Sky-Watcher Evostar ED72 refractors provide the finest images obtainable in their design class. These doublet refractors deliver dramatic, coal-black skies and faithful, contrast-rich views of planetary and deep-space phenomenon that are second to none. Sky-Watcher Evostar refractors are the logical choice for the discriminating amateur astronomer looking for an investment in advanced instrumentation for exceptional viewing and astrophotography, the focus position is designed for use with a camera.

This telescope is designed to be used as an astrograph, it short focal length make it ideal for imaging large star fields without the need for a large astronomical mount. However, we suggest the Skywatcher 0.85x Reducer / Corrector to flatten the wide field for better imaging results

It is also a perfect scope for Autoguiding with the addition of the ZWO ASI 120Mini Guider camera

FEATURES:

Capturing impressive deep-sky astroimages is easier than ever with Celestron’s Rowe-Ackermann Schmidt Astrograph (RASA 11) V2, the perfect companion to today’s top DSLR or astronomical CCD cameras. This fast, wide-field f/2.2 system allows for shorter exposure times compared to traditional f/10 astroimaging, without sacrificing resolution. Because shorter sub-exposure times are possible, your equatorial mount won’t need to accurately track over extended periods. The short focal length also lessens equatorial tracking demands. In many cases, autoguiding will not be required.

RASA 11 V2 builds on the legacy of Celestron’s Schmidt Cameras, which allowed astrophotographers to produce images with much shorter exposure times on film in the 1970s.

Today, with CCD sensor sizes as large as film or larger, the RASA 11 V2 offers a 43.3mm optimized image circle to capture pinpoint stars on the largest imaging chips. Optical performance for huge sensors with diagonals of up to 52mm wide is still excellent.

Combine this large image circle with a focal length of just 620mm and you have an instrument suitable for wide-field imaging, creating huge mosaics of the night sky, surveying, and even comet hunting.

Optical Performance
The RASA 11 V2 features optics with 4-element rare-earth glass for images free of false color and aberrations like coma and field curvature. The optical quality and spot size across the entire image circle are unprecedented for an astrograph in this price range—or even that of a much more expensive instrument. The design also provides minimal vignetting.

Advanced Features
RASA 11 V2 utilizes the Ultra-Stable Focus System (USFS). At the heart of this system is a precision linear ball bearing. The bearing serves to minimize focus shift (unwanted lateral motion of the primary mirror during focusing which causes shifting of the image) and mirror flop (movement of the primary mirror when the telescope is pointing to different positions in the sky). The USFS is also compatible with the optional Celestron Focus Motor (#94155-A). The integrated 12V DC MagLev fan reduces cooldown time and provides optimal airflow through the dust filtered optical tube.

Engineered as a complete astroimaging system, every component of the RASA 11 V2 is optimized for peak performance with DSLR and astronomical CCD cameras. Down to the thickness of the glass used in the included fully-multicoated optical window or optional imaging filter, every component of the system has been taken into careful consideration to work together seamlessly. The Dovetail CGE bars on the top of the optical tube provides a connection for use of optional accessories like a guidescope.

The BORG 107FL Telescope Set CR is the premium model BORG telescope, designed for professional astro-watchers. This telescope features a 600mm focal length objective lens that incorporates high-end apochromat fluorite glass elements from Canon Optron, Inc.

Axial chromatic aberrations are suppressed even further with the 107FL objective lens when matched against the 90FL. The BORG 107FL Telescope Set CR is constructed with a lightweight and compactable carbon fiber barrel. Arca-Swiss Quick Release base plates are included for tripod mounting. The BORG 107FL Telescope Set CR is recommended for starry sky, nebula, star cluster, and planet observation.

You can convert this telescope to tele lens by swapping the prism and eyepiece with a BORG camera mount adapter (sold separately).

Main Features

• Fluorite glass elements from Canon Optron, Inc. are incorporated in the optical design for ultimate resolution and minimal axial chromatic aberrations.
• Objective lens optical construction: 2 elements in 2 groups, fluorite apochromat, fully multicoated.
• Robust and beautiful carbon fiber barrel.
• BORG 80Ø barrel system.
• Rack & pinion focusing system.
• Erect prism (included) allows users to observe both on-ground objects and celestial bodies.
• 20mm and 9mm eyepieces included.
• Super lightweight at 3.7 kilograms (including accessories).
• Arca-Swiss Quick Release System tripod plate.
• Objective lenses and major parts are Made in Japan.

