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Home > Altair & APM Telescopes > Cassegrain Telescopes (Premium) > Altair Planeta 250mm Truss Tube Cassegrain - Professional Grade

Altair Planeta 250mm Truss Tube Cassegrain - Professional Grade

Altair Planeta 250mm Truss Tube Cassegrain - Professional Grade
Altair Astro PLANETA 250mm Super Planetary Cassegrain Optical Test Report Altair Astro PLANETA 250mm Super Planetary Cassegrain Optical Test Report Altair PLANETA 250mm F18 Super Planetary Cassegrain Spot Diagram
Price: £3950.00
Incl. VAT 20% ( £658.33 )
Product code: PLANETA-250-F18
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A new concept 10" F18 carbon fibre truss tube Cassegrain telescope, 100% designed and manufactured in UK/Europe, to the highest specification possible.

The Altair Planeta Cassegrain design is a professional observatory grade visual and planetary imaging instrument, suitable for schools, colleges and universities, or advanced amateur astronomers who want the best quality on the market available. Custom apertures and focal lengths are available from F15 to F18 in larger apertures up to 22".

The idea behind this telescope was to build something different, which would perform superbly, while overcoming the shortfalls of other reflector telescopes currently on the market. It is a specialist product which is uniquely made on a per-order basis, and designed for those who want the best quality.

The primary design aims of the Planeta Super Cassegrain are as follows:

1)    Improved thermal management and the reduction of tube convection currents which degrade the image, by using an open-to-air rapid cool-down design as seen in large observatory instruments throughout the world.

2)    The use of an optical design which is optimised for sharpness and resolution at higher powers, and which easily produces the high powers necessarily for planetary observing, with longer focal length eyepieces – which are not only more comfortable to use having more eye relief than short focal length eyepieces, but do not necessarily require a Barlow lens either. (Also ideal for deep sky observing of smaller objects like clusters and galaxies, or splitting double stars).

3)    A design which will fully illuminates a 1.25” eyepiece field of about 24mm without producing any visible coma (an optical aberration present in Newtonians) nor any appreciable field curvature (present in refractors).

4)    A design which has a small central obstruction of 25.5% (63.8mm) and a long central baffle for maximum contrast, giving similar performance to Super APO refractors costing up to 3 or 4x the price, in apertures equal to, or in excess of 7”, on suitable targets at high power, while weighing a fraction as much (about 13kg) to enable the use of a budget mount. The expenditure is therefore concentrated on the telescope OTA, and the optical quality

5)    A design which has a small enough central obstruction of under 30%, extremely effective baffling (with internal flocking), and extremely smooth reflective surfaces, so as to deliver refractor-like contrast and a razor-sharp image.

6)    A design which has a guaranteed pedigree of optical quality supported by an interferogram demonstrating a Strehl ratio of 0.94 or higher in green light, a wavelength the human eye is most sensitive to.

7)    A design which is light enough to be used on most mainstream mounts such as the iOptron iEQ45, Skywatcher HEQ5 or EQ6/Celestron CGEM ranges.

8)    A design which allows the use of the Starlight Feathertouch focuser for the ultimate in smoothness, which can be automated with an optional hand control, and with enough back-focus to use with bino-viewers.

9)    A design which can be collimated quickly and easily.

We have chosen a truss-tube design because of the better thermal characteristics afforded by air circulation around the optics, almost eliminating the contrast-robbing effects of boundary air current layer formation, as well as allowing the optics to come to thermal equilibrium faster.

The optics are made in Europe with a quartz secondary mirror and a Supremax 33 primary mirror. Both mirrors are optimised as a pair in the same optical laboratory and one individual is personally responsible for the mirror polishing and figuring, and final testing of each telescope.

Each optical set is generated and polished as a set and tested several times on a laser interferometry system, before coating in aluminium with a silicon dioxide overcoat. Each telescope comes with an optical test report which takes both primary and secondary mirrors into account as a complete system, unlike competing models which either do not come with a test report or come with a test report showing the quality of the primary mirror only.

Product features and scope of delivery:

  • Classical Cassegrain optical system made by a leading European optical laboratory, to the highest specification and surface accuracy it is possible to achieve.
  • Aluminium Truss tube telescope chassis with accurately CNC machined components (no casting).
  • Optical test report in Green light, guaranteed Strehl of 0.94 at the focuser i.e. combined for both mirrors.
  • 1x 250mm Losmandy dovetail plate included.
  • 2" Starlight Feathertouch Focuser, made in the USA which can be fully automated with optional motor drive system.
  • Quartz secondary mirror with Supremax 33 primary.
  • 24mm flat field image circle.
  • Super-easy collimation combined push/pull adjustment screws on rear mirror.
  • High Quality Transport Case (hand made) worth over £450.
  • All CNC machined baffles and chassis.
  • Inner baffle tube and outer Carbon Dewshield tube are both flocked.
  • Weight 13kg.
  • A washable Lycra shroud is included, which fits over the truss tube in case of stray light.
  • Optional dew heater can be installed on the secondary mirror during build process.

"Altair Astro Super Cassegrain telescope optics are tested many times during production. The wave-front error of the complete optical system (consisting of both primary and secondary mirror as a set) must meet a minimum standard of at least 0.94 Strehl Ratio when exiting the focuser but without flattener). Each telescope is shipped with a screen-shot showing the final interferometric analysis of the wave-front produced by the particular set of optics in the telescope. This screenshot includes a computer-analysis of the wave-front produced on the test bench. Please note, in the interests of accuracy, astigmatism and coma values are not suppressed on the optical test report. Interferogram results can vary slightly with alignment of the optics when tested, ambient vibrations in the laboratory, and with random air currents - though precautions are of course taken to minimise these factors just as in any optical laboratory. The test report is to be treated like a photographic record, and each test report is unique to your telescope."


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