Askar 140 mm f/7 Triplet APO - EDT Design - 3.5 inch RAP focuser with optical test

Askar 140 mm f/7 Triplet Apo - EDT Design - 3.5 inch RAP focuser

Whether you´re an amateur astronomer or a professional astrophotographer, the Askar 140APO will provide you with a high-quality user experience and help you go deeper into the mysteries of the universe.

The Askar 140APO is an OTA with 140 mm aperture, 980 mm focal length, and f/7 native focal ratio

The aperture of 140 mm gives it an inherent advantage in terms of light-gathering power, resolution, brightness, and contrast, allowing the photographer to gather more light and present more details and brighter objects in the image. Along with more light coming into the astrograph, the limiting magnitude can reach 12.5.

The Askar 140APO adopts a triplet air-spaced APO lens design, including one piece of ED glass.

The Askar APO series employs special optical designs and multiple lens elements to correct chromatic aberration, naturally providing higher-quality object details and color accuracy.
In the refractor´s element structure, increasing the number of lens elements and designing lens combinations can effectively improve chromatic aberration correction. However, this also means increased production costs and design complexity.
ED glass, also known as low-dispersion glass, is a type of optical glass specifically designed to reduce chromatic aberration.
As a large aperture, long focal ratio telescope, the Askar 140APO was designed with portability in mind. The shortest overall length is only 735 mm, the net weight is 9.2 kg, and the gross weight is 10.9 kg (including the handle, tube ring, and dovetail plate).

The retractable design of the dew shield, along with the enlarged locking screws, provides convenient usage. The dew shield serves the purpose of protecting the lens from the impact of external and internal light.
The Askar 140APO has an overall lightweight design for the tube ring, with an overall weight of 1.7 kg. The thumb screws enable easy opening and locking of the tube rings. Meanwhile, the base of the tube rings is heightened, providing more space.
The handle of the Askar 140APO has a special slot design, making it also a base for installing a finder scope. The handle itself is 220 mm long.
The dovetail plate of the Askar 140APO is the standard Losmandy style dovetail plate, which is compatible with most equatorial mounts and bases on the market. Askar extended the length and added screw holes, making the length 300 mm, which is easier to balance on the mounts. With the slotted handle, the spacing between the tube rings can be adjusted as desired.

Integrated tube extension

It is worth mentioning that the rear lens tube of the Askar 140APO has an integrated retractable design. We strengthen the overall stability and ensure that the optical axis will not be affected when the lens tube is stretched, thus guaranteeing the quality of the image. The retractable part also features a rudder-type locking ring that makes it easy to loosen or tighten.



When the lens tube is contracted, the Askar 140APO can be used with a binoviewer for visual observation. When the lens tube is stretched, the 140APO can be equipped with a specific reducer or flattener for imaging or a diagonal and eyepiece for observing.

In terms of visual observation,it can easily achieve focus when connected to 1.25" or 2" diagonals or various eyepieces. Because of the retractable lens tube design, it can also be attached to a binoviewer for visual observation.

The focuser of the 140APO

In terms of the focuser, the Askar 140APO is equipped with a dual-speed rack and pinion large 3.5-inch rigid focuser, which can be compatible with most motorized focusers on the market. There is a high-precision scale on the 10-cm focusing travel. The entire focuser barrel is CNC-machined with an anti-reflective internal design and matting paint, providing extra measures to eliminate stray light.
There are two finder bases on both sides of the focuser, which not only eliminates the need for disassembling when changing the position of the finder scope but also provides additional mounting positions for other astronomical accessories.
The rear of the focuser features a 360° high-precision big rotator, along with precise scales for convenient adjustment and saving of rotation angles, enabling precise rotation. It is also equipped with an enlarged rotator locking screw that can be easily secured even under high loads. The telescope interface at the rear comes with a 1.25"/2" adapter.

The entire Askar 140APO tube is crafted using high-quality CNC machining with anodized and surface spray paint treatments. The orange accents on the ivory-white tube add a bright and eye-catching touch, presenting a stylish and elegant overall appearance.

Accessories: 0.8 reducer and 1.0 flattener

The Askar 140APO has two optional accessories: a 1x flattener and a 0.8x reducer. Both accessories come with a built-in 2" filter thread for direct filter mounting. The 0.8x reducer is equipped with M54/M48 adapters, and the 1x flattener is equipped with M68/M54/M48 adapters for easy connection.
The 1x flattener does not change the telescope´s focal ratio itself. After connecting with the Askar 140APO, it still maintains a focal ratio of f/7. The flattener corrects field curvature and coma, resulting in flatter field edges and finer star points.
The 0.8x reducer can bring the Askar 140APO´s focal ratio down to f/5.6. This is a standard reducer with field flattening capabilities as well. A shorter focal ratio allows the OTA to have a wider field of view and faster exposure times, making it suitable for capturing large areas of nebulae, star clusters, and faint, fast-moving celestial objects.
If you prefer to screw your own correctors to the focuser, you will find two adapters in the accessories section. M92A-M88i turns the M92 thread into an M88x1 thread, but more versatile is OAZ3-Flat25, which adapts to an M68x1 female thread.

This is how we hand over the apo to the stargazer:

Every single APO is checked in our technical department before it is put into storage in order to guarantee consistently high product quality.

The mechanics are tested and the focuser is optimally adjusted.

The lens is cosmetically checked and cleaned. We also check that all counter screws are correctly tightened. These often loosen during transportation.

The optics are collimated and the result is checked on the optical bench. The telescope is given a serial number.

An optical test is carried out, which is enclosed with the telescope (star images and ronchi image on the optical bench in autocollimation).

Only then are the telescopes handed over to the warehouse and prepared for dispatch.

Technical Information

Teleskop-Service has collected a lot of helpful information about refractors and provided it in English as a PDF file: refractors.pdf

Safety informations: PDF Download