AGO iDK Astrographs

AGO Imaging Dall Kirkham (iDK) astrographs are high resolution instruments with excellent on and off axis performance.  By combining large aperture, medium focal ratio, corrected optics in a lightweight, stiff, and thermally stable carbon fiber tube AGO has created an instrument capable of capturing stunning images of our universe.

• Optics interferometrically tested as a system

• Fast F6.7 system designed and baffled to cover 16803 size chip

• 11" of back focus to support almost any combination of imaging components

• Excellent coma, astigamtism, flat field performance over 52 mm image circle

• Best-in-class FLI Atlas focuser is standard

• Optec 5 piece 3.5" diameter (stiff!) extension tube set included as standard (0.5" to 6.75" range in 0.25" increments)

• Carbon fiber truss or optional full tube versions available

• Optional Ultra Low Expansion (ULE) mirrors optional

Click here to read about the excellent optical design of AGO iDK astrographs. 

Model Specifications

Model	iDK12.5	iDK16	iDK20
Aperture	12.5"	16"	20"
Focal ratio	6.7	6.7	6.7
Focal length	83.5"	107"	134"
Back focus	11"	11"	11"
OTA type	Truss*	Truss*	Truss*
Primary mirror	conical primary mirror, Supremax 33 substrate
Fans (blowing air into OTA)	3 x 60mm fans	3 x 80 mm fans	4 x 80 mm fans
Secondary diameter	6.0"	7.2"	8.4"
Focuser (included)	FLI Atlas digital focuser (includes Optec extension tube to Atlas adapter)
Extension tubes	Optec 5 piece 3.5" extension tube set included with OTA.  Adjustable in 0.25" increments over a range from 0.5" to 6.75".  A 0.125" spacer is included to increase spacing resolution to 0.125".
Corrector	85mm two element, broadband AR coated	100mm two element broadband AR coated
Mirror Coatings	High Reflectivity Aluminum
Baffling	primary and secondary baffles, baffled for 16803 size chip
Dovetail	Massive, thermally compensated dovetail plate include
Tube length	30.5"	37"	45"
Tube weight with dovetail &  focuser	approx. 48 lbs	approx. 88 lbs	approx. 135 lbs
Price	$10,695	$19,995	$29,995
Delivery	approx 3-4 months
Shipping	contact AGO

*Full tube option available

The AGO iDK astrograph line includes a very manageable 12.5" F6.7 model and two observatory class F6.7 models in 16" and 20" apertures.  Each model has a Supremax 33 conical primary mirror and Supremax 33 secondary mirror with high reflectivity aluminum coatings on both mirrors.  These tube assemblies contain optics that are figured and tested as a system to guarantee excellent performance. 

Optical Design

AG Optical Dall Kirkham astrographs provide pinpoint stars (sub 6 micron RMS spot size, 52mm image circle) over large fields of view at a moderate F6.7 focal ratio.  This exceptional wide field performance is made possible by the use of a two element corrector which reduces coma, field curvature and astigmatism to negligible levels.

Below is a flat field, polychromatic spot diagram for the AGO iDK16 (imaging Dall Kirkham) telescope.  This system provides 16" of aperture at a moderate focal ratio of F6.7 (2720mm focal length).  The circles around the spot diagrams represent the size of the Airy disk and clearly illustrate the excellent level of correction achieved by this system.

0.55 degrees off axis (52mm diameter circle)

On axis

Each AGO iDK corrector is permanently aligned and has multilayer broadband AR coatings (<0.5% reflection) on each optical surface.  The corrector provides a 52mm + diameter circle of pinpoint stars capable of covering chips as large as those found in 16803 cameras.

Stray light is effectively controlled through the strategic placement of baffles at the primary and secondary mirrors.  As an added measure, the interior of each AGO iDK is lined with a flocking material that is extremely effective at trapping stray light. 

The combination of an excellent optical design, top quality components, and careful assembly ensure that each AGO iDK astrograph will provide outstanding performance where it counts..... at the chip of your CCD camera.

Optical Testing

AGO is committed to delivering telescopes that consistently offer performance second to none.  To meet this objective each set of iDK optics is interferometrically tested as a system in autocollimation.  The type of testing is time consuming and expensive but it essentially guarantees that the optics will provide outstanding performance and realize the potential of the excellent design.

Back Focus

AGO has designed our iDK to be CCD imaging platforms capable of the highest performance.  Serious CCD imagers use a wide range of accessories to get that perfect image and finding adequate back focus is always a challenge.  With the availability of image rotators, off axis guiders, adaptive optics and various filterwheels back focus is rapidly consumed.  Each AGO iDK has approximately 11" of useable back focus which is sufficient for nearly any image train combination.  

A variety of tube extenders and adapters are available to help you dial in the perfect position for your CCD imaging train.  Please do not hesitate to contact AGO to discuss your specific needs.

Optec makes AP2.7" and DSI 3.5" extension tubes in multiple lengths that allow extension lengths from 0.5" to 6.75" in 0.25" increments.  Please click here to see available combinations.

Focuser

AGO has selected the FLI Atlas low profile focuser as standard equipment for our iDK astrograph line.  This focuser is capable of carrying heavy camera loads and is extremely precise offering repeatable, predictable automatic focusing.  Its digital control system allows automatic focusing of stars and perfectly complements an AGO iDK astrograph.  Furthermore, the low profile of the Atlas focuser allows each AGO iDK astrograph to have a generous amount of back focus (approximately 9" beyond that used by the focuser) giving astrophotographers maximum flexibility when it comes to selecting imaging train equipment.

Tube Assembly

The tube used for our iDK astrographs is designed to provide a high level of thermal and mechanical stability.  Carbon fiber is used in both the truss and tube versions of our iDK scopes to ensure that focus stability is maintained over a wide range of temperatures.   A extremely stiff and very expensive Nomex Honeycomb core carbon fiber composite tube is used for our full tube iDK scopes. 

 

AGO has also designed the tube assembly to allow the user to collimate both the primary and secondary mirrors while not affecting the critical spacing between the secondary mirror and the corrector element.  Users can completely disassemble the OTA when the time comes to clean or recoat the optics.  Through innovative design and precise execution of the tube mechanics, the secondary to corrector element spacing will be precisely repeated when the user reassembles the scope.

All of the aluminum parts within the tube assembly are precision machined from 6061 aluminum and are anodized to provide a durable, wear resistant finish.  Stainless steel fasteners are used exclusively to prevent corrosion.

iDK backplate on CNC mill, made from 6061 aluminum

Three 12 vDC fans are located behind the primary mirror to help the primary rapidly achieve and maintain thermal equalibrium with the ambient air.  The speed of these fans can be adjusted as circumstances dictate.

Thermal Control

AGO includes cooling fans with manual speed control as standard on all of its iDK telescopes to help speed the cooling of the primary mirror.

For AGO customers who desire more control of the cooling fan system and would like the option of adding heaters in strategic locations where dew has a tendency to form (such as the secondary mirror) AGO is proud to offer the AGO Thermal Control System based on the Kendrick Premier Digital Controller.

The Kendrick Premier Digital Controller is the most advanced controller of its type available and allows users to control a thermal control system comprised of fans and anti-dew heaters using a hand controller or a PC-based software application.   Click here to learn more.