'CR' stands for carbon fiber barrel and rack & pinion focusing system.

Camera mount adapters and other camera components are sold separately.

Specifications

The BORG 90FL CR has exceptional optical resolution, accomplished by apochromat fluorite glass elements from Canon Optron, Inc. built in the optical design of the objective lens, and a super tele 500mm focal length and aperture of f/5.6.

A great piece of gear for observing celestial bodies and bird life in the Australian bush and city environments.

The 90mm front element diameter does not hamper the 90FL's extreme compact and lightweight capabilities thanks to the detachable carbon fiber made barrel. Recommended for starry sky, nebula, star cluster, and planet observation. You can convert this telescope to a tele lens by swapping the prism and eyepiece with a BORG camera mount adapter (sold separately).

• Objective lens equipped with apochromat fluorite glass elements from Canon Optron, Inc.
• Objective lens optical design: 2 elements in 2 groups, fluorite, apochromat, fully multicoated.
• Robust and beautiful carbon fiber barrel.
• BORG 80Ø barrel system.
• Rack & pinion focusing system.
• Erect prism (included) allows users to observe both on-ground objects and celestial bodies.
• 20mm and 9mm eyepieces included.
• Lightweight construction of 3 kilograms (including accessories).
• Arca-Swiss Quick Release System tripod plate.
• Objective lenses and major parts are Made in Japan.

'CR' stands for carbon fiber barrel and rack & pinion focusing system.

Camera mount adapters and other camera components are sold separately.

Main Features

PlaneWave CDK 12.5 Fused Silica

Capturing the most stunning astrophotographs possible is something our team is passionate about. From design to manufacture, our goal with the Corrected Dall-Kirkham (CDK) 12.5″ telescope was centered around performance and ease of use. The PlaneWave CDK 12.5 Fused Silica is an incredible breakthrough in telescope technology and produces no off-axis coma and no off-axis astigmatism. Additionally, the PlaneWave CDK 12.5 Fused Silica provides a perfectly flat field so your astrophotographs will have stunning clarity from corner to corner of the image without field curvature degrading the photos. Offering the simplicity of single-mirror collimation, the stray light control of advanced baffles, structural performance created through finite element analysis (FEA), and decades of telescope design experience, the CDK12.5 is an exceptional diffraction-limited telescope. CDK12.5 users can experience pinpoint stars edge-to-edge and a 70 x 70 arcminute field of view when using large camera sensors. When equipment fades into the background and simply performs, the astrophotography experience becomes even more fun and rewarding!

The PlaneWave CDK 12.5 Fused Silica is a 12.5 inch (0.32 m) f/8 Corrected Dall-Kirkham Astrograph telescope. The telescope has a closed carbon fiber tube, with 3 cooling fans ejecting air from the back of the telescope. The PlaneWave CDK 12.5 covers a 52 mm field of view without any field curvature, off-axis coma, or astigmatism. The instrument weight is 21kg and comes standard with the large capacity 2.75 inch Hedrick focuser.

Technology

The CDK Optical Design

The CDK telescope is based on a new optical design developed by Dave Rowe. The goal of the design is to make an affordable astrographic telescope with a large enough imaging plane to take advantage of the large format CCD cameras of today. Most telescope images degrade as you move off-axis from either coma, off-axis astigmatism, or field curvature. The CDK design suffers from none of these problems. The CDK is coma free, has no off-axis astigmatism, and has a flat field. The design is a simple and elegant solution to the problems posed above. The CDK consists of three components: an ellipsoidal primary mirror, a spherical secondary mirror and a lens group. All these components are optimized to work in concert in order to create superb pinpoint stars across the entire 52mm image plane.

Optical Performance

Shown are two simulations showing the CDK’s stunning performance. The first is a diffraction simulation and the second is a spot diagram. In both simulations the small squares are 9×9 microns, about the size of a CCD pixel. In the diffraction simulation the star images on axis and off-axis are nearly identical. In the spot diagram 21mm off-axis the spot size is an incredible 6 microns RMS diameter. This means stars across a 52 mm image circle are going to be pinpoints as small as the atmospheric seeing will allow.

Both of the simulations take into consideration a flat field, which is a more accurate representation of how the optics would perform on a flat CCD camera chip. For visual use some amount of field curvature would be allowed since the eye is able to compensate for a curved field. The diffraction simulation was calculated at 585nm. The spot diagram was calculated at 720, 585, and 430nm. Many companies show spot diagrams in only one wavelength, but you cannot see the chromatic performance with only one wavelength.

Comparison: CDK vs. Ritchey Chrétien

The simulations shown compares the optical performance of the CDK design to the Ritchey Chrétien (RC) design. The Ritchey design was popularized as an astroimaging telescope due to its use in many professional

observatories. Although very difficult and expensive to manufacture and align, the Ritchey is successful in eliminating many of the problems that plague many other designs, namely off-axis coma. However the Ritchey does nothing to eliminate the damaging effects of off-axis astigmatism and field curvature.

The CDK design tackles the off-axis coma problem by integrating a pair of correcting lenses into a two mirror design. The beauty is that this design also corrects for astigmatism and field curvature. Because the lenses are relatively close to the focal plane (unlike the Schmidt corrector plate found in various Schmidt Cassegrain designs), and because these lenses work together as a doublet, there is no chromatic aberration. The CDK offers a wide aberration-free, flat field of view that allows the user to take full advantage of the very large imaging chip cameras in the market place today.

Having an aberration free telescope design means nothing if the optics cannot be aligned properly. Many Ritchey owners never get to take full advantage of their instrument’s performance because the Ritchey is very difficult to collimate. Aligning the hyperbolic secondary mirror’s optical axis to the optical axis of the primary mirror is critical in the Ritchey design, and the tolerances are unforgiving. The secondary mirror of the CDK design is spherical. It has no optical axis and so the centering tolerance of the CDK secondary mirror is comparatively huge. With the help of some very simple tools, the CDK user will be able to set the secondary spacing, collimate the optics and begin enjoying the full performance potential the instrument has to offer within a few minutes.

The drastic difference in performance between the CDK and the RC is apparent. The biggest component that degrades the off-axis performance of the RC is the defocus due to field curvature. In many diagrams shown by RC manufacturers, the diagrams look better than this because they are showing a curved field. This is fine for visual use because the eye can compensate for some amount of curvature of field. But CCD arrays are flat and so in order to evaluate the performance a spot diagrams and/or diffraction simulations requires a flat field as shown.

PlaneWave CDK 12.5 Specifications

OPTICAL SYSTEM

SECONDARY MIRROR

PRIMARY MIRROR

LENS GROUP

SHIPPING

INCLUDED ACCESSORIES

Collimation and Spacing Instructions

The Rowe-Ackermann Schmidt Astrograph (Celestron RASA 36), is a cost-effective optical system for space surveillance, Space Situational Awareness (SSA), other scientific applications, and advanced wide field astroimaging. It offers unprecedented value in aperture, speed, field of view, and optical performance. The RASA design has a convenient external prime-focus image capture location with a flat focal plane, providing small spot sizes to the edge of a wide field. The result is images free of optical defects like field curvature, off-axis coma, and astigmatism.

The 36 cm aperture version is the largest RASA Celestron manufactures; it is the biggest and fastest (f/2.2) optical instrument of its kind available off-the-shelf. Unlike most telescopes, which only focus visible light (400-700 nm), the RASA 36 cm focuses an extended spectral range (400-900 nm), allowing a brighter signal to be detected by a camera sensor. The RASA 36 cm also features a redesigned focus system, which ensures easy and stable focusing.

RASA 36 c sample back-focus distance (77.5 mm) accommodates a wide variety of imaging sensors. A custom camera adapter can be added for a field of view up to 4.4 degrees.

Important freight requirement RASA 36 is a professional-caliber, high-precision instrument. It is manufactured and aligned to an exacting standard to provide exceptional optical performance. The telescope has been packaged to ensure it retains alignment and resulting performance during transport. However, due to the weight, size, and known stresses of shipping via parcel service, Celestron has determined that the ideal transport is a palletized delivery via LTL truck freight. For all Australian deliveries, Celestron will ship via this method. Please contact us for further freight costs