The newest instruments are the 14", 16" and 20" Allira Series™ equatorial fork mounted catadioptric telescopes, available in either the f8.0 or the f5.5 version, or can be purchased with both focal ratios. Perfectly suited for high resolution wide field CCD imaging and astrophotography the instruments will challenge and even outperform the majority of the long standing market leaders of astronomical instrumentation manufactured anywhere in the world, including the leading manufacturers of Ritchey-Chretien telescope systems.

These features, coupled with active computer controlling makes the Allira Series™ of telescopes ideal for the computerised observatory and also for manual operation.

Allira Series™ 14" Telescope.

The Allira Series™ Optical System.

The 14" System.
14" clear diameter, Allira Series™ widefield optical design. Available in both f8.0 (2845mm focal length) with 1.2 degrees fully corrected flat field, and/or f5.5 (1956mm focal length) by interchanging corrector system. Either, or both focal ratios can be purchased.

The 16" System.
16" clear diameter, Allira Series™ widefield optical design, Available in both f8.0 (3251mm focal length) with 1.0 degrees fully corrected flat field, and/or f5.5 (2235mm focal length) by interchanging corrector system. Either, or both focal ratios can be purchased.

The 20" System.
20" clear diameter, Allira Series™ widefield optical design. Available in both f8.0 (4064mm focal length) with 0.8 degrees fully corrected flat field, and/or f5.5 (2794mm focal length) by interchanging corrector system. Either, or both focal ratios can be purchased.

• Total optical component accuracy is better than 0.066λ (1/15λ) RMS wavefront.
  Strehl Ratio greater than, or equal to 0.80.

• Diffraction limited flat field.

• At f8.0 the image size at the focal plane is 60mm diameter for the 14", 16" and 20" telescopes.
  At f5.5 the image size at the focal plane is 45mm diameter for the 14”, 16” and 20” telescopes.
  Please note that the field is truely flat without obscuration over these entire areas, unlike the majority of competing products.

• The corrector systems are set prior to shipping from factory, or can be interchanged by the telescope operator. The telescope can be purchased in either the f8.0 and/or the f5.5 variant. The alternative teleconverter can be purchased at any time later if required.

• The primary mirror is manufactured from precision annealed Pyrex, Al+SiO2 overcoated, fixed location and has the ability to be independently collimated.

For higher precision use, the primary mirror can be manufactured from AstroSitall glass as an optional extra.
• The secondary mirror is manufactured from precision annealed Pyrex, Al+SiO2 overcoated, fixed location and has the ability to be independently collimated.

For higher precision use, the secondary mirror can be manufactured from AstroSitall glass as an optional extra.
• The f8.0 system has a two element lens corrector system, fixed location and has the ability to be independently collimated. The f5.5 system has a three element corrector which is interchangeable. All lenses are Broad Band AR Coated operating at 450nm to 900nm. The f8.0 system requires a 95mm long adaptor which is fitted between the main OTA tube end casting and the focuser to achieve focus. The adaptor is supplied with the teleconverter option.

• Backfocus distances (measured from the fully racked in focuser to focal plane):
  14" at f8.0 is 78mm, at f5.5 is 182mm
  16" at f8.0 is 81mm, at f5.5 is 185mm
  20" at f8.0 is 80mm, at f5.5 is 184mm

• Lightweight optical components.
• All optical components have the ability to be independently collimated (radially, laterally and in separation distance).
• All optical components are baffled to reduce the effects of scattered light.
• Interferogram supplied with all complete tube assemblies.

The Optical Tube Assembly.

• Full carbon fibre tube.
• Access hatch on lower end of tube to enable easy access to the primary mirror.
• Lightweight 4 vane tensioned small profile secondary support system.
• The 14" and 16" systems have 9 point primary mirror flotation system. The 20" system has 18 point primary mirror flotation system.
• Integral dewcap/lightshield.
• Primary mirror cooling system with variable speed fans.
• The overall design enables the highest possible degree of collimation to be achieved at all times.
• External Accessory Bars located along the top and bottom and along the full length of main tube to enable the fitting of on axis accessories and counterweights. Pairs of M6 holes are located along the entire length of the Accessory Bars as attachment points. Please see the Telescope Accessory Mounting Systems notes as below.
• Please note that the complete optical tube assemblies can be purchased as special order without the telescope mount.

The Focuser System.

• 60.0mm bore diameter for the 14" telescope.
• 74.0mm bore diameter for the 16 and 20" telescope.
• Zero shift, fully encased focuser body.
• The drawtube is located tightly on sealed stainless steel bearings.
• 51.0mm total length (fully racked in) for the 14" and 16" telescopes.
• Variable speed stepper motor controlled - the slowest speed is at 0.02mm increments therefore permitting very fine focusing. Robotic control as option.
• Positive drive helical rack and pinion.
• Focus travel (from fully racked "in" to fully racked "out") is 45mm.
• Secondary drawtube is used to permit additional travel length, also with 3 locking screws.
• Main drawtube can be locked with 3 setscrews located radially at 120 degrees apart.
 

Finderscope/Wide Angle Refractor.

• 80mm diameter f3.6 objective doublet.
• Helical rack and pinion low profile, zero shift, manual operation.
• Mounted on sliding dovetail plate.
• Can be independently aligned to main telescope to a maximum of +/-2 degrees offset.

The Allira Series™ Equatorial Fork Mount.

