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Altair / GSO RC 8" Ritchey Chretien Astrograph
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Deluxe Ritchey Chretien Astrograph with Carbon Fibre tube
To order this item outside mainland Britain or Highlands & Islands, please contact us.
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- 8" F8 Ritchey Chretien Astrograph
- 2" Dual Speed Linear Bearing Focuser
- Carbon Fibre tube, weight 7.5kg
- Quartz Mirrors with 96% reflectivity
- Multiple internal light baffles
- 2 x Losmandy type dovetail bars
- 1 x Vixen/Synta type dovetail bars
- Options:
- Genuine 2" Starlight Feather Touch dual speed focuser
- 2" corrector for Ritchey-Chrétiens w/o focal reduction
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Altair / GSO RC 8" Ritchey Chretien Astrograph
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Outline
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This is a "deluxe" version of the tried and tested 8" GSO / Orion / Astro Tech
F8 Ritchey-Chrétien with the following features:
- A 2" Dual Speed Linear Bearing Focuser included as standard. It will handle a DSLR or CCD camera, and a light weight filter wheel perfectly well, and is adequate in most imaging situations. Note this focuser has the Linear Bearing, and will outperform most Taiwanese dual speed focusers.
- Or choose an Optional Genuine 2" Starlight Feather Touch dual speed focuser, (shown in the pictures) which outperforms both the standard focuser with zero backlash, greater rigidity and more lifting power. This is intended for customers with heavier large format CCD cameras, filter wheels.
- Low weight, low expansion Carbon Fibre OTA, weight 7.5kg! (16.4lbs) not only giving more accurace tracking but freeing up your mount capacity for other accessories. The use of a carbon fibre weave composite reduces the weight of the optical tube with no loss of strength or rigidity compared to an aluminium tube. It also doesn't store heat like metal, so convection currents are reduced.
- Low expansion Quartz Mirrors with 96% reflective Enhanced coatings with higher reflectivity than standard mirror coatings on other versions of this scope.
- Optional field flattener available, optimised for this optical design.
- 8" aperture true hyperboloid Primary & Secondary Mirrors.
- Multiple internal light baffles line the optical tube.
- 2x Vixen/Synta type dovetail bar included on the top and base of the scope for guide scope attachment.
- Fast efficient cool down time compared to a normal SCT due to the open-tube design.
- This telescope is designed with enough backfocus to use an off axis guider, AO unit and filter wheel. Therefore, to create the most rigid imaging train possible, instead of placing extension tubes after the focuser it's best to place them between the focuser and the rear mirror cell. Therefore 1x 50mm and 2x 25mm large diameter extension rings are included for this purpose, which can be placed between the focuser and telescope (with zero flex), for adjusting your backfocus.
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The Altair RC8 on display at the Opticstar showroom.
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Advantages of RC Astrographs
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This true Ritchey Chretien astrograph is completely optimised for imaging.
Consider these points when choosing a dedicated imaging telescope.
- Aperture, price and weight. A pure two-mirror optical system means zero colour aberration and a large aperture with high resolution compared to refractors costing many times more and weighing many times more, to gain the same resolution, whilst using a reasonably priced mount.
- No mirror shift. Because it has a fixed focuser, the primary mirror flop and resultant image shift issues associated with long focal length SCT telescopes with moving mirrors are avoided. There is no need for mirror locks and the additional problems these bring when it comes to focusing. There aren't any complex internal parts to move the mirrors back and forth while attempting to keep them accurately aligned so there's less to move about.
- Repeatable focusing. Another benefit of a high quality external focuser, is that the mirrors don't have to move relative to each other to focus the telescope, and so because everything remains in place, the focal point doesn't change outside the tube, making it easier for you to achieve repeatable, accurate focusing time and time again. That's essential for imaging.
- A better focuser for a great price. Unlike a standard Crayford focuser, the LBF focuser won't flex as much and it can take a higher load such as a DSLR or filter wheel, without slippage or backlash. That's because it has a longer and more precise steel load bearing surface, which is in contact with the focuser tube along more of it's length, rather than being supported by bearings with small contact points - a common issue with other Crayfords. This steel track focuser surface will not wear unevenly like aluminium-only surfaces on other focusers.
- Easier to mount and guide. The optical tube is very light yet very rigid and strong, minimising flex. With a weight 7.5kg (16.4lbs) this telescope is one of the lightest in this aperture range. It can be carried by a reasonably priced EQ mount like the iOptron iEQ45 45lb capacity mount, along with a guide scope and wide field refractor. Using an EQ6 or CGEM is also possible as long as a very light weight guide scope is used.
- Fastest cool-down time in it's class. Don't spend the whole night waiting for your scope to cool down. Closed tube telescopes with corrector plates such as Maksutovs and SCTs can take so long to cool down that they never reach ambient temperature during the whole night. The RC optical tube is an open design, minimising cool down time compared to SCTs with closed tubes, and three rear cooling fans embedded in the rear mirror cover bring the primary mirror down to ambient temperature as quickly as possible (a battery pack is included or the fans can be powered by a Kendrick controller).
- Contrast and controlling stray light. The internal knife edge baffles and matte black interior ensure high contrast and minimize the intrusion of stray light, reducing background glare on long exposure images. You will never have to to line the interior of this instrument with "flocking paper" to improve contrast - common practise with other imaging reflectors. Because there is no large corrector plate pointing at the sky, it's very rare for condensation or dew to form on the optics and it almost never occurs. However for unusual and extremely dewy conditions, Kendrick dew control system heaters will fit the secondary mirror.
- Optical performance: The surfaces of the Ritchey-Chrétien primary and secondary mirrors are hyperbolic, and are carefully optimised to reduce coma, an optical aberration which results in flared stars at the edges of the photographic field in other Cassegrain designs. The Ritchey-Chrétien design was previously only available in large scale observatory optics, however, as mirror polishing techniques have advanced, they are finally available to the amateur astro photographer at a reasonable price. Further aberrations like field curvature are removed by the field corrector/flattener, available separately, and useful for large CCD sensors, or DSLR users, and is similar to those offered by other manufacturers charging up to four times the price.
- Price and performance for this aperture at an F8 focal length. For the aperture, resolution, and performance, this scope is simply the best value we have been able to source. We do not know of any other large aperture imaging OTA which can deliver results at this focal length which even comes close. Closed tube telescopes with an F10 focal ratio usually cost about 25-30% more. Not only are you paying less money for a genuine RC telescope designed for imaging from the ground up, but you are getting a faster optical system which places less demand on mount, tracking and CCD camera due to shorter exposure times.
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The Eagle Nebula captured by Salvatore Grasso with GSO RC 8.
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The M81 Galaxy captured by Salvatore Grasso with GSO RC 8.
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Notice
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We are constantly checking the accuracy of the technical data. We are prepared
to provide more detailed information on request. Technical data is subject to
change without notice.
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Promotional Offer
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Cash Back on Opticstar
Imaging Products
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updated: 21st February 2012
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Customers who purchase any Altair optical tubes
listed on this page qualify for a 10% cash back on any Opticstar astronomy
cameras purchased at the same time or at a later date.
This offer is valid for 1 year commencing on the date that the Altair
product is purchased from the Opticstar website or the Opticstar showroom.
Any additional purchases at a later date of Altair products that qualify for
this offer will renew the cash back period to 1 full year.
Opticstar astronomy cameras that qualify for this offer include the following:
Once an Opticstar CCD or CMOS camera has been purchased within a year of
the qualifying Celestron purchase, the cash back can be claimed by contacting
Opticstar by email or over the phone quoting the receipt number(s). Please
allow up to 14 days to process the payment.
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Sample Images
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Opticstar DS-145M ICE
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posted: 13th March 2009
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The M20 nebula shot by John Haunton with the Opticstar DS-145M ICE.
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Sample Images
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Opticstar PL-130M CoolAir
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posted: 10th February 2009
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An impressive 9.4 megapixel mosaic of the Moon by Herwig Sulzbacher with
the Opticstar PL-130M.
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Feedback
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We want to hear your comments.
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Sample Images
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Opticstar DS-335C ICE
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updated: 20th August 2010
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The M8 nebula shot by John Haunton with the Opticstar DS-335C ICE.
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Astrophotography
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Opticstar Imaging
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posted: 26th February 2013
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High quality refractor telescopes, bundled with CCD cameras for deepd sky imaging,
planetary video imaging and auto-guiding.
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A&M 80mm f/6 Review
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"Best Of Breed"
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updated: 25th March 2009
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The A&M 80mm f/6 A&M/TMB has been
reviewed in Cloudy Nights
and it has been hailed as the "best of breed". The review concludes by saying "offers
stunning performance while standing out from the crowd, look no further".
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Willmann Bell
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Books for Astronomy
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updated: 15th May 2012
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Acclaimed books from Willmann Bell...
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