Askar 103APO F/6.8 apochromatic refractor

Askar 103APO F/6.8 apochromatic refractor

The Askar 103APO is a 103mm aperture, 700mm focal length, and 6.8 native focal ratios OTA.

In astrographs, the size of the aperture has a significant impact on observability and image quality. The aperture of 103mm 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.

Askar 103APO adopts a triplet air-spaced APO lens design, including one piece of ED glass.

APO(Apochromatic) telescope is a type of telescope with the ability to correct chromatic aberration. Chromatic aberration is a common optical aberration that causes colored edges or blurring around the edges of objects in an image. Other telescopes have relatively simple optical designs and are prone to chromatic aberration, especially at high magnification or in observations where color accuracy is required. However, APO telescopes employ 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. Chromatic aberration occurs because light of different wavelengths refracts differently when passing through a lens, leading to color separation and a decrease in image quality. ED glass has special optical properties that help reduce stray light and effectively minimize chromatic aberration.

The Askar 103APO not only adopts a triplet lens design (while budget astrographs on the market typically use doublet), but it also has an ED glass to further enhance image quality.

In addition to the carefully designed lens itself, every aspect of the Askar 103APO is dedicated to providing a better shooting experience for users.

All the inner of the Askar 103APO's dew shield is covered with matting felt, while the inner walls of the main tube are coated with matting paint and equipped with the internal baffle. This effectively reduces light scattering and reflection inside the OTA, thus enhancing the brightness, contrast, and resolution of the observed targets.

Each piece of Askar 103APO is equipped with a unique name ring for identification, making each Askar 103APO telescope exclusive to its owner.

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 and protecting the lens itself.

On the Askar 103APO, there are a total of two finder bases. Each side of the focuser is equipped with a finder base. Many users have expressed concerns about the limited space for installing additional astronomical accessories along the use. To address this, we have specially set finder bases on both sides of the focuser. This not only eliminates the need for disassembly when changing the position of the finderscope but also provides additional mounting positions for other astronomical accessories.

The handle of the Askar 103APO has a special slot design, making it also a base for installing a finder scope. The handle itself is sturdy and durable.

The overall design of the tube rings is lightweight, with a total weight of only 750g. The thumb screw of the tube ring allows for easy opening and locking. At the same time, the raised base creates more space to accommodate astronomical accessories. In everyday use, the convenience of each step is taken into consideration.

The dovetail plate is the standard Vixen dovetail plate, compatible with most equatorial mounts and bases on the market. We have also made additional extensions and hole position designs, the length reaching up to 290mm, making it more convenient for balancing on the equatorial mount. With the slot on the handle, the spacing between the tube ring can be adjusted as desired. Additionally, there is also a Losmandy dovetail plate available for purchase, to be used with different equatorial mounts.

The detachable main tube design makes it possible for an OTA to down the focal ratio of 4 from the native F6.8. It can also be used for observations with binoviewer.

The Askar 103APO has three optional advanced accessories: a 1x flattener, a 0.8x reducer, and a 0.6x focal reducer. All three accessories have built-in 2" filter threads for direct filter installation. Additionally, they are equipped with M54/M48 adapters, and the 0.6x reducer includes an additional M68 adapter ring for convenient connections.

The 1x flattener does not change the telescope's focal ratio itself. After connecting with the Askar 103APO, it still maintains a focal ratio of 6.8. The flattener corrects field curvature and coma, resulting in flatter field edges and finer star points.

The 0.8x reducer can bring the Askar 103APO's focal ratio down to F5.4. 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.

The 0.6x reducer can bring the Askar 103APO's focal ratio down to F4 while also providing field flattening. Askar 103APO adpots a detachable tube design, where the rear part of the tube can be removed when using the 0.6x reducer, allowing the telescope to have the necessary length to achieve an F4 focal ratio.

Thanks to the detachable lens tube design, the Askar 103APO can be used for observations with binoviewer.

In terms of visual observations, the Askar 103APO pays great attention to observation quality. It can easily achieve focus when connected to 1.25" or 2" diagonals or various eyepieces.

In terms of the focuser, Askar 103APO is equipped dual-speed rack and pinion large 3.3-inch rigid focuser, which can be compatible with most motorized focusers on the market. There is also a high-precision scale on the 10cm 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.

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 easily secure even under high loads.

The telescope interface at the rear comes with a 1.25"/2" adapter.

Specifications

• Diameter: 103 mm.
• Focal length: 700.4 mm.
• Focal ratio: F/6.8.
• Optical design: air-spaced apochromsatic triplet with central ED lens.
• Total length: 600 mm with dew-shield fully racked in, 711 mm with dew-shiled fully racked out.
• Weight:  4.75 Kg OTA only, 5.5 Kg with rings and dovetail installed.
• In the box: Askar 103APO refractor with rings, top handle, Vixen/GP dovetail plate 290 mm long, Oxford cloth case

Size

Optical design and performances