Askar N210 - 210/714 mm f/3.4 Newtonian Astrograph - with optics test

Askar N210 - 210/714 mm f/3.4 Newtonian Astrograph - with optics test

Following the Askar N160, ASKAR updates the same product line with a larger-aperture Newtonian reflector telescope - the Askar N210. This new model boosts the clear aperture to 210 mm, and while retaining the solid craftsmanship and excellent handling of the N160, it further enhances light-gathering capability and imaging quality. Specifically designed for deep-sky astrophotographers who demand higher image quality, it offers a cost-effective choice for those looking to upgrade to a large-aperture Newtonian telescope.

Properties

The N210 features a large 210 mm aperture and a focal ratio of f/3.6. When used with the included 2-inch 0.95x coma corrector, the system focal ratio is improved to f/3.4, which shortens exposure times while, due to excellent star images up to the edge, achieving perfect compatibility with APS-C format for deep-sky imaging.



Larger aperture with approximately a 78% increase in light-gathering area

Compared with N160, the N210 delivers approximately 78% larger light-gathering area, bringing a substantial boost in light-gathering capability. Light-gathering area is a critical factor in deep-sky photography, greater light throughput captures more faint deep-sky signals, effectively boosting image SNR and detail resolution, producing cleaner, more transparent images.

At the core of the optical system, the primary mirror features a high-precision parabolic design. Relying on rigorous grinding and testing, it effectively eliminate spherical aberration. This ensures that star points across the entire frame remain uniform, solid, sharp, and transparent which perfectly meeting the stringent quality demands of deep-sky imaging.



Standard 2-inch 0.95x Coma Corrector

The included 2-inch 0.95x coma corrector features a triplet air-spaced design, effectively correcting coma as the predominant aberration and ensuring sharpness from the center to the edge of the frame, delivering sharp and clear images.

The corrector features a threaded locking design for a secure connection to the focuser, offering greater stability than traditional push-fit designs.



Primary and Secondary Mirror Glass Material

Both the primary and secondary mirrors are made of high-borosilicate glass, which has an extremely low coefficient of thermal expansion and strong adaptability to temperature changes. This effectively prevents mirror deformation or optical axis misalignment caused by temperature variations. The mirror surfaces are coated with enhanced aluminum for high reflectivity, ensuring bright, clear imaging with abundant fine details.



Primary Mirror Design

The primary mirror employs a dedicated surrounding support structure design that ensures even force distribution and outstanding structural rigidity, effectively improving support stability. This design is particularly optimised for scenarios such as meridian flips, maintaining optical stability even during large telescope position changes, providing reliable mechanical support for long-exposure imaging.

The primary mirror is equipped with three height adjustment knobs and three height locking knobs. The height adjustment knobs allow fine tuning of the primary mirror angle for precise collimation; the height locking knobs secure the primary mirror position after collimation, preventing any shift during subsequent use.



Secondary Mirror Design

The N210 features a newly upgraded, precision-machined one-piece secondary mirror bracket designed for large-aperture imaging. Its reinforced structure significantly enhances stability while maintaining a lightweight design - effectively reducing tube load. This balanced construction provides a rigid yet lightweight foundation, ensuring reliable support for long deep-sky exposures.

Four pre-drilled holes on the secondary mirror bracket allow users to easily install a rainproof cover via screw fixation, offering greater flexibility.

The secondary mirror has a minor axis of 71 mm and a major axis of 100 mm, providing unifrom and ample illumination for APS-C sensors, and ensuring uniform brightness across the entire frame from center to edge.

To suppress stray light and enhance contrast, the N210 features a black nylon-wrapped structure around the secondary mirror. This design slows temperature changes, reduces thermal shock, minimizes condensation risk, and ensures optical stability during long night sessions.

Three tilt adjustment screws are fitted on the bracket base, enabling fine angle adjustment of the secondary mirror. The mirror position can be flexibly adjusted according to shooting needs to further improve imaging accuracy.



Dual-Speed Rack-and-Pinion Focuser

The telescope is equipped with a dual-speed rack-and-pinion focuser, compatible with almost all brands of electronic focusers. The 25 mm focus travel provides ample room for achieving focus.

The focuser body can be rotated entirely, effectively preventing interference when attaching accessories such as an electronic focuser, improving accessory compatibility.

The focuser base equipped with angle adjustment screws and locking screws to ensure precise alignment between the focuser axis and the primary mirror optical axis.



Multi-Function Tube Rings and Dovetail Plate

The tube rings feature a clamshell opening design with large hand-tightened locking screws, that require no additional tools for installation or removal, making operation quick and convenient.

The top handle of the tube rings includes a multi-function finder base slot, which not only facilitates easy carrying but also provides additional mounting positions for other astronomy accessories.

The bottom dovetail plate is a standard Vixen-style dovetail, 400 mm in length, allowing direct connection to most commercially available mounts or tripods, offering excellent versatility and allowing quick setup without extra adapters.



Carbon Fiber Tube

N210 continues the classic red-and-black color scheme of the N series, simple and timeless. The tube is made of high-quality carbon fiber, balancing light weight with structural stability, significantly reducing overall weight while maintaining tube rigidity. The inner tube wall is lined with professional light-baffle felt to effectively suppress stray light.

Carbon fiber has an extremely low coefficient of thermal expansion, effectively resisting temperature variations and preventing tube deformation or focal shift caused by thermal expansion or contraction, ensuring imaging stability.

The side of the tube features a pre-drilled finder base, allowing you to mount a guide scope or other accessories as needed, further expanding observation capabilities and improving efficiency.



The Individual Parts

Important notes to the picture:

1.The focuser base of the Askar N210 is locked at the factory. The base is equipped with six locking screws. If you need to rotate the focuser, be sure to loosen the locking screws before use to avoid mechanical damage.

2.This product has been collimated at the factory. In most cases, it is ready for use right out of the box without extra adjustment. However, due to various uncontrollable factors (e.g., shipping, handling, or other external impacts), slight misalignment may occur. If this happens, please fine-tune the primary mirror collimation to ensure observation and imaging accuracy.



Dimensions, Components, Adjustment Screws

Unless otherwise noted, all measurements are in millimeters.

For alignment, the secondary mirror is adjusted first using the three adjustment screws (Secondary mirror tilt adjustment screw) with a 3 mm hex wrench (last sketch). The clamping screw (Secondary mirror height adjustment screw) should not be loosened here - unless major adjustments are needed - provided the adjustment screws are not too stiff, as otherwise the secondary mirror could rotate unintentionally.

Next, adjust the primary mirror. To do this, first loosen the locking knobs (Primary mirror height locking knob), then align the mirror using the adjustment screws (Primary mirror height adjustment screw), and finally secure it again with the locking knobs (penultimate sketch).



Inserting the Shims

The stainless steel shims are used to fine-tune the working distance when the extension tube is retracted. Filters placed in the optical path, for example, shift the focal point outward, away from the tube.

The Askar N210 comes standard with three different sizes of stainless steel shims. Before attaching your imaging train, you can choose the required shims and install them on the M48 thread of the corrector (see illustration on the right side). By combining different shims, you can fine-tune the back-focus distance to match your setup.

The shims are individually packaged in separate transparent bags.



Connection Options and Working Distance

The working distance of 55 mm is measured from the contact surface on the M48 thread of the coma corrector to the sensor plane and must be maintained for optimal sharpness across the entire image; if necessary, use suitable extension tubes from the "Adapter Extensions" part of the "Adaptors" section (item numbers beginning with TSVF2).

If you wish to work with T2 (M42x0.75) threads, the TSM48i-T2a adapts from M48 to this size; the corresponding extension tubes have part numbers beginning with TST2V.

Astronomy cameras with a working distance other than 17.5 mm can, of course, also be used; in addition to extension tubes and adjustment rings with fixed lengths or thicknesses, variable-length tubes can also be used, but their rotation must be locked securely enough, otherwise it may come loose and become misaligned.

Cameras with a special lens mount - primarily a bayonet mount - are connected using a suitable adapter and should then maintain the correct working distance.



Locking Screw

The locking screw at position 4 is used to secure the draw tube once it has been set to the desired position. For ease of use, it is designed as a knurled thumb screw; therefore, the drawing is primarily helpful if it has come loose or if you have removed it - perhaps because you are using an electronic focusing motor, for which the internal threads at the other positions are suitable - and now need it again.



Electronic Focuser Installation

This guide shows how to connect a ZWO EAF electronic focuser, but many other brands can also be used.

1 Remove the locking screw.
2 Remove the coarse adjustment knob by loosening the set screw with a 2 mm Allen wrench.

3 Place the motor mount in position and insert the standard M4 screws into the holes shown, but do not tighten them yet.

4 Select the matching flexible coupling and tighten the locking screw on the side of the focuser.

7 Finally, tighten the M4 mounting screws.
6 Tighten the EAF mounting screws.
5 Insert the EAF (optional) into the flexible coupling and tighten the locking screw at the end of the coupling.

- OTA
- Coma corrector
- M58 to M48 adapter
- Tube rings
- Multifunctional handle
- Dovetail bar
- Set of shims (2 each of 0.1 mm, 0.2 mm, and 0.3 mm thickness)
- Manual
- TS Star Test

Safety informations: PDF Download