The Equatorial Fork Mount has been designed to provide the capacity of a high precision tracking platform for the optical tube assembly. The fork mount layout has significant advantages over the German Equatorial Mount due to the ability of the fork arms to support both sides of the optical tube assembly. The fork mount also has a significant advantage in that it does not require the telescope to stop and flip reverse across the meridian, which is especially important stand-alone during robotic operations.

The Anssen Allira Series™ 14" and 16" fork mounts features precision cast aluminium fork arms with extremely high sectional rigidity to significantly reduce the effect of flexure and harmonic resonance. The Allira Series™ 20" fork mount is manufactured from steel. For all systems the Centre Section between the fork arms is keyed to each of the fork arms to guarantee alignment and squareness of the R.A. and the Declination shafts. The Declination to RA axis squareness can be finely adjusted to high precision using internal adjustments. The Declination axis squareness to the optical axis can be adjusted to high precision.

The widely spaced fork arms permit increased clearances for observer comfort when observing around the polar regions as well as to reduce the possibility of accessory cable snagging during robotic operation. When the telescope moves through Declination of 90 degrees there is a gap envelope of approximately 320mm between the rear of the focuser and the base of the fork arms.

Specifications and Features:

• Vibration/shock/flexure resistant design and construction promoting maximum stability.
• Main body and components manufactured from precision cast aluminium alloy, 6061 and 5083 grade aluminium alloy.
• A significant amount of effort has gone into the light weighting of all components without compromising strength or rigidity.

• Corrosion, chip and abrasion resistant finishes on all surfaces.
• Drive configuration is roller drive on both axis with adjustable slip clutch. This clutch is also lockable.
• R.A. main wheel is 300mm diameter.
• Declination main wheel is 175mm diameter.
• Chechoslovakian manufactured twin stage high precision planetary gear reducers on R.A. and Declination, handpicked and catalogued from the production line.

• German manufactured stepper motors (if fitted).

• German or Swiss manufactured DC servo motors (if fitted).

• R.A. tracking accuracy is typically +/-1.3 to 1.9 arc seconds (or better) without external intervention.
• Digital optical encoders are fitted to both R.A. and Declination axis, enabling a pointing precision to 15 arc seconds.
• Complete telescope pointing analysis and correction system is available as an optional extra which computes and corrects for the adverse effects of atmospheric refraction, precession polar axis misalignment and a variety of other geometric and flexure phenomena.
• Main polar bearing is tapered roller, 210.0mm outside diameter, 140.0mm inside diameter.
• Secondary polar bearing is tapered roller, 110.0mm outside diameter, 70.0mm inside diameter.
• R.A. shaft is manufactured from high tensile steel, with maximum diameter of 140mm and bright zinc plated.
• Declination bearings are tapered roller 63.0mm outside diameter and 32.0mm inside diameter. There are two opposing bearings per fork arm.
• Perpendicularity (squareness) of R.A. to Declination axis is adjustable.
• Perpendicularity (squareness) of Declination axis to the optical axis is adjustable.
• All internal cabling of drive systems, main telescope focuser and encoder systems. Provisions exist for internal cabling of accessories such as CCD cameras.
• All R.A. and Declination drive system coverplates have secondary coverplates which can be removed so as to enable the fitting of electrical plugs and sockets for accessories. Cabling for these accessories (such as CCD and autoguiders) can then be run inside the mount and down into the pier so as to eliminate cable drag and cable cluttering around the telescope.
• Stainless steel fasteners used almost exclusively with exception to the high stress junction points where high tensile steel fasteners are used.

The Equatorial Wedge.

The equatorial wedge is extremely robust and flexure resistant. The design enables the telescope to operate from anywhere in the world from 0 degrees latitude to 65 degrees latitude. Higher latitude equatorial wedges are available as special order.

Features:

• Fine adjustment in altitude.
• Fine adjustment in azimuth.
• Stainless steel fasteners.
• +/-5 degrees adjustment in azimuth.
• Completely lockable in all positions.
• Will pull apart for shipping purposes.

General Nomenclature.

Strength, Rigidity and Precision of Manufacture.
Maximising strength and minimising total weight has been an important aspect of the design process. The mount is at the limits of existing technology and materials use, whilst maintaining a reasonable asking price for product quality.

Thermal Mechanical Stability.
The basic design concept enables the Allira to be operated successfully over extreme temperature ranges and temperature gradients without affecting the performance or precision of operation. Estimated operating temperature ranges from minimum of -10 degrees Celcius to maximum of +50 degrees Celcius.

Forward Compatibility.
The overall basic design enables the mount and all options to be upgraded at any time as needed by the customer. It is therefore possible to purchase the mount with only basic accessories as needed at the time of purchase, bearing in mind that as needs and requirements increase further accessories can be purchased to increase the performance levels of the product. We expect that many new options will be made available in the near future so as to increase the versatility of the total product. Also, as technology develops in the industry in general newer and higher level options will become available.

Number of Options Available.
A significant number of options are available for both variants of the Allira. The choice can be made by the customer to suit particular requirements. If neccesary during the ordering process we will provide assistance with what is needed.

Number of Drive Controllers Available.
The Allira is compatible with a number of drive controllers and total observatory systems offered by various manufacturers and depend on customer needs and requirements. The customer is not forced to purchase a proprietary drive controller, or any controller at all.

Simple Operation.
Basic processes and operations are well laid out with simple manual access assuming that the majority of the use of the equipment is in total darkness and most probably with the operator wearing protective clothing. During both imaging operations and computer controlled operations it is entirely possible that the operator will rarely need to manually touch the mount which increases time management efficiencies and end image quality. We are aware that during imaging runs and surveillance operations every second can count.