3.8 x 3 x 4.8 degrees |
* Specifications are subject to change without notice.
Right: Astro-Physics 160 EDF Telescope objective lens and cell with Dew Shield/Lens shade extended (15,134 bytes)
Click on image to see enlarged view (173,595 bytes)
ACCESSORY SUGGESTIONS
- A suitable German Equatorial Mount and mount attachment hardware such as those developed by Astro-Physics. These portable mounts are perfect for visual and photographic studies in either the Northern or Southern Hemispheres. Another very capable astrographic German mount that is not costly as the Astro-Physics mounts and more readily available is the Losmandy G-11 German Equatorial Mount.
- Mounting Rings:
For the 140mm EDF these will be the 6.5" Rings, sold by the pair as P/N 65RING.
- Mirror Diagonal:
Prism diagonals may introduce aberrations which degrade perceived image quality. Since this is especially noticeable in telescopes with fast focal ratios, we recommend use of the Astro-Physics "Maxbright" Precision Mirror 2 Inch Diagonal.
- Eyepieces:
Astronomers will wish to own at least a few 1.25" or 2" eyepieces initially to set up this telescope to address:
- Low magnification: for views of the faint deep sky objects a 32mm to 41mm focal length eyepiece.
- Middle Magnification eyepiece - usually between 80 to 120X, for views of the full Moon, Star Clusters, etc.
- High magnification: 200X and more for views of the planets
Astro-Physics and Company Seven recommend the eyepieces of advanced designs such as those pioneered by Al Nagler, founder of the TeleVue company. TeleVue's advanced designs include the "Nagler", "Radian", or "Panoptic" series eyepieces. These oculars will provide the widest angle clear, and flat field images bringing out the most in this (and many other) telescopes.
And for those who seek the most detailed images of the planets or close double stars, you should also consider the new Astro-Physics Super Planetary Eyepieces.
Examples of some popular eyepiece choices:
| Eyepiece |
Magnification |
Actual field of view |
Exit pupil |
| 55mm Plossl |
19x |
2.5 degrees |
7.3mm |
| 41mm Panoptic |
26x |
2.5 degrees |
5.5mm |
| 35mm Panoptic |
30x |
2.1 degrees |
4.7mm |
| 22mm Nagler Type 4 |
48x |
1.7 degrees |
2.9mm |
| 12mm Nagler Type 4 |
88x |
.49 degrees |
2.9mm |
| 10mm Radian |
105x |
0.57 degrees |
1.3mm |
| 9mm Nagler |
171x |
0.57 degrees |
0.9mm |
| 6mm Super Planetary |
175x |
0.24 degrees |
0.8mm |
| 5mm Radian |
210x |
0.38 degrees |
0.7mm |
| 5mm SPL |
210x |
0.19 degrees |
0.7mm |
| 3mm Radiam |
350x |
0.18 degrees |
0.4mm |
You may slso consider using our Astro-Physics 2" (2X) Barlow to double your magnification, and increase overall versatility of your eyepiece selection.
- Field Flattener for medium format photography - matched to the performance characteristics of this instrument.
- Photo-visual flat-field Telecompressor f/5.6 for use with 1.25 or 2 inch eyepieces - enjoy fields of view of up to 3.3 degrees with a suitable eyepiece!
- TeleVue "Starbeam" Sight: Beautifully machined and black anodized aluminum, on a quick release machined hardware. Battery powered illuminator is adjustable in brightness; it projects a 10 arc minute diameter red dot onto a transparent 40mm clear aperture window so that the dot appears to be over wherever the scope is pointed. Six arc minute accuracy make "star hopping" easy.
- Red LED Flashlight such as the Rigel Skylite to help one set up and use a telescope, and to read charts or a planishpere without adversely impacting the observers night vision.
- Telescopes such as this often put the eyepiece at position that is only about 3 or 4 feet (0.9 or 1.2 meters) from the ground. Since most of our customers are taller than that, they will find it uncomfortable to stand bent over to observe for extended periods. For a much more enjoyable and comfortable observing experience, Company Seven recommends the Observing Chair; this is our most comfortable, flat folding, adjustable height seat. It is not inexpensive, but is so practical and can be used for camping or other times when a comfortable portable seat is desired.
- 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:
- custom fit to accommodate the telescope optical tube with or without accessories (Rings, Focuser, etc.)
- hand fitted velour lining over foams of varying densities to deal with anticipated loads
- weather resistant construction
- combination lock and hasp
- Fedex/UPS label plate
- choice of interior and exterior hard shell material and colors
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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Contents Copyright 1994-2007 Company Seven - All Rights Reserved